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Cerebral Veins

Last Updated: August 23, 2020

Introduction

There are several reasons that the veins of the cerebrum have received little attention in the neurosurgical literature. Earlier studies of these veins have focused predominantly on the lateral surface of the cerebrum and lacked the detail needed for operations on the medial and basal surfaces. Frequent variations in the size and connections of these veins have made it difficult to define a normal pattern, and the nomenclature used to describe the veins has infrequently been applicable to the operative situation. The fact that sacrifice of the major trunks of the deep venous system only infrequently leads to venous infarction with mass effect and neurological deficit is attributed to the diffuse anastomoses between the veins. On the other hand, injury to this complicated venous network may cause severe deficits, including hemiplegia, coma, and death. The cerebral veins may pose a major obstacle to operative approaches to deep-seated lesions, especially in the pineal region under the temporal lobe and along the central part of the superior sagittal sinus. At numerous sites, the displacement of the veins may provide more accurate localizing information on neuroradiological studies than the arteries, because the veins are often more adherent to the brain than the arteries, which are not tightly adherent to the cortical surface as they pass through the cisterns, fissures, and sulci. The ventricular veins also provide larger and more valuable landmarks in the lateral ventricle than the arteries, especially if hydrocephalus—a common result of ventricular tumors—is present, because  the borders between the neural structures in the ventricular walls become less distinct as the ventricles dilate. The cerebral veins are divided into a superficial group and a deep group. The superficial group drains the cortical surfaces. The deep group drains the deep white and gray matter and collects into channels that course through the walls of the ventricles and basal cisterns to drain into the internal cerebral, basal, and great veins. 

The Superficial Veins

Drainage Groups

The superficial veins drain the cortical surfaces. They collect into four groups of bridging veins: a superior sagittal group that drains into the superior sagittal sinus; a sphenoidal group that drains into the sphenoparietal or cavernous sinus; a tentorial group that converges on the sinuses in the tentorium; and a falcine group that empties into the inferior sagittal or straight sinus, or their tributaries (Fig. 4.1). The latter group includes the cortical veins that reach the straight sinus by emptying into the internal cerebral, basal, and great veins. The superior sagittal, sphenoidal, or tentorial group may drain the majority of the hemisphere if its tributaries are large.

Superior Sagittal Group

The superior sagittal group is composed of the veins that drain into the superior sagittal sinus (Figs. 4.1–4.3). It includes the veins from the superior part of the medial and lateral surfaces of the frontal, parietal, and occipital lobes and from the anterior part of the orbital surface of the frontal lobe. There is usually a free segment of vein, 1 to 2 cm in length, in the subdural space between the vein’s exit from its bed in the pia-arachnoid and its entrance into the sinus. These veins may empty directly into the superior sagittal sinus or may join a meningeal sinus in the dura mater en route to the superior sagittal sinus.

Sphenoidal Group

The sphenoidal group is formed by the bridging veins that empty into the sinuses that course on the inner surface of the sphenoid bone (Fig. 4.1). This group, formed by the terminal ends of the superficial sylvian and occasionally the deep sylvian veins, drains the part of the frontal, temporal, and parietal lobes adjoining the sylvian fissure. These veins drain into the sphenoparietal or cavernous sinus and, less commonly, into the sphenobasal or sphenopetrosal sinuses.

FIGURE 4.1. Dural sinuses and bridging veins. A, oblique superior view; B, direct superior view with the falx and superior sagittal sinus removed. A and B, the veins are divided into four groups based on their site of termination: a superior sagittal group (dark blue), which drains into the superior sagittal sinus; a tentorial group (green), which drains into the transverse or lateral tentorial sinus; a sphenoidal group (red), which drains into the sphenoparietal or cavernous sinus; and a falcine group (purple), which drains into the straight or inferior sagittal sinus either directly or through the basal, great, or internal cerebral veins. The veins emptying into the superior sagittal sinus (blue) drain the upper part of the medial or lateral surfaces of the frontal, parietal, and occipital lobes and the anterior part of the orbital surface of the frontal lobe. The veins from the lateral surface that terminate in the superior sagittal sinus are the frontopolar, anterior frontal, middle frontal, posterior frontal, precentral, central, anterior parietal, posterior parietal, and occipital veins and the vein of Trolard, which, in this case, is a large postcentral vein. The veins from the medial surface that drain into the superior sagittal sinus (blue) are the anteromedial frontal, centromedial frontal, posteromedial frontal, paracentral, anteromedial parietal, posteromedial parietal, and posterior calcarine veins. The veins from the orbital surface that drain into the superior sagittal sinus are the anterior orbitofrontal veins. The veins emptying into the sinuses in the tentorium (green) drain the lateral and basal surfaces of the temporal lobe and the basal surface of the occipital lobe. The veins from the lateral surface that drain into the sinuses in the tentorium are the anterior temporal, middle temporal, and posterior temporal veins and the vein of Labbé. The veins from the inferior surface that drain into the sinuses in the tentorium are the anterior temporobasal, middle temporobasal, posterior temporobasal, and occipitobasal veins. The veins that empty into the cavernous or sphenoparietal sinus (red) course along the sylvian fissure and drain the parts of the frontal, parietal, and temporal lobes adjoining the sylvian fissure. These branches are the superficial sylvian vein and its tributaries, the frontosylvian, parietosylvian, and temporosylvian veins. The veins emptying into the straight sinus (purple) or its tributaries drain the part of the frontal and parietal lobes surrounding the corpus callosum and the medial part of the temporal lobe. The area drained by this group corresponds roughly to the limbic lobe of the brain. The veins in this group are the paraterminal, posterior fronto-orbital, olfactory, anterior pericallosal, posterior pericallosal, uncal, anterior hippocampal, medial temporal, and anterior calcarine veins. The right superficial sylvian veins are directed toward the sphenoparietal sinus and the anterior part of the cavernous sinus, and the left superficial sylvian veins are directed further posteriorly toward a lateral extension of the cavernous sinus. The deep sylvian and anterior cerebral veins also empty into the anterior end of the basal vein. The carotid arteries pass through the cavernous sinuses. The meningeal sinuses in the floor of the middle cranial fossae course with the middle meningeal arteries. The medial tentorial sinuses receive tributaries from the cerebellum and join the straight sinus. The basilar sinus sits on the clivus. Pacchionian granulations protrude into the venous lacuane. A., artery; Ant., anterior; Ant.Med., anteromedial; Bas., basilar; Calc., calcarine; Car., carotid; Cav., cavernous; Cent., central; Cer., cerebral; Front., frontal; Front.Orb., fronto orbital; Hippo., hippocampal; Inf., inferior; Int., internal; Lat., lateral; Med., medial; Men., meningeal; Mid., middle; Occip., occipital; Olf., olfactory; Pacci. Gran., Pacchionian granulations; Par., parietal; Paracent., paracentral; Paraterm., paraterminal; Pericall., pericallosal; Pet., petrosal; Post., posterior; Post.Med., posteromedial; Precent., precentral; Sag., sagittal; Sphen.Par., sphenoparietal; Str., straight; Sup., superior; Temp., temporal; Tent., tentorial, tentorium; Trans., transverse; V., vein; Ven., venous.

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FIGURE 4.2. A, superior view. The dura covering the cerebrum has been removed to expose the cortical veins entering the superior sagittal sinus. The branches of the left anterior and middle cerebral arteries have been preserved. The veins entering the most anterior part of the sagittal sinus are directed slightly posteriorly. Those from the midportion of the frontal lobe enter the sagittal sinus at a right angle and, proceeding posteriorly, the veins entering the sinus are progressively angulated further forward. The central sulcus reaches the superior hemispheric border. B, the arteries on the left side have been removed. The veins entering the posterior part of the sagittal sinus are directed forward. Anterior, middle, and posterior frontal, and central and postcentral veins ascend to the superior sagittal sinus. The posterior frontal vein drains the area normally drained by precentral and posterior frontal veins. C, right anterolateral view. The right middle and posterior frontal veins join sinuses in the dura that empty medially into the superior sagittal sinus. The right anterior frontal vein empties directly into the superior sagittal sinus. Yellow arrows are on two dural sinuses on the right and three on the left side. D, left anterolateral view. The left anterior, middle, and posterior frontal and precentral veins do not pass directly to the superior sagittal sinus, but empty into dural sinuses that cross the upper border of the frontal lobe to reach the superior sagittal sinus. Yellow arrows are on four left dural sinuses. E, posterior view. The veins on the occipital lobe are directed forward so that the area below the lambdoid suture is often completely devoid of bridging veins to the superior sagittal sinus. This often allows the occipital lobe to be retracted away from the sagittal sinus without sacrificing any bridging veins. There is an intrasutural bone in each lambdoid suture. F, another specimen. The lambdoid suture has been removed to show the absence of bridging veins entering the posterior part of the superior sagittal sinus. Right postcentral and anterior and posterior parietal veins empty into the superior sagittal sinus. The right occipital lobe has been retracted to expose the tentorium, falx, and straight sinus. There are no bridging veins between the occipital pole and the superior sagittal or straight sinus. Ant., anterior; Cent., central; Front., frontal; Mid., middle; Par., parietal; Post., posterior; Postcent., postcentral; Precent., precentral; Sag., sagittal; Squam., squamosal; Str., straight; Sup., superior; Temp., temporal; Tent., tentorium; V., vein.

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FIGURE 4.3. Venous lacunae and bridging veins to the superior sagittal sinus. A, superior view. A large venous lacunae adjoining the sagittal sinus extends above the bridging veins emptying into the superior sagittal sinus. The veins from the right hemisphere emptying into the superior sagittal sinus are the anterior, middle, and posterior frontal, central, postcentral, and anterior parietal veins. The precentral and central areas are drained by the large central vein. The veins draining the posterior part of the hemisphere are directed forward. B, the large venous lacunae have been removed to show the veins passing below the lacunae to enter the superior sagittal sinus. The left central vein joins the superior sagittal sinus at the upper end of the central sulcus. The right central vein passes forward across the precentral gyrus to join the superior sagittal sinus. C, the frontal lobe is above and the occipital lobe is below. A large venous lacunae covers the central part of the cerebral vertex. D, some of the dura covering the upper surface of another venous lacunae have been removed. Most of the veins draining into the sagittal sinus proceed medially below the lacunae to reach the sinus. E, right lateral view of the sagittal sinus after removal of the lacunae shown in D. The veins entering the sagittal sinus pass below the large venous lacunae. The medial and lateral, frontal and parietal veins often join to form a common stem before emptying into the sagittal sinus. Ant., anterior; Bridg., bridging; Cent., central; Front., frontal; Lat., lateral; Med., medial; Mid., middle; Occip., occipital; Par., parietal; Postcent., postcentral; Sag., sagittal; Sup., superior; V., vein.

Tentorial Group

The tentorial group of bridging veins drains into the sinuses coursing in the tentorium, called the tentorial sinuses, or into the transverse and superior petrosal sinuses in the tentorial margins (Figs. 4.4 and 4.5). This group is composed of the veins draining the lateral surface of the temporal lobe and the basal surface of the temporal and occipital lobes. This group includes the temporobasal and occipitobasal veins and the descending veins, including the vein of Labbé, from the lateral surface of the temporal lobe. These veins converge on the preoccipital notch and, although they may enter the transverse sinus, most of them, except the vein of Labbé, usually course around the inferior margin of the hemisphere to reach the lateral tentorial sinus. The vein of Labbé usually enters the transverse sinus. The bridging veins from the basal surface frequently adhere to the dura mater covering the middle fossa or the tentorium surface before joining the venous sinuses.

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FIGURE 4.4. A-D. Veins of the basal surface. A, the basal surface of the frontal lobe is drained by the frontopolar, anterior and posterior fronto-orbital veins, and the olfactory veins. The anterior fronto-orbital veins empty into the anterior part of the superior sagittal sinus or its tributaries. The posterior fronto-orbital veins empty into the veins below the anterior perforated substance that converge on the anterior end of the basal vein. B, enlarged view. The optic chiasm has been reflected downward to expose the anterior cerebral veins passing above the optic chiasm and being joined by the paraterminal veins that course along the medial surface of the hemisphere below the genu of the corpus callosum. The olfactory, paraterminal, anterior cerebral, and posterior fronto-orbital veins converge on the anterior end of the basal vein. C, basal surface of the temporal lobe. The anterior part of the basal surface of the temporal lobe is drained by the temporosylvian veins that empty into the veins along the sylvian fissure. The right temporobasal veins empty into a tentorial sinus located just medial to the transverse sinus. The area normally drained by the left anterior and middle temporobasal veins is drained predominantly by a long trunk that passes along the long axis of the basal surface and empties at a tentorial sinus. The yellow and red arrows are on the terminal end of veins that empty into the right and left tentorial sinuses shown in D. D, superior view of the tentorial sinuses into which the temporobasal veins shown in C empty. The long vein on the left basal surface empties into the tributary of the left tentorial sinus shown by the red arrow. The temporobasal veins on the right side empty into the right tentorial sinus with multiple tributaries. The vein shown with the yellow arrow in C empties into the tributary of right tentorial sinus shown with a yellow arrow in D.

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FIGURE 4.4. E-H. E, enlarged view of the area below the left anterior perforated substance. The olfactory, anterior cerebral, posterior fronto-orbital, and deep sylvian veins join to form the basal vein. The inferior ventricular vein joins the basal vein at the posterior edge of the cerebral peduncle. F, inferior view of the cerebral hemispheres with the parahippocampal gyri removed to expose the temporal horns and atria. The left fimbria and posterior cerebral artery have been preserved. The left inferior ventricular vein passes above the choroid plexus and through the choroidal fissure located between the fimbria and thalamus. The lateral atrial veins also pass through the choroidal fissure. The lower lip of the calcarine sulcus has been removed on both sides to expose the anterior calcarine veins and calcarine artery and the upper lip of the fissure formed by the cuneus. G, the left fimbria, posterior cerebral artery, and choroid plexus have been removed to expose the inferior ventricular vein crossing the roof of the temporal horn. The anterior calcarine veins, which empty into the vein of Galen, are exposed below the cuneus. H, the floor of the third ventricle has been removed to expose the fornix coursing above the foramen of Monro. The massa intermedia and posterior commissure are exposed. The basal veins pass around the midbrain to join the vein of Galen. Small hypothalamic veins join the anterior end of the basal vein. Ant., anterior; Atr., atrial; Calc., calcarine; Cer., cerebral; CN, cranial nerve; Comm., commissure; For., foramen; Front., frontal; Front.Orb., fronto orbital; Inf., inferior; Int., intermedia; Lat., lateral; Occip., occipital; Olf., olfactory; Paraterm., paraterminal; P.C.A., posterior cerebral artery; Ped., peduncular; Pet., petrosal; Post., posterior; Str., straight; Sup., superior; Temp., temporal; Tent., tentorial; Tr., tract; Trans., transverse; V., vein; Vent., ventral.

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FIGURE 4.5. Tributaries of the transverse and tentorial sinuses. A, posterolateral view. The posterior temporal lobe has been elevated to expose the vein of Labbé and the posterior temporal and occipital veins from the lateral surface joining the transverse sinus and the temporobasal veins from the basal surface of the temporal lobe emptying into the tentorial sinuses. Some veins from the lateral surface of the temporal and occipital convexity do not pass directly to the transverse sinus, but turn medially under the basal surface to empty into sinuses in the tentorium. B, enlarged view. The vein of Labbé is exposed anteriorly. Reaching the tentorial incisura by the posterior subtemporal route may require the sacrifice of multiple temporobasal and occipitobasal veins draining into the tentorial sinuses in addition to the vein of Labbé and other veins from the lateral surface of the temporal and occipital lobes. C, superior view of the tentorium. On the left side, the temporobasal and occipitobasal veins converge on two short tentorial sinuses located just medial to the transverse sinus. On the right side, the vein of Labbé and a posterior temporal vein drain directly into the transverse sinus. Another sinus within the left tentorium (yellow arrow) receives drainage from the cerebellum and passes medially across the tentorium to empty into the torcular herophili. D, the left half of the tentorium has been removed. The bridging cerebellar vein, shown in D with a yellow arrow, empties into the tentorial sinus shown in C with the yellow arrow. E, lateral surface of the right temporal lobe and sylvian fissure in another specimen. The anterior part of the superficial sylvian vein is small and the posterior part that empties into the vein of Labbé is larger. A middle temporal vein that courses along the superior temporal sulcus forms a bridging vein that passes around the lower margin of the hemisphere to empty into a tentorial sinus. The sylvian vein also has connections with the superior sagittal sinus through two anastomotic veins of Trolard: one crosses the frontal lobe and the other crosses the parietal lobe. The temporosylvian veins drain the superior temporal gyrus and empty into the superficial sylvian and middle temporal veins. Mid., middle; Occip., occipital; Pet., petrosal; Post., posterior; Str., straight; Sup., superior; Temp., temporal; Tent., tentorial; Trans., transverse; V., vein.

Falcine Group

The falcine group is formed by the veins that empty into the inferior sagittal or straight sinus, either directly or through the internal cerebral, basal, and great veins (Figs. 4.1 and 4.6). The cortical area drained by the falcine group corresponds roughly to the limbic lobe, a group of convolutions that form a continuous cortical strip that wraps around the corpus callosum and upper brainstem. The largest cortical areas are the parahippocampal and cingulate gyri, but the area also includes the paraterminal, paraolfactory gyri, and the uncus. The veins on the paraterminal and paraolfactory gyri drain posteriorly toward the anterior cerebral vein, which empties into the anterior end of the basal vein. The anterior parts of the cingulate gyrus and corpus callosum are drained by the anterior pericallosal veins, which may join the inferior sagittal sinus or the anterior cerebral vein. The posterior part of the cingulate gyrus is drained by the posterior pericallosal vein, which drains into the great or internal cerebral veins in the quadrigeminal cistern. The area adjoining the isthmus of the cingulate gyrus and the area surrounding the anterior part of the calcarine fissure is drained by anterior calcarine veins, which cross the quadrigeminal cistern to reach the great vein or its tributaries. The medial part of the parahippocampal gyrus and uncus are drained by the uncal, anterior hippocampal, and medial temporal veins, which pass medially to empty into the basal vein in the crural and ambient cisterns.

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FIGURE 4.6. Veins of the medial surface. A, the upper part of the left cerebral hemisphere has been removed to expose the medial surface of the right hemisphere. An anterior pericallosal vein empties into the inferior sagittal sinus. The medial frontal veins draining the area above the cingulate sulcus empty into the superior sagittal sinus. The veins from the medial surface often join the veins from the lateral surface to form a common stem before emptying into the superior sagittal sinus. The veins from the part of the cingulate sulcus bordering the corpus callosum commonly empty into the paraterminal veins or the pericallosal veins. The anterior and posterior septal and medial atrial veins cross the medial wall of the frontal horn, body, and atrium. The anterior pericallosal vein empties into the anterior end of the inferior sagittal sinus. B, the remainder of the left hemisphere has been removed. The medial frontal and parietal veins draining the outer strip of the medial surface empty into the superior sagittal sinus. The veins draining the part of the cingulate sulcus facing the corpus callosum empty into the anterior and posterior pericallosal, paraterminal, and great veins. The posterior calcarine vein drains the posterior part of the calcarine sulcus and commonly empties into the veins on the lateral surface. C, enlarged view. The anterior and posterior caudate and thalamostriate veins in the lateral wall of the frontal horn and body pass through the choroidal fissure between the fornix and thalamus to empty into the internal cerebral veins. The paraterminal vein courses downward in front of the lamina terminalis to empty into the anterior cerebral vein. A posterior pericallosal (splenial) vein passes around the splenium of the corpus callosum and empties into the vein of Galen. D, enlarged view of the inferior sagittal sinus coursing in the lower edge of the falx. An anterior pericallosal vein empties into the anterior end of the inferior sagittal sinus. A small posterior pericallosal vein empties into the vein of Galen. A., artery; Ant., anterior; Atr., atrial; Calc., calcarine; Caud., caudal; Cer., cerebral; Cing., cingulate; CN, cranial nerve; Front., frontal; Inf., inferior; Int., internal; Med., medial; Par., parietal; Paracent., paracentral; Paraterm., paraterminal; Pericall., pericallosal; Pet., petrosal; Post., posterior; Sag., sagittal; Sept., septal; Thal. Str., thalamostriate; V., vein; Vent., ventricle.

Dural Sinuses and Veins

The dural sinuses into which the cortical veins empty are the superior and inferior sagittal, straight, transverse, tentorial, cavernous, sphenoparietal, sphenobasal, and sphenopetrosal sinuses. These sinuses form the terminal part of the superficial cortical venous system. The small sinuses that accompany the meningeal arteries, referred to as the meningeal veins, are also reviewed in this section.

Superior Sagittal Sinus and Venous Lacunae

The superior sagittal sinus courses in the midline beginning just behind the frontal sinuses and grows larger as it continues posteriorly in the shallow groove on the inner table of the cranium (Figs. 4.1–4.3). It may communicate through the foramen cecum with the veins of the nasal cavity. It drains into the transverse sinus at the internal occipital protuberance through a plexiform confluent venous complex, called the torcular herophili, that connects the superior sagittal, transverse, straight, and occipital sinuses. Although the superior sagittal sinus may drain equally to the right and left transverse sinuses or predominantly or wholly to either side, it is usually the right transverse sinus that receives the majority of its drainage. The superior sagittal sinus drains the anterior part of the inferior surface of the frontal lobe and the superior portions of the lateral and medial surfaces of the frontal, parietal, and occipital lobes.

The veins from each cortical area join the superior sagittal sinus in a characteristic configuration (Figs. 4.2, 4.3, and 4.7). The veins arising near the frontal pole are directed posteriorly, in the usual direction of flow within the sinus, at their junction with the sinus. The veins arising from the posterior part of the frontal lobe are directed forward as they join the sinus, in a direction opposed to the direction of flow within the sinus, and those from the intermediate frontal areas join the sinus at approximately a right angle. The terminal ends of the parietal and occipital veins are directed forward and enter the superior sagittal sinus at an angle opposed to the direction of flow. The more posterior veins course anteriorly and slightly inferiorly to enter the lower margin of the sinus. They may adhere to the lateral wall of the sinus before joining it. The length of the veins adherent to the sinus wall varies and is greatest with the most posterior veins, which may have as much as 8 cm of vein adherent to the sinus wall (17).

Enlarged venous spaces, called lacunae, are contained in the dura mater adjoining the superior sagittal sinus (Figs. 4.2, 4.3, and 4.8). The lacunae are largest and most constant in the parietal and posterior frontal regions. Smaller lacunae are found in the occipital and anterior frontal regions. In some cases, the separate lacunae are replaced by a single lacuna on each side of the sinus (17). The lacunae receive predominantly the drainage of the meningeal veins, which accompany the meningeal arteries in the dura mater. Some investigators have recorded that the lacunae do not receive the drainage of the cortical veins; however, we did find sites of communication between the cortical veins and the lacunae (17, 29). The cortical veins that empty into the superior sagittal sinus characteristically pass beneath rather than emptying directly into the lacunae to reach the sinus. The majority of the veins that pass beneath the lacunae open into the sinus separately from the lacunae, but some may share a common opening into the sinus with the lacunae. Very few cortical veins empty directly into the lacunae.

Arachnoid granulations, finger-like outpouchings of clumps of arachnoid cells, project into the floor and walls of the lacunae (9). The arachnoid granulations infrequently project into the superior sagittal sinus. In the granulations, the arachnoid cells rest against the endothelium lining the venous spaces. The increase in size of the lacunae with advancing age is thought to accompany the increase in size of the arachnoid granulations with age (9). O’Connell (17) emphasized the fact that, although a few granulations are found projecting into the venous sinuses, the vast majority project into the lacunae, which in the adult are carpeted with granulations. The arachnoid granulations are also found in proximity to the transverse, cavernous, superior petrosal, sphenoparietal, and straight sinuses (16).

The superior sagittal sinus is triangular in cross section and has right and left lateral angles at its junction with the dura mater covering the convexities and an inferior angle at its junction with the falx. The cortical veins may pass directly to the superior sagittal sinus, or they may join the meningeal sinuses, which empty into the superior sagittal sinus. The cortical veins passing directly to the superior sagittal sinus may join the lateral angles, lateral walls, or inferior angle of the sinus. Other cortical veins join the meningeal sinuses in the dura mater over the convexity 0.5 to 3.0 cm lateral to the superior sagittal sinus. These meningeal sinuses course medially to join the lateral angle of the superior sagittal sinus (Figs. 4.2 and 4.8). Several cortical veins may join a single meningeal sinus. Two or three meningeal sinuses may join to form a vestibule just before reaching the superior sagittal sinus. There is a tendency for the veins draining the lateral surface of the anterior frontal and posterior parietal regions to join the meningeal sinus in the dura mater lateral to the superior sagittal sinus. The veins from the posterior frontal and parietal region most commonly dip beneath the venous lacunae and pass directly to the superior sagittal sinus.

The veins from the medial surface of the hemisphere enter the inferior border of the sinus or turn laterally onto the superior margin of the hemisphere to join the veins from the lateral surface before entering the sinus. The segment of the superior sagittal sinus in the frontal region above the genu of the corpus callosum receives fewer bridging veins than any other area except the 4 to 6 cm proximal to the torcular herophili, where bridging veins infrequently enter the superior sagittal sinus.

FIGURE 4.7. Superior view of the cerebral hemispheres showing the veins from the lateral surface of the cerebrum entering the superior sagittal sinus. The veins entering the superior sagittal sinus are shown on the left and the average angles at which the veins enter the sinus are shown on the right. From anterior to posterior, the angles at which the veins join the sinus decrease. The average angles between the individual veins and the sinuses are as follows: frontopolar and anterior frontal veins, 110 degrees; middle frontal vein, 85 degrees; posterior frontal vein, 65 degrees; precentral vein, 50 degrees; central vein, 45 degrees; postcentral vein, 40 degrees; anterior parietal vein, 25 degrees; posterior parietal vein, 15 degrees; occipital vein, 10 degrees. Ant., anterior; Cent., central; Front., frontal; Mid., middle; Occip., occipital; Par., parietal; Post., posterior; Precent., precentral; V., vein. (From, Oka K, Rhoton AL Jr, Barry M, Rodriguez R: Microsurgical anatomy of the superficial veins of the cerebrum. Neurosurgery 17:711–748, 1985 [18].)

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FIGURE 4.8. A, the outer table of the cranium has been removed, while preserving the sutures, to expose the diploic veins (red arrows) coursing between the inner and outer table. B, the inner table has been removed to expose the meningeal sinuses coursing along the middle meningeal artery, while preserving the large posterior diploic vein in the bone. The upper end of the diploic vein joins the venous sinuses around the middle meningeal artery at the yellow arrow. C, superior view. The dura covering the cerebral hemispheres contains a plexus of small meningeal sinus veins that follow the branches of the meningeal arteries. The largest meningeal sinuses course along the anterior and posterior branches of the middle meningeal artery and extend up to the superior sagittal sinus and the region of the venous lacunae. D, the dura has been opened and the venous lacunae preserved. The veins from the posterior part of the hemisphere are directed forward. A., artery; Ant., anterior; Br., branch; Men., meningeal; Mid., middle; Occip., occipital; Post., posterior; Sag., sagittal; Squam., squamosal; Sup., superior; V., vein.

Inferior Sagittal Sinus

The inferior sagittal sinus courses in the inferior edge of the falx (Figs. 4.1 and 4.6). It originates above the anterior portion of the corpus callosum and enlarges as it courses posteriorly to join the straight sinus. It arises from the union of veins from the adjacent part of the falx, corpus callosum, and cingulate gyrus. The junction of the veins from the cingulate gyrus and corpus callosum with the sinus often forms an acute hook-like bend, with the apex directed forward. The largest tributaries of the inferior sagittal sinus are the anterior pericallosal veins. The superior sagittal sinus may communicate through a venous channel in the falx with the inferior sagittal sinus. This connection may infrequently be so large that the superior sagittal sinus drains predominantly into the inferior sagittal and straight sinuses (26).

Straight Sinus

The straight sinus originates behind the selenium of the corpus callosum at the union of the inferior sagittal sinus and the great vein (Figs. 4.1, 4.2, 4.4, and 4.5). It continues posteriorly and downward in the junction of the tentorium and falx. It may drain into either transverse sinus, but most commonly drains predominantly into the left transverse sinus.

Transverse Sinus

The right and left transverse sinuses originate at the torcular herophili and course laterally from the internal occipital protuberance in a shallow groove between the attachments of the tentorium to the inner surface of the occipital bone (Figs. 4.1, 4.4, 4.5, and 4.9). The transverse sinus exits the tentorial attachments to become the sigmoid sinus at the site just behind the petrous ridge, where the transverse and superior petrosal sinuses meet. Although the superior sagittal sinus may drain equally to the left and right transverse sinus or predominantly or wholly to either side, it is the right transverse sinus that is usually larger and receives the majority of the drainage from the superior sagittal sinus. The left transverse sinus is usually smaller and receives predominantly the drainage of the straight sinus. Thus, the right transverse sinus, right sigmoid sinus, and right jugular vein contain blood from the superficial parts of the brain, and the left transverse sinus, left sigmoid sinus, and left internal jugular vein contain blood mainly from the deep parts of the brain drained by the internal cerebral, basal, and great veins. The difference in symptoms caused by blockage of the venous drainage on one side or the other and the differences in Queckenstedt’s sign with compression of the jugular veins on either the left or right side have been explained by the differences in drainage on each side.

The cortical veins from the lateral surface of the temporal lobe may drain into the transverse sinus, but before entering it, they commonly pass medially below the hemisphere to join a short sinus in the tentorium, which courses within the tentorium for approximately 1 cm before draining into the terminal part of the transverse sinus (Figs. 4.1, 4.4, and 4.5). The cortical veins from the basal surface of the temporal and occipital lobes usually join the lateral tentorial sinus. The vein of Labbé commonly ends in the transverse sinus, but may curve around the inferior margin of the hemisphere to join the lateral tentorial sinus. The transverse sinus may communicate through emissary veins in the occipital bone with the extracranial veins.

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FIGURE 4.9. Posterior view of the cerebral and cerebellar hemispheres. A, the superior sagittal sinus is connected through the torcular herophili with the transverse sinuses. The right transverse sinus is slightly larger than the left. The veins arising along the posterior part of the hemisphere are directed forward and join the superior sagittal sinus well above the torcular herophili, leaving a void along the medial occipital lobe where there are no bridging veins emptying into the sinus. B, the tentorium has been elevated to show the veins from the cerebellum forming bridging veins that enter the sinuses in the lower margin of the tentorium. On the left side, a large vein (yellow arrow) passes from the superior surface of the cerebellar hemisphere to enter a tentorial sinus. On the right side, a large bridging vein from the suboccipital cerebellar surface (red arrow) turns forward on the superior surface and empties into a tentorial sinus in front of the torcular herophili. C, view below the tentorium. The vein of Galen empties into the straight sinus. A large superior vermian vein empties into the vein of Galen. The right basal and the right and left anterior calcarine veins are exposed. The left basal vein is hidden in front of the left superior cerebellar artery. D, the tentorium has been removed, while preserving the straight sinus and the tentorial edge. The vein of Galen and its tributaries are exposed in the quadrigeminal cistern. Both basal veins are exposed. Large anterior calcarine veins drain the calcarine sulcus and adjacent part of the atrium. The branches of the posterior cerebral artery course in the upper part of the quadrigeminal cistern and the branches of the superior cerebellar artery course in the lower part. Ant., anterior; Calc., calcarine; Cer., cerebral; Int., internal; Occip., occipital; Par., parietal; P.C.A., posterior cerebral artery; Post., posterior; Sag., sagittal; S.C.A., superior cerebellar artery; Sig., sigmoid; Str., straight; Sup., superior; Tent., tentorium, tentorial; Trans., Transv., transverse; V., vein; Verm., vermian.

Tentorial Sinuses

Each half of the tentorium has two constant but rarely symmetrical venous channels, the medial and lateral tentorial sinuses (Figs. 4.1, 4.4, and 4.5) (3). The medial tentorial sinuses are formed by the convergence of veins from the superior surface of the cerebellum, and the lateral tentorial sinuses are formed by the convergence of veins from the basal and lateral surfaces of the temporal and occipital lobes. The lateral tentorial sinuses arise within the lateral part of the tentorium and course laterally to drain into the terminal portion of the transverse sinus. The medial tentorial sinuses course medially to empty into the straight sinus or the junction of the straight and transverse sinuses.

Cavernous Sinus

The paired cavernous sinuses are situated on each side of the sella turcica and are connected across the midline by the anterior and posterior intercavernous sinuses, which course in the junction of the diaphragma sellae with the dura lining the sella (Fig. 4.1). Anteriorly, each cavernous sinus communicates with the sphenoparietal sinus and the ophthalmic veins. Its middle portion communicates through a lateral extension on the inner surface of the greater sphenoid wing with the pterygoid plexus via small veins that pass through the foramina spinosum and ovale. Posteriorly, the cavernous sinus opens directly into the basilar sinus, which sits on the clivus. It communicates through the superior petrosal sinus with the junction of the transverse and sigmoid sinuses and through the inferior petrosal sinus with the sigmoid sinus. Our studies of the cavernous sinus are reported in Chapter 9 in this issue, and other publications (23, 24).

Superior Petrosal Sinus

The superior petrosal sinus courses within the attachment of the tentorium to the petrous ridge (Figs. 4.1, 4.4, and 4.5). Its medial end connects with the posterior end of the cavernous sinus, and its lateral end joins the junction of the transverse and sigmoid sinuses. The bridging veins that join it usually arise from the cerebellum and brainstem, not the cerebrum. The sinus may course over, under, or around the posterior root of the trigeminal nerve. The superficial sylvian veins may empty into an infrequent tributary of the superior petrosal sinus called the sphenopetrosal sinus.

Sphenoparietal, Sphenobasal, and Sphenopetrosal Sinuses

The sphenoparietal sinus is the largest of the meningeal channels coursing with the meningeal arteries (Fig. 4.1). It accompanies the anterior branch of the middle meningeal artery above the level of the pterion. Below this level, it deviates from the artery and courses in the dura mater just below the sphenoid ridge to empty into the anterior part of the cavernous sinus. Its upper end communicates through the meningeal veins with the superior sagittal sinus. The sinus coursing along the sphenoid ridge may turn inferiorly to reach the floor of the middle cranial fossa rather than emptying into the anterior part of the cavernous sinus. From here, it courses posteriorly to empty into a lateral extension of the cavernous sinus on the greater sphenoid wing or joins the sphenoidal emissary veins, which pass through the floor of the middle fossa to reach the pterygoid plexus. It also may pass further posteriorly to join the superior petrosal or lateral sinuses. The variant in which the sinus exits the cranium by joining the sphenoidal emissary veins and the pterygoid plexus is referred to as the sphenobasal sinus, and the variant in which the sinus courses further posteriorly along the floor of the middle fossa and drains into the superior petrosal or lateral sinus is called the sphenopetrosal sinus. The superficial sylvian veins commonly empty into the sphenoparietal sinus. If the sphenoparietal sinus is absent or poorly developed, the sylvian veins may drain directly into the cavernous sinus or they may turn inferiorly around the anterior pole and inferior surface of the temporal lobe to empty into the sphenobasal or sphenopetrosal sinuses.

Anastomotic Veins

The largest veins on the lateral surface are the veins of Trolard and Labbé and the superficial sylvian veins (Figs. 4.10–4.12). The vein of Trolard is the largest anastomotic vein joining the superior sagittal sinus with the veins along the sylvian fissure. The vein of Labbé is the largest vein connecting the veins along the sylvian fissure with the transverse sinus (6, 7). The superficial sylvian vein courses along the surface of the sylvian fissure and drains predominantly into the dural sinuses along the sphenoid ridge. Although the veins of Trolard and Labbé and the superficial sylvian vein may be of nearly equal size, it is more common for one or two of them to predominate and the other to be small or absent. Usually, there is asymmetry between the right and left hemispheres in the size of these channels.

Vein of Trolard

The vein of Trolard, also called the superior anastomotic vein, is the largest anastomotic vein crossing the cortical surface of the frontal and parietal lobes between the superior sagittal sinus and the sylvian fissure (Figs. 4.10 and 4.11). In 15 of the 20 hemispheres examined in this study, the vein of Trolard was located at a site that would correspond to the precentral, central, or postcentral vein. It was most commonly located at the level of the postcentral vein. The most anterior vein of Trolard was situated at the level of the anterior frontal veins and connected the anterior part of the sagittal sinus with the anterior part of the superficial sylvian vein. The most posterior vein of Trolard was located at the level of the anterior parietal veins. The vein of Trolard usually joins the superior sagittal sinus as a single channel that is directed forward against the direction of flow as it joins the sinus. It is commonly joined by other veins immediately proximal to the sinus. Its lower end is usually a single channel that anastomoses with the veins along the sylvian fissure, but it may split on the lower part of the frontal and parietal convexity into multiple channels that join the superficial sylvian vein. There may be duplicate veins of Trolard, in which case two large veins of similar size cross the interval between the sylvian fissure and the superior sagittal sinus.

Vein of Labbé

The vein of Labbé, also called the inferior anastomotic vein, is the largest anastomotic channel that crosses the temporal lobe between the sylvian fissure and the transverse sinus (Figs. 4.5, 4.10, and 4.11). It usually arises from the middle portion of the sylvian fissure and is directed posteriorly and inferiorly toward the anterior part of the transverse sinus. It may cross the temporal lobe as far back as the posterior limit of the lobe or as far forward as the anterior third of the lateral surface. In the 20 hemispheres examined in this study, the vein of Labbé was located at the level of the middle temporal vein in 12, the posterior temporal vein in 6, and the anterior temporal vein in 2. There may be double veins of Labbé, in which case the posterior vein is usually larger (18).

Superficial Sylvian Vein

The superficial sylvian vein usually arises at the posterior end of the sylvian fissure and courses anteriorly and inferiorly along the lips of the fissure (Figs. 4.5 and 4.10–4.12). It may arise as two trunks, but these usually merge into a single channel before emptying into the venous sinuses along the sphenoid ridge. The superficial sylvian vein receives the frontosylvian, parietosylvian, and temporosylvian veins and commonly anastomoses with the veins of Trolard and Labbé. It penetrates the arachnoid covering the anterior end of the sylvian fissure and joins the sphenoparietal sinus as it courses just below the medial part of the sphenoid ridge, or it may pass directly to the cavernous sinus. It may also leave the sylvian fissure and course around the temporal pole to reach the dural sinuses in the floor of the middle fossa, which empty into the superior petrosal sinus or exit the intracranial cavity through the foramina in the sphenoid bone to reach the pterygoid plexus. The deep sylvian veins, which drain the insula and adjacent walls of the sylvian fissure, were reviewed in our studies on the deep venous system of the brain (20).

If the superficial sylvian vein is small or absent, the adjacent veins will take over its drainage area (Figs. 4.5 and 4.10–4.12). The veins arising on the upper lip of the sylvian fissure will ascend to join the veins that empty into the superior sagittal sinus, and those arising on the lower lip will be directed posteroinferiorly to join the veins entering the sinuses below the temporal lobe. If the central segment of the vein is absent, the anterior segment will join the sinuses along the sphenoid ridge and the posterior segment will join the anastomotic veins of Trolard and Labbé that drain into the superior sagittal and transverse sinuses.

FIGURE 4.10. Major anastomotic veins. A–D, different patterns. The dominant vein is darkly shaded. The vein of Trolard is the largest vein connecting the superficial sylvian vein with the superior sagittal sinus. The vein of Labbé is the largest vein connecting the superficial sylvian vein with the transverse sinus. The superficial sylvian vein drains the areas along the sylvian fissure and empties into the sinuses along the sphenoid ridge. A, all three anastomotic veins are present, but the veins of Labbé and Trolard are dominant. B, dominant superficial sylvian and vein of Trolard. C, dominant superficial sylvian vein. D, dominant vein of Labbé. Sup., superficial; V., vein.

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FIGURE 4.11. Comparison of the drainage pattern of different cerebral hemispheres. A, right lateral view. The veins draining this cerebral hemisphere are directed to the superior sagittal and transverse sinuses. The superficial sylvian vein is small. One small anastomotic vein of Trolard links the superior sagittal sinus and sylvian fissure. B, another right hemisphere. The superficial sylvian vein is large. There is minimal anastomosis between the superficial sylvian vein and the veins draining into the superior sagittal sinus, but there is a connection between the superficial sylvian vein and the vein of Labbé. In opening the sylvian fissure by the pterional approach, the drainage pattern for the whole hemisphere is not seen. Sacrificing the superficial sylvian vein shown in A would probably not affect the hemisphere, but sacrificing the large superficial sylvian vein shown in B could lead to venous drainage problems along the frontal and temporal lobes adjoining the sylvian fissure. C, left hemisphere. A superficial sylvian vein has a large connection with the vein of Labbé. In addition, two small or duplicate veins of Trolard connect the superior sagittal sinus and the sylvian vein. The posterior one joins the superficial sylvian vein near the junction with the vein of Labbé. D, left hemisphere. There are no significant connections between the veins in the sylvian fissure and the superior sagittal sinus, but there is a large anastomosis between the superficial sylvian vein and the vein of Labbé. E, right hemisphere. Duplicate veins of Trolard connect the superior sagittal sinus to the superficial sylvian veins; one crosses the frontal lobe and one crosses the parietal lobe. The superficial sylvian vein also has a large anastomosis with the vein of Labbé. F, right hemisphere. A single large vein of Trolard coursing in the region of the central sulcus connects the superficial sylvian vein and the superior sagittal sinus. This is no well-developed vein of Labbé, but a large vein from the posterior parietal and temporal areas (yellow arrow) empties into the superior sagittal sinus. Cent., central; Dup., duplicate; Fiss., fissure; Sup., superior; V., vein.

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FIGURE 4.12. A-D. Lateral view. Comparison of drainage pattern along the sylvian fissure on the right side (A and B) and left side (C and D) of the same brain. A, right lateral view. There is no significant superficial sylvian vein. The veins draining the frontal and parietal areas are relatively evenly dispersed over the frontal and parietal lobes and drain predominantly into the superior sagittal sinus. There are two, or duplicate, veins of nearly equal size that cross from the sylvian fissure to the transverse sinus and fit the description of a vein of Labbé. Central and posterior frontal veins of approximately the same size connect the sylvian fissure and superior sagittal sinus, and together constitute a duplicate vein of Trolard. The lower part of the central vein passes along the central sulcus. B, enlarged view of sylvian fissure. Duplicate veins of Labbé and Trolard drain much of the area along the sylvian fissure. C, left side. There is a large superficial sylvian vein that has minimal connections with the superior sagittal sinus; however, a significant part of the drainage from this area is directed through a vein of Labbé that crosses the midtemporal area. D, the sylvian fissure has been opened below the superficial sylvian vein that empties anteriorly into the sphenoparietal sinus coursing below the sphenoid ridge and posteriorly into a large vein of Labbé.

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FIGURE 4.12. E-H. E, right orbitozygomatic craniotomy. The temporalis muscle has been reflected downward, the bone flap elevated, and the dural incision (solid line) outlined. The inset shows the one-piece orbitozygomatic bone flap. F, the dura has been opened to expose a large superficial sylvian vein that empties into the dural sinuses along the sphenoid ridge. G, the sylvian fissure has been opened and the large superficial sylvian vein retracted to expose the internal carotid and middle cerebral artery. H, another orbitozygomatic exposure. In this case, the anterior segment of the superficial sylvian vein is absent and the veins draining the posterior part of the sylvian fissure empty into veins crossing the frontal and temporal lobes. A., artery; Car., carotid; Cent., central; CN, cranial nerve; Dup., duplicate; Fiss., fissure; Front., frontal; M., muscle; M.C.A., middle cerebral artery; Olf., olfactory; Post., posterior; Precent., precentral; Sup., superior; Temp., temporal, temporalis; Tr., tract; V., vein.

Cortical Veins

The superficial cortical veins are divided into three groups based on whether they drain the lateral, medial, or inferior surface of the hemisphere (Fig. 4.13). The cortical veins on the three surfaces are further subdivided on the basis of the lobe and cortical area that they drain. The largest group of cortical veins terminate by exiting the subarachnoid space to become bridging veins that cross the subdural space and empty into the venous sinuses in the dura mater. A smaller group of cortical veins terminate by joining the deep venous system of the brain (20).

Most of the individual veins outlined are formed by a single channel with multiple tributaries; however, two or more channels may infrequently pass from the individual cortical areas to the adjacent dural sinuses. There is a reciprocal relationship between the veins from adjacent areas so that, as the territory of one vein increases, the territory of the adjacent vein decreases. There is a similar reciprocal relationship between the major venous groups draining a surface or lobe.

The individual cortical veins from adjoining areas may join to form a single bridging vein before their termination in a dural sinus (Fig. 4.14). In addition, the veins draining the adjacent areas on the medial, lateral, and inferior surfaces may join along the margins of the hemisphere to form a single bridging vein before emptying into one of the sinuses. The ascending veins from the medial and lateral surfaces frequently join along the superior margin of the hemisphere before emptying into the superior sagittal sinus, and the descending veins from the lateral surface and the laterally directed veins from the inferior surface often join along the inferior margin of the hemisphere before draining into the sinuses along the cranial base. The individual veins from each of the lobes are considered next.

Frontal Lobe

The veins of the frontal lobe are divided into groups that drain the lateral, medial, and basal surfaces of the lobe (Figs. 4.1–4.4, 4.6, and 4.11–4.14). The lateral frontal veins are divided into an ascending group, which empties into the superior sagittal sinus, and a descending group, which courses toward the sylvian fissure and joins the superficial sylvian veins. The ascending veins are the frontopolar; anterior, middle, and posterior frontal; precentral; and central veins. The vein may join the veins from the adjoining parts of the basal and medial surfaces before emptying into the sinus. The descending group is composed of the frontosylvian veins. The area drained by the ascending group is larger than the area drained by the descending group.

The lateral frontal veins and the areas they drain are as follows: the frontopolar vein drains the anterior part of the inferior, middle, and superior frontal gyri; the anterior, middle, and posterior frontal veins drain the anterior, middle, and posterior part of the frontal convexity, in the area between the frontopolar and precentral veins; the precentral vein drains the lower part of the precentral gyrus, the opercular part of the inferior frontal gyrus, and the adjacent part of the inferior, middle, and superior frontal gyri; the central rolandic vein drains the precentral and postcentral gyri bordering the central sulcus; and the frontosylvian veins drain the inferior and adjoining part of the middle frontal gyri and the inferior part of the precentral gyrus.

The medial surface of the frontal lobe is divided by the curved cingulate sulcus into inner and outer zones. The medial frontal veins are divided into an ascending group, which drains into the superior sagittal sinus, and a descending group, which empties into the inferior sagittal sinus or into the veins that pass around the corpus callosum to drain into the anterior end of the basal vein. The ascending veins are the anteromedial, centromedial, and posteromedial frontal and paracentral veins. They drain the majority of the medial surface of the superior frontal gyrus and the adjoining part of the cingulate gyrus. They commonly curve over the superior margin of the hemisphere onto the upper part of the lateral surface, where they join the terminal end of the veins from the lateral surface before emptying into the superior sagittal sinus. The descending veins are the anterior pericallosal, paraterminal, and anterior cerebral veins.

The medial frontal veins and the areas they drain are as follows: the anteromedial frontal vein drains the cingulate and superior frontal gyri behind the frontal pole; the centromedial frontal vein drains the medial surface of the superior frontal gyrus and the adjacent part of the cingulate gyrus in front of the genu of the corpus callosum; the posteromedial frontal vein drains the superior frontal and cingulate gyri situated above the genu of the corpus callosum; the paracentral vein drains the cingulate gyrus above the body of the corpus callosum and adjacent paracentral lobule; the anterior pericallosal veins—paired veins—drain the genu and rostrum of the corpus callosum and adjacent part of the cingulate gyri; the anterior cerebral vein drains the area below the rostrum of the corpus callosum near the upper margin of the optic chiasm; and the paraterminal vein drains the paraterminal and paraolfactory gyri in the area below the rostrum of the corpus callosum.

The inferior frontal veins, draining the orbital surface of the frontal lobe, are divided into an anterior group, which courses toward the frontal pole and empties into the superior sagittal sinus, and a posterior group, which drains backward to join the veins at the medial part of the sylvian fissure, that converge on the anterior perforated substance to form the basal vein. The anterior group is composed of the anterior orbitofrontal and frontopolar veins. The posterior group is composed of the olfactory and the posterior orbitofrontal veins.

The inferior frontal veins and the areas they drain are as follows: the anterior orbitofrontal vein drains the anterior part of the gyrus rectus and the anteromedial part of the orbital gyri; the posterior orbitofrontal veins drain the posterior portion of the orbital surface of the frontal lobe; and the olfactory vein drains the olfactory sulcus and the adjacent part of the gyrus rectus and medial orbital gyri.

Figure 4.13. Territory and direction of drainage of the cortical veins. A, C, and E, territory of each cortical vein. B, D, and F, direction of drainage of veins on each lobe. A and B, lateral surface. C and D, medial surface. E and F, inferior surface. A, C, and E, territory drained by each cortical vein is shaded in a color specific to its lobe: frontal veins (shades of blue), parietal veins (shades of yellow), temporal veins (shades of green), and occipital veins (shades of purple). A, territory of veins on the lateral surface. The lateral surface of the frontal lobe (blue) is drained by the frontopolar, anterior frontal, middle frontal, posterior frontal, precentral, central, and the frontosylvian veins. The lateral surface of the parietal lobe (yellow) is drained by the central, postcentral, anterior parietal, posterior parietal, and parietosylvian veins. The lateral surface of the occipital lobe (purple) is drained by the occipital veins. The lateral surface of the temporal lobe (green) is drained by the anterior temporal, middle temporal, posterior temporal, and temporosylvian veins. B, direction of drainage on the lateral surface. The veins draining the lateral surface of the frontal lobe are shown in two shades of blue: a lighter shade for the ascending veins, which drain into the superior sagittal sinus, and a darker shade for the descending veins, which drain into the superficial sylvian vein. The ascending frontal veins are the frontopolar; anterior frontal, middle frontal, and posterior frontal veins; and precentral and central veins. The descending lateral frontal veins are the frontosylvian veins. The veins draining the lateral surface of the parietal lobe are shown in two shades of red: a light shade for the ascending veins, which drain into the superior sagittal sinus, and a darker shade for the descending veins, which drain into the superficial sylvian vein. The ascending lateral parietal veins are the central, postcentral, anterior parietal, and posterior parietal veins. The vein of Trolard corresponds to a large postcentral vein. The descending lateral parietal veins are the parietosylvian veins. The veins draining the lateral surface of the occipital lobe are shown in purple: they are predominantly ascending veins called occipital veins, which ascend to join the superior sagittal sinus. A few occipital veins may descend to join the transverse sinus or tentorial sinus. The veins draining the lateral surface of the temporal lobe are shown in two shades of green: a light shade for the veins that ascend to empty into the superficial sylvian vein and a darker shade for the veins that descend to reach the sinuses in the tentorium. The ascending lateral temporal veins are the temporosylvian veins. The descending lateral temporal veins are the anterior temporal, middle temporal, and posterior temporal veins. C, territory of veins on the medial surface. The medial surface of the frontal lobe (blue) is drained by the paraterminal, anteromedial frontal, centromedial frontal, posteromedial frontal, anterior pericallosal, and paracentral veins. The medial surface of the parietal lobe (yellow) is drained by the paracentral, anteromedial parietal, posteromedial parietal, and posterior pericallosal veins. The medial surface of the occipital lobe (purple) is drained by the anterior calcarine and posterior calcarine veins. D, direction of drainage on the medial surface. The veins draining the medial surface of the frontal lobe are shown in two shades of blue: a lighter shade for the ascending veins, which pass to the superior sagittal sinus, and a darker shade for the descending veins, which drain into the inferior sagittal sinus and anterior cerebral and basal veins. The ascending medial frontal veins are the anteromedial frontal, centromedial frontal, posteromedial frontal, and paracentral veins. The descending medial frontal veins are the paraterminal and anterior pericallosal veins. The veins on the medial surface of the parietal lobe are shown as two shades of red: a lighter shade for the ascending veins, which drain into the superior sagittal sinus, and a darker shade for the descending veins, which drain into the vein of Galen and its tributaries. The ascending medial parietal veins are the paracentral, anteromedial parietal, and posteromedial parietal veins. The descending medial parietal veins are the posterior pericallosal veins. The veins on the medial surface of the occipital lobe are shown in two shades of purple: a lighter color for the ascending veins draining into the superior sagittal sinus and a darker shade for the veins draining into the vein of Galen and its tributaries. The ascending medial occipital vein is the posterior calcarine vein, and the vein draining into the deep venous system is the anterior calcarine vein. E, territory of veins on the inferior surface. The inferior surface of the frontal lobe (blue) is drained by the frontopolar, anterior fronto-orbital, posterior fronto-orbital, olfactory, and paraterminal veins. The inferior surface of the temporal lobe (green) is drained by the anterior temporobasal, middle temporobasal, posterior temporobasal, anterior hippocampal, uncal, medial temporal, and temporosylvian veins. The interior surface of the occipital lobe (purple) is drained by the occipitobasal vein. F, direction of drainage on the inferior surface. The veins on the inferior surface of the frontal lobe are shown in two shades of blue: a lighter shade for the anterior veins, which drain into the superior sagittal sinus, and a darker color for the posterior veins, which empty into the anterior end of the basal vein. The anterior group of the inferior frontal veins are the anterior fronto-orbital veins. The posterior group of inferior frontal veins are the posterior fronto-orbital and olfactory veins. The veins on the inferior surface of the temporal lobe are shown in two shades of green: a darker shade for the veins that are directed laterally to empty into the sinuses in the tentorium and a lighter shade for the veins that are directed medially to drain into the basal vein. The laterally directed inferior temporal veins are the anterior temporobasal, middle temporobasal, and posterior temporobasal veins; the medially directed veins are the uncal, anterior hippocampal, and medial temporal veins. The veins on the inferior surface of the occipital lobe are shown as one shade of purple, because there is only one group, the occipitobasal veins, that empty into the sinuses in the tentorium. The internal cerebral vein joins the vein of Galen. Ant., anterior; Calc., calcarine; Cent., central; Front., frontal; Front.Orb., fronto-orbital; Hippo., hippocampal; Med., medial; Mid., middle; Occip., occipital; Olf., olfactory; Orb., orbital; Par., parietal; Paracent., paracentral; Paraterm., paraterminal; Pericall., pericallosal; Post., posterior; Postcent., postcentral; Post.Med., posteromedial; Precent., precentral; Temp., temporal; V., vein.

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FIGURE 4.14. A, cerebrum with the coronal and sagittal sutures preserved, superior view. There is commonly an area devoid of bridging veins entering the superior sagittal sinus just in front of the coronal suture, as shown, that would be a suitable site for a transcallosal approach. The author places the flap for a transcallosal approach exposure one-third behind and two-thirds in front of the coronal suture. B, lateral view, right hemisphere. The area in front of the coronal sutures is devoid of bridging veins emptying into the superior sagittal sinus. C and D, anterior and left anterolateral views of another cerebrum. C, anterior view. On the left side, a large bridging vein (yellow arrow), into which the anterior, middle, and posterior frontal veins empty, drains almost all of the left frontal lobe. On the right side, two large bridging veins (red and white arrows) drain most of the frontal lobe. D, anterolateral view of the left hemisphere. A large part of the left frontal lobe is drained by a single large bridging vein (yellow arrow). In the limited exposures used for surgical approaches, it is difficult to know how significant the anastomotic channels are. Sacrificing the large bridging vein on the left frontal lobe is more likely to produce a disturbance of venous drainage than sacrificing the smaller frontal bridging veins on the right side. Ant., anterior; Cent., central; Front., frontal; Mid., middle; Par., parietal; Post., posterior; Precent., precentral; Sag., sagittal; V., vein.

Parietal Lobe

The veins of the parietal lobe are divided on the basis of whether they drain the lateral or medial surfaces of the lobe (Fig. 4.1–4.3, 4.6, and 4.13). The veins draining the lateral surface are divided into an ascending group, which empties into the superior sagittal sinus, and a descending group, which drains into the veins along the sylvian fissure. The ascending veins are the central and postcentral veins and the anterior and posterior parietal veins. The descending group is formed by the parietosylvian veins.

The veins and the areas they drain are as follows: the postcentral vein drains the anterior part of the supramarginal gyrus and superior parietal lobule and the posterior part of the postcentral gyrus; the anterior parietal vein drains the supramarginal and angular gyri; the posterior parietal vein drains the posterior part of the inferior parietal lobule and the adjacent part of the occipital lobe; and the parietosylvian veins drain the postcentral gyrus and the inferior parietal lobule.

The medial parietal veins are divided into an ascending group, which drains into the superior sagittal sinus, and a descending group, which courses around the splenium of the corpus callosum to empty into the vein of Galen or its tributaries. The ascending veins are the paracentral and the anteromedial and posteromedial parietal veins. The descending veins are the posterior pericallosal veins. The ascending veins from the medial and lateral surfaces commonly join along the superior margin of the hemisphere before emptying into the superior sagittal sinus. The paracentral veins, which drain the adjacent parts of the frontal and parietal lobes, are described with the medial frontal veins.

The medial parietal veins and the areas they drain are as follows: the anteromedial parietal vein drains the upper edge of the cingulate gyrus and the anterior part of the precuneus; the posteromedial parietal vein drains the posterior part of the precuneus and the adjacent part of the occipital lobe; and the posterior pericallosal veins—paired veins—drain the posterior part of the corpus callosum, cingulate gyrus, and the precuneus.

Temporal Lobe

The veins of the temporal lobe are divided into a lateral group, which drains the convexity, and an inferior group, which drains the basal surface of the lobe (Figs. 4.1, 4.4, 4.5, and 4.11–4.13). The lateral temporal veins are divided into an ascending group, which courses toward the sylvian fissure, and a descending group, which empties into the venous sinuses below the temporal lobe. The ascending group is formed by the temporosylvian veins. The descending group is formed by the anterior, middle, and posterior temporal veins.

The lateral group of veins and the areas they drain are as follows: the anterior temporal vein drains the anterior third of the lateral surface, with the exception of the superior temporal gyrus; the middle temporal vein drains the midportion of the temporal convexity; the posterior temporal vein drains the posterior third of the temporal convexity and occasionally the angular gyrus and the anterior part of the occipital lobe; and the temporosylvian veins drain the superior temporal gyrus from the temporal pole to the posterior end of the sylvian fissure.

The inferior temporal veins are divided into a lateral group, which drains into the sinuses in the anterolateral part of the tentorium, and a medial group, which empties into the basal vein as it courses along the medial edge of the temporal lobe. The lateral group is composed of the anterior, middle, and posterior temporobasal veins. The temporobasal veins seem to radiate from the preoccipital notch across the inferior surface of the temporal lobe. The medial group is formed by the uncal, anterior hippocampal, and medial temporal veins. The part of the basal surface adjoining the temporal pole is commonly drained by the temporosylvian veins.

The inferior temporal veins and the areas they drain are as follows: the anterior temporobasal vein drains the anterior third of the inferior temporal and occipitotemporal gyri and the adjacent part of the parahippocampal gyrus; the middle temporobasal vein drains the middle third of the inferior surface of the lobe; the posterior temporobasal vein drains the basal surface of the temporal lobe and the anterior part of the occipital lobe; the uncal veins drain the uncus and the adjacent part of the parahippocampal gyrus; the anterior hippocampal vein drains the posterior portion of the uncus and the adjacent part of the parahippocampal gyrus; and the medial temporal veins drain the parahippocampal gyri bordering the basal cisterns beside the upper midbrain.

Occipital Lobe

The veins draining the occipital lobe are divided into groups that drain the lateral, medial, or inferior surfaces of the lobe (Figs. 4.1, 4.2, 4.5, and 4.13). The veins draining the posterior part of the temporal and parietal lobes may drain the anterior part of the occipital lobe. The fact that the lateral occipital veins are directed forward rather than backward means that no large veins enter the superior sagittal sinus for a distance of 4 to 5 cm proximal to the torcular herophili, or directly medial to the posterior part of the occipital lobe. The medial surface of the occipital lobe is drained by the anterior and posterior calcarine veins. The anterior calcarine vein (also referred to as the internal occipital vein) drains the anterior portion of the cuneus and lingula, and the posterior calcarine vein drains the area bordering the posterior part of the calcarine fissure.

The inferior surface of the occipital lobe is drained by the occipitobasal vein. The occipitobasal vein arises from tributaries that drain the inferolateral part of the lingula and the adjacent part of the occipitotemporal and inferior temporal gyri. It courses anterolaterally toward the preoccipital notch and frequently joins the posterior temporobasal vein before emptying into the lateral tentorial sinus. This vein may infrequently course anteromedial to join the basal vein.

Meningeal Veins

The small venous channels that drain the dura mater covering the cerebrum are called the meningeal veins (Fig. 4.8). They are actually small sinuses that usually accompany the meningeal arteries. The meningeal veins accompanying the meningeal arteries course between the arteries and the overlying bone. The fact that the artery presses into the veins gives them the appearance of parallel channels on each side of their respective arteries. The largest meningeal veins accompany the middle meningeal artery. The meningeal veins drain into the large dural sinuses along the cranial base at their lower margin and into the venous lacunae and superior sagittal sinus at their upper margin. The veins accompanying the anterior branch of the middle meningeal artery join the sphenoparietal or cavernous sinus or the sphenoidal emissary veins, and those accompanying the posterior branch of the middle meningeal artery join the lateral sinus. The meningeal veins may course through a superficial tunnel on the inner surface of the bone so that they have both an intradiploic and an intradural course. The meningeal veins receive diploid veins from the calvarium.

The Deep Veins

The deep venous system collects into channels that course through the walls of the ventricles and basal cisterns and converge on the internal cerebral, basal, and great veins (Figs. 4.15–4.17). During operations on the lateral ventricles, the deep veins more commonly provide orienting landmarks than the arteries because the arteries in the ventricular walls are small and poorly seen and the veins are larger and are easily visible through the ependyma. These venous landmarks are especially helpful in the presence of hydrocephalus, in which the normal angles between the neural structures disappear. The deep veins in the basal cisterns pose a major obstacle in operative approaches to deep-seated tumors, especially in the pineal region where multiple veins converge on the vein of Galen. On cerebral angiograms, these veins may provide a more accurate estimation of the site and size of a lesion than the arteries, because they are more closely adherent to the pial and ependymal surfaces of the brain than the arteries.

The deep venous system of the brain consists of the internal cerebral, basal, and great veins and their tributaries. These veins drain the deep white and gray matter surrounding the lateral and third ventricles and the basal cisterns. The deep veins are divided into a ventricular group, composed of the veins draining the walls of the lateral ventricles, and a cisternal group, which includes the veins draining the walls of the basal cisterns. The internal cerebral vein is discussed with the ventricular group, because it is predominantly related to the ventricles. The basal and great veins, although they receive some ventricular veins, are discussed with the cisternal group, because they course through the basal cisterns. The choroidal veins are included with the ventricular veins, because they arise on the choroid plexus in the ventricles. The thalamic veins are discussed in both the ventricular and the cisternal groups, because some course on the ventricular surface and others course in the basal cisterns. There are frequent anastomosis with veins from adjacent areas and it is common for veins from adjacent areas to form common stems before terminating in the larger draining veins.

FIGURE 4.15. Schematic drawing of the ventricular veins. Lateral (top), anterior (middle), and superior (lower) views. The ventricular veins are divided into a medial (orange) and a lateral (green) group. The ventricular veins drain into the internal cerebral, basal, and great veins. The lateral group consists of the anterior caudate vein in the frontal horn; the thalamostriate in the frontal horn; the thalamostriate, posterior caudate, and thalamocaudate veins in the body; the lateral atrial vein in the atrium; and the inferior ventricular vein and amygdalar veins in the temporal horn. The medial group is formed by the anterior septal vein in the frontal horn, the posterior septal veins in the body, the medial atrial vein in the atrium, and the transverse hippocampal veins in the temporal horn. The transverse hippocampal veins drain into the anterior and posterior longitudinal hippocampal veins. The superior choroidal veins drain into the thalamostriate and internal cerebral veins, and the inferior choroidal vein drains into the inferior ventricular vein. The vein of Galen drains into the straight sinus. The anterior and deep middle cerebral veins join to form the basal vein. Amygd., amygdala; Ant., anterior; Atr., atrial; Caud., caudate; Cer., cerebral; Chor., choroidal; Hippo., hippocampal; Inf., inferior; Int., internal; Lat., lateral; Long., longus; Med., medial; Mid., middle; Post., posterior; Sept., septal; Str., straight; Sup., superior; Thal.Caud., thalamocaudate; Thal.Str., thalamostriate; Trans., transverse; V., vein; Vent., ventricular. (From, Ono M, Rhoton AL Jr, Peace D, Rodriguez R: Microsurgical anatomy of the deep venous system of the brain. Neurosurgery 15:621–657, 1984 [20].)

FIGURE 4.16. Ventricular veins. A, anterior view (along the arrow in the inset) into the frontal horn and body of the lateral ventricle. The frontal horn is located anterior to the foramen of Monro and has the septum pellucidum in the medial wall, the genu and body of the corpus callosum in the roof, the caudate nucleus in the lateral wall, the genu of the corpus callosum in the anterior wall, and the rostrum of the corpus callosum in the floor. The body of the lateral ventricle has the thalamus in its floor, the caudate nucleus in the lateral wall, the body of the fornix and septum pellucidum in the medial wall, and the corpus callosum in the roof. The choroid plexus is attached along the choroidal fissure, the cleft between the fornix and thalamus. The anterior septal veins cross the roof and medial wall of the frontal horn and pass posteriorly toward the foramen of Monro, where they join the anterior end of the internal cerebral veins. The anterior caudate veins cross the lateral wall of the frontal horn and join the thalamostriate vein, which passes through the foramen of Monro. The superior choroidal vein courses on the choroid plexus in the body. The posterior septal veins cross the roof and medial wall of the body and pass through the margin of the choroidal fissure. The posterior caudate veins cross the lateral wall of the body and join the thalamostriate vein, which courses along the striothalamic sulcus. Anterior and superior superficial thalamic veins cross the surface of the thalamus. The anterior thalamic vein drains the nuclei in the anterosuperior part of the thalamus. B, anterosuperior view (along the arrow in the inset) into the body, atrium, and occipital horn of the lateral ventricle. The calcar avis and bulb of the corpus callosum form the medial wall of the atrium and occipital horn. The floor of the atrium is formed by the collateral trigone. The roof and posterior part of the lateral walls are formed by the tapetum of the corpus callosum. The caudate nucleus is in the anterior part of the lateral wall of the atrium. The medial and lateral atrial veins pass forward on the medial and lateral walls of the atrium toward the choroidal fissure. A thalamocaudate vein crosses the lateral wall posterior to the thalamostriate vein. The superior choroidal vein courses toward the foramen of Monro. C, posterior view (along the arrow in the inset) into the atrium and temporal horn. The inferior choroidal vein courses on the choroid plexus in the temporal horn. The lateral atrial veins arise on the lateral wall and cross the tail of the caudate nucleus and the pulvinar to pass through the choroidal fissure. The medial atrial veins pass forward and penetrate the crus of the fornix near the choroidal fissure to reach the quadrigeminal cistern. Some of the medial atrial veins also drain the roof and floor. Transverse hippocampal veins cross the floor of the atrium and temporal horn. Posterior superficial thalamic veins cross the atrial surface of the thalamus. D, anterior view (along the arrow in the inset) into the temporal horn. The floor of the temporal horn is formed by the collateral eminence and the hippocampal formation. The roof and lateral wall are formed, from medial to lateral, by the thalamus, the tail of the caudate nucleus, and the tapetum of the corpus callosum. The medial wall is little more than the cleft between the inferior surface of the thalamus and the fimbria. The amygdaloid nucleus bulges into the anteromedial part of the temporal horn. The pes hippocampus, the bulbous digitated anterior end of the hippocampal formation, is in the anterior part of the floor. The fimbria of the fornix arises on the surface of the hippocampal formation and passes posteriorly to become the crus of the fornix. The choroid plexus is attached along the choroidal fissure. The inferior ventricular vein drains the roof of the temporal horn and receives the amygdalar vein from the ventricular surface of the amygdaloid nucleus. The inferior choroidal vein joins the inferior ventricular vein. The transverse hippocampal veins draining the floor of the temporal horn pass medially through the choroidal fissure to enter the basal vein or its tributaries. Amygd., amygdaloid; Ant., anterior; Atr., atrial; Call., callosum; Caud., caudate; Chor., choroid, choroidal; Coll., collateral; Corp., corpus; Fiss., fissure; For., foramen; Front., frontal; Hippo., hippocampal; Inf., inferior; Lat., lateral; Med., medial; Nucl., nucleus; Occip., occipital; Pell., pellucidum; Plex., plexus; Post., posterior; Sept., septal, septum; Str., straight; Sulc., sulcus; Sup., superior; Superf., superficial; Temp., temporal; Thal., thalamic; Thal.Caud., thalamocaudate; Thal.Str., thalamostriate; Trans., transverse; Trig., trigone; V., vein; Vent., ventricle. (From, Ono M, Rhoton AL Jr, Peace D, Rodriguez R: Microsurgical anatomy of the deep venous system of the brain. Neurosurgery 15:621–657, 1984 [20].)

FIGURE 4.17. Cisternal veins. A, anterolateral view. The inset shows the direction of view. The frontal and temporal lobes have been retracted away from the floor of the anterior and middle cranial fossae. The veins converging on the anterior end of the basal vein below the anterior perforated substance are the deep middle cerebral veins from the sylvian fissure; the olfactory vein, which drains posteriorly along the olfactory tract near the gyrus rectus; the orbitofrontal veins, which drain the orbital gyri; the inferior striate veins, which exit the anterior perforated substance; and the anterior cerebral veins, which are joined above the optic chiasm by the anterior communicating vein. The peduncular vein passes around the cerebral peduncle above the oculomotor nerve and joins the median anterior pontomesencephalic vein in the midline and the basal vein laterally. The infundibulum passes inferiorly behind the anterior clinoid process, optic nerve, and internal carotid artery. The lateral anterior pontomesencephalic vein joins the vein of the pontomesencephalic sulcus below and the basal vein above. The inferior thalamic veins arise behind and the premamillary veins arise in front of the mamillary bodies. The inferior ventricular vein exits the temporal horn above the parahippocampal gyrus and enters the basal vein. An uncal vein passes medially from the uncus. The trochlear nerve courses near the tentorial edge. B, lateral view, right side. The temporal lobe has been elevated, as shown in the inset. The tentorium extends along the side of the brainstem. The basal vein passes around the brainstem and joins the vein of Galen. The tributaries of the basal veins lateral to the brainstem include the lateral mesencephalic vein, which courses in the lateral mesencephalic sulcus; the inferior ventricular vein, which drains the roof of the temporal horn; the anterior hippocampal vein, which courses along the sulcus between the uncus and the parahippocampal gyrus; the anterior longitudinal hippocampal vein, which courses along the dentate gyrus; and the medial temporal veins from the inferomedial surface of the temporal lobe. In the pineal region, the basal vein receives the lateral atrial vein from the lateral wall of the atrium. The internal cerebral veins pass above the pineal body. The superior vermian and superior hemispheric veins from the cerebellum and the vein of the cerebellomesencephalic fissure from the fissure between the midbrain and cerebellum ascend to join the vein of Galen. Tectal veins drain the colliculi. A transverse pontine vein crosses the pons. C, posterior view. The inset shows the direction of view. The occipital and parietal lobes have been retracted to expose the termination of the internal cerebral and basal veins in the vein of Galen. The internal occipital and posterior pericallosal veins join the internal cerebral vein. The posterior longitudinal hippocampal vein passes along the dentate gyrus and joins the medial atrial vein. The lateral mesencephalic, posterior thalamic, and inferior ventricular veins join the basal vein. Tectal veins pass from the superior and inferior colliculi. The medial and lateral geniculate bodies are below the pulvinar. The inferior sagittal sinus and the vein of Galen join the straight sinus. D, right anterolateral view with the anterior portion of the right cerebral hemisphere removed to expose the upper brainstem and the third ventricle in the midline. The brainstem was sectioned at the level of the cerebral peduncle. The anterior cerebral veins join the deep middle cerebral vein to form the basal vein. The basal vein encircles the brainstem and along its course receives the peduncular, inferior ventricular, anterior hippocampal, anterior longitudinal hippocampal, posterior thalamic, lateral atrial, lateral anterior pontomesencephalic, and lateral mesencephalic veins. The superior vermian vein receives the superior hemispheric and tectal veins and the vein of the cerebellomesencephalic fissure. The paraterminal and anterior pericallosal veins join the anterior cerebral vein. The internal cerebral vein courses in the velum interpositum in the roof of the third ventricle. The collateral eminence sits above the collateral sulcus in the floor of the temporal horn. Septal veins cross the septum pellucidum. The choroid plexus passes through the foramen of Monro to reach the roof of the third ventricle. A., artery; Ant., anterior; Atr., atrial; Call., callosum; Car., carotid; Cer., cerebral; Cer.Mes., cerebellomesencephalic; Coll., collateral; Comm., communicating; Corp., corpus; Fiss., fissure; For., foramen; Front., frontal; Front.Orb., orbitofrontal; Gen., geniculate; Gyr., gyrus; He., hemispheric; Hippo., hippocampal, hippocampus; Inf., inferior; Infund., infundibulum; Int., internal; Interpos., interpositum; Lat., lateral; Long., longus; Med., medial; Mes., mesencephalic; Mid., middle; N., nerve; Occip., occipital; Olf., olfactory; Orb., orbital; Par., parietal; Parahippo., parahippocampal; Paraterm., paraterminal; Ped., peduncle, peduncular; Pell., pellucidum; Perf., perforated; Pericall., pericallosal; Pon., pontine; Pon.Mes., pontomesencephalic; Premam., premamillary; Sag., sagittal; Sept., septal, septum; Str., straight; Subst., substance; Sulc., sulcus; Sup., superior; Temp., temporal; Tent., tentorial, tentorium; Thal., thalamic; Tr., tract; Trans., transverse; V., vein; Ve., vermian; Vel., velum; Vent., ventricle, ventricular. (From, Ono M, Rhoton AL Jr, Peace D, Rodriguez R: Microsurgical anatomy of the deep venous system of the brain. Neurosurgery 15:621–657, 1984 [20].)

Ventricular Group

Neural Relationships

Each lateral ventricle is a C-shaped cavity that wraps around the thalamus and is situated deep within the cerebrum (Figs. 4.15 and 4.16). Each ventricle has five parts: the frontal, temporal, and occipital horns and the body and atrium. Each of these five parts has medial and lateral walls, a roof, and a floor. In addition, the frontal and temporal horns and the atrium have anterior walls. These walls are formed predominantly by the thalamus, septum pellucidum, deep cerebral white matter, corpus callosum, and two C-shaped structures, the caudate nucleus and fornix, that wrap around the thalamus. These neural relationships of the ventricles are reviewed in detail in Chapter 5.

Choroid Plexus and Choroidal Fissure

The choroid plexus in the lateral ventricle has a C-shaped configuration that parallels the fornix (Figs. 4.15, 4.16, and 4.18–4.20) (8). It is attached along the choroidal fissure, a narrow cleft between the fornix and the thalamus, in the medial part of the body, atrium, and temporal horn. The choroid plexus extends through the foramen of Monro into the roof of the third ventricle. In the atrium, the choroid plexus has a prominent triangular tuft called the glomus. The edges of the thalamus and fornix bordering this fissure have small ridges, the teniae, along which the tela choroidea, the membrane in which the choroid plexus arises, is attached. The choroidal fissure extends from the foramen of Monro along the medial wall of the body, atrium, and temporal horn to its inferior termination, the inferior choroidal point, located just behind the uncus and hippocampal head. The veins coursing in the walls of the lateral ventricles exit the ventricles by passing, in a subependymal location, through the margin of this fissure to reach the internal cerebral, basal, or great veins.

Velum Interpositum

The velum interpositum, on which many of the ventricular veins converge to reach the internal cerebral veins, is located in the roof of the third ventricle below the fornix and between the superomedial surfaces of the thalami (Figs. 4.17 and 4.18). The velum interpositum is usually a closed space. It is widest posteriorly where it extends from the lower margin of the splenium to the upper margin of the pineal and tapers to a narrow apex just behind the foramen of Monro. It may infrequently have an opening situated between the splenium and the pineal body that communicates with the quadrigeminal cistern to form the cisterna velum interpositum. The upper and lower walls of the velum interpositum are formed by the two membranous layers of tela choroidea in the roof of the third ventricle. The upper wall is formed by the layer that is attached to the lower surface of the fornix and the hippocampal commissure. The lower wall is attached to the striae medullaris thalami, habenular commissure, and pineal. The internal cerebral veins arise in the anterior part of the velum interpositum, just behind the foramen of Monro, and they exit the velum interpositum above the pineal body to enter the quadrigeminal cistern and join the great vein.

Ventricular Veins

The ventricular veins arise from tributaries that drain the basal ganglia, thalamus, internal capsule, corpus callosum, septum pellucidum, fornix, and deep white matter (Figs. 4.15, 4.16, and 4.18–4.20). These tributaries converge on the lateral edge of the lateral ventricles, where they split into medial and lateral groups based on whether they course through the thalamic or the forniceal side of the choroidal fissure. The lateral group passes through the thalamic or inner side of the fissure, and the medial group passes through the outer or forniceal circumference of the fissure. Both groups course along the walls of the ventricle in a subependymal location toward the choroidal fissure. The lateral group drains the lateral wall and passes along the inner or thalamic side of the ventricle. This group drains the lateral wall and the floor of the frontal horn, body, atrium, and occipital horn, and the roof of the temporal horn. The veins in this group pass, in a subependymal location, through the thalamic side of the choroidal fissure to terminate in the internal cerebral, basal, and great vein. The medial group drains the medial wall plus the ventricular wall opposite the thalamus. This group drains the medial wall and the roof of the frontal horn, body, atrium, and occipital horn and the floor of the temporal horn. After reaching the medial part of the ventricle near the choroidal fissure, the veins in the medial group exit the ventricle by piercing the fornix to join the internal cerebral, basal, or great vein.

The veins of the medial and lateral groups frequently join near the choroidal fissure to form a common stem before terminating in the large veins in the velum interpositum and basal cisterns. In general, the veins draining the frontal horn and the body of the lateral ventricle drain into the internal cerebral vein as it courses through the velum interpositum, those draining the temporal horn drain into the segment of the basal vein coursing through the ambient and crural cisterns, and the veins from the atrium drain into the segments of the basal, internal cerebral, and great veins coursing through the quadrigeminal cistern. The internal cerebral veins, as they course through the velum interpositum, receive tributaries from the thalamus, the fornix, and the walls of the third ventricle, in addition to tributaries from the walls of the lateral ventricle.

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FIGURE 4.18. Internal cerebral veins in the roof of the third ventricle. A, superior view of the frontal horn and body. The thalamostriate and superior choroidal veins converge on the posterior edge of the foramen of Monro. The superior and anterior margin of the foramen of Monro is formed by the fornix. B, the fornix has been folded backward to expose the tela choroidea and the internal cerebral veins in the roof of the third ventricle. A thin layer of ependyma extends above and partially hides the thalamostriate veins coursing along the sulcus between the thalamus and caudate nucleus. The anterior caudate and anterior septal veins cross the lateral and medial wall of the frontal horn. The posterior caudate veins cross the lateral wall of the body of the ventricle. Only a small part of the upper layer of tela located between the fornix and internal cerebral veins remains. C, the internal cerebral veins have been separated to expose the branches of the medial posterior choroidal artery and the lower layer of tela choroidea that forms the floor of the velum interpositum in the roof of the third ventricle. The lower wall of the velum interpositum, in which the internal cerebral veins and medial posterior choroidal arteries course, is formed by the layer of tela attached along the medial side of the thalamus to the striae medullaris thalami. D, the lower layer of tela has been opened and the internal cerebral veins and the medial posterior choroidal arteries have been retracted to expose the posterior commissure, pineal gland, and massa intermedia. E, another hemisphere. The upper part of the hemisphere has been removed to expose the frontal horn, body and atrium of the lateral ventricle. The choroid plexus is attached along the choroidal fissure. The anterior and posterior caudate veins cross the lateral wall and the anterior and posterior septal veins cross the medial wall of the frontal horn and body of the lateral ventricle. The superior choroidal veins course along the choroid plexus. The thalamostriate veins pass through the posterior margin of the foramen of Monro. The choroid plexus in the atrium expands to a large tuft called the glomus. F, the body of the fornix has been removed to expose the internal cerebral veins coursing in the roof the third ventricle. The medial and lateral atrial and anterior calcarine veins join the posterior end of the internal cerebral veins. The basal veins are exposed below and lateral to the internal cerebral veins. Ant., anterior; Atr., atrial; Calc., calcarine; Caud., caudate; Cer., cerebral; Ch., choroidal; Chor., choroid; Comm., communicating; For., foramen; Int., intermedia, internal; Lat., lateral; Med., medial; Plex., plexus; M.P.Ch.A., medial posterior choroidal artery; Post., posterior; Sept., septal; Sup., superior; Thal.Str., thalamostriate; V., vein.

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FIGURE 4.19. A, posterosuperior view of the ventricles with the upper part of the cerebral hemisphere removed. The right occipital lobe and the adjacent tentorium have been removed to expose the upper surface of the cerebellum. Anterior caudate and anterior septal veins drain the walls of the frontal horn and empty into the anterior end of the internal cerebral vein. The posterior caudate veins drain the lateral wall of the body of the ventricle. B, enlarged view. The internal cerebral and basal veins converge on the vein of Galen. The lateral atrial vein crosses the pulvinar and empties into the internal cerebral vein. The anterior calcarine vein drains the depths of the calcarine sulcus and joins the vein of Galen near its junction with the basal vein. The calcarine sulcus forms a prominence, the calcar avis, in the medial wall of the atrium. The posterior end of the hippocampus is located at the anterior edge of the calcar avis. The veins exiting the ventricle pass through the margins of the choroidal fissure located between the fornix and thalamus. C, the section of the left cerebrum has been extended forward into the temporal horn and hippocampus. The inferior ventricular vein drains the roof of the temporal horn and passes through the choroidal fissure to empty into the basal vein. The lateral atrial vein crosses the posterior surface of the pulvinar to empty into the internal cerebral vein. Only the stump of the basal vein remains. D, enlarged view of the inferior ventricular vein passing through the choroidal fissure located between the fimbria and lower surface of the pulvinar, to join the basal vein. The deep end of the collateral sulcus, located on the lateral margin of the parahippocampal gyrus, forms a prominence, the collateral eminence, in the floor of the temporal horn lateral to the hippocampus. Ant., anterior; Atr., atrial; Calc., calcarine; Caud., caudate; Cer., cerebral; Chor., choroid, choroidal; Coll., collateral; Emin., eminence; Fiss., fissure; Inf., inferior; Int., internal; Lat., lateral; Parahippo., parahippocampal; Plex., plexus; Post., posterior; Sept., septal; Str., straight; Temp., temporal; Tent., tentorium; Thal. Str., thalamostriate; V., vein; Vent., ventricular.

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FIGURE 4.20. Inferior view of the basal cisterns. A, the basal veins are formed below the anterior perforated substance by the union of the posterior orbitofrontal, superficial and deep sylvian, and uncal veins and course posteriorly across the optic tracts. Only the anterior and posterior segments of the basal vein are exposed because the middle part is hidden above the uncus and parahippocampal gyrus. B, the uncus has an anterior and posterior segment. The lower part of the posterior segment of the right uncus and adjacent part of the parahippocampal gyrus has been removed, while preserving the fimbria of the fornix, to expose the inferior ventricular and lateral atrial veins. The segment of the right basal veins coursing lateral to the cerebral peduncle is very small. The inferior ventricular and lateral atrial veins pass through the choroidal fissure, situated between the thalamus and fimbria, to empty into the basal vein. The longitudinal hippocampal veins course along the fimbria. The peduncular veins, in this case, are quite small. The lateral atrial veins, which drain the lateral atrial wall and the posterior part of the roof of the temporal horn, pass below the pulvinar to reach the basal vein. C, enlarged view after removal of the fimbria. The large veins draining the roof of the temporal horn and lateral atrial wall and crossing the lower and posterior surface of the thalamus, are analogous to the thalamostriate vein that crosses the upper surface of the thalamus. All three veins drain a portion of the central core of the hemisphere and pass through the choroidal fissure between the thalamus and choroid plexus. D, the choroid plexus has been removed. Ant., anterior; Atr., atrial; Calc., calcarine; Chor., choroid; CN, cranial nerve; Gen., geniculate; Hippo., hippocampal; Inf., inferior; Lat., lateral; Long., longus; Ped., peduncle, peduncular; Perf., perforated; Plex., plexus; Post., posterior; Seg., segment; Subst., substance; Sup., superior; Temp., temporal; Tr., tract; V., vein; Vent., ventricular.

Frontal Horn

The frontal horn, the part of the lateral ventricle located anterior to the foramen of Monro, has a medial wall formed by the septum pellucidum, an anterior wall formed by the genu of the corpus callosum, a lateral wall composed of the head of the caudate nucleus, and a narrow floor formed by the rostrum of the corpus callosum. The columns of the fornix, as they pass anterior to the foramen of Monro, are in the posteroinferior part of the medial wall.

The medial group of veins in the frontal horn consists of the anterior septal veins, and the lateral group consists of the anterior caudate veins (Figs. 4.15, 4.16, and 4.18). The anterior septal veins are formed by tributaries from the deep white matter near the frontal pole. They course medially across the roof and anterior wall to reach the septum pellucidum, where they turn posteriorly toward the foramen of Monro, pass around the column of the fornix just above the foramen of Monro to enter the velum interpositum, and terminate in the internal cerebral vein. The anterior caudate veins are formed from small tributaries at the anterolateral and superolateral to the frontal horn, course on the ventricular surface of the head of the caudate nucleus, and terminate near the foramen of Monro in the thalamostriate or thalamocaudate veins. They may also empty directly into the internal cerebral vein.

Body of the Lateral Ventricle

The body of the lateral ventricle extends from the posterior edge of the foramen of Monro to the point where the septum pellucidum disappears and the corpus callosum and fornix meet. The roof is formed by the body of the corpus callosum, the medial wall by the septum pellucidum above and the body of the fornix below, the lateral wall is formed by the body of the caudate nucleus, and the floor is formed by the thalamus. The medial group of veins in the body is formed by the posterior septal veins, and the lateral group consists of the thalamostriate, thalamocaudate, and posterior caudate veins.

The thalamostriate is the best known of the subependymal veins because it is the one most frequently seen on angiography (Figs. 4.15, 4.16, and 4.18). In our study, it was present in 18 of the 20 hemispheres examined (20). The thalamostriate arises from tributaries that converge on the striothalamic sulcus located between the caudate nucleus and thalamus and passes toward the foramen of Monro, where it turns sharply posteriorly through the posterior margin of the foramen of Monro or the adjacent part of the choroidal fissure and enters the velum interpositum to join the internal cerebral vein. The angle formed by the junction of the thalamostriate and the internal cerebral veins at the thalamic tubercle, the venous angle, as seen on the lateral view of the cerebral angiogram, approximates the site of the foramen of Monro. In our study, the venous angle was situated 0 to 6.0 mm (average, 1.5 mm) from the posterior edge of the foramen of Monro (20). If the thalamostriate vein is absent, as occurred in two cases in our study, or is small, the thalamocaudate vein, which courses directly medial across the caudate nucleus and thalamus toward the choroidal fissure, drains the same area. In some cases, there are double thalamostriate veins, called the anterior and posterior thalamostriate veins, that course forward near the striothalamic sulcus and converge on the internal cerebral vein near the foramen of Monro.

The thalamocaudate vein courses medially across the caudate nucleus and thalamus behind the posterior extension of the thalamostriate vein and terminates in the internal cerebral vein (Figs. 4.15 and 4.16). The size of the thalamocaudate vein is inversely proportional to the size of the thalamostriate vein. If the thalamostriate vein is large and extends backward to the posterior part of the body, the thalamocaudate vein will be absent or small, and if the thalamostriate vein is absent, the thalamocaudate vein will be large. The thalamocaudate vein is not directed anteriorly along the striothalamic sulcus, as is the thalamostriate vein, but is directed medially or posteriorly across the lateral wall and floor of the body. It passes through the margin of the choroidal fissure well behind the foramen of Monro and ends in the internal cerebral, medial atrial, or posterior septal veins. The thalamocaudate vein was larger and the thalamostriate vein was absent in 4 of 20 hemispheres in our study (20).

The posterior caudate veins originate at the superolateral angle of the body and course inferomedial across the caudate nucleus toward the striothalamic sulcus, where they terminate in the thalamostriate or thalamocaudate veins. The posterior septal veins consist of one or two veins that originate along the roof of the body, course across the septum pellucidum, and terminate by penetrating the junction of the fornix and the septum pellucidum to enter the velum interpositum, where they join the internal cerebral vein. 

Atrium and Occipital Horn

The atrium and occipital horn together form a roughly triangular cavity, with the apex posteriorly in the occipital lobe and the base anteriorly on the pulvinar (Figs. 4.15 and 4.16). The lateral wall has an anterior part formed by the caudate nucleus and a posterior part formed by the fibers of the tapetum of the corpus callosum. The anterior wall has a medial part composed of the crus of the fornix and a lateral part formed by the pulvinar. The floor has a medial part composed of the hippocampus and a lateral part formed by the collateral trigone, the triangular prominence deep to the posterior end of the collateral sulcus. The occipital horn extends posteriorly into the occipital lobe from the atrium. Its size varies widely, from absence to extension far posteriorly in the occipital lobe, and its size may differ from one hemisphere to the other.

The medial group of veins in the atrium and occipital horn consists of the medial atrial veins, and the lateral group is composed of the lateral atrial veins (Figs. 4.4, 4.15, 4.16, 4.18– 4.21). The medial atrial veins drain forward on the medial wall of the atrium and occipital horn toward the choroidal fissure. They may also drain the adjacent part of the roof or floor. They pass through the choroidal fissure or crus of the fornix and terminate within the velum interpositum or quadrigeminal cistern in the internal cerebral or basal veins or their tributaries. The lateral atrial veins drain the anterior and lateral walls of the atrium and occipital horn and the adjacent part of the roof and floor. These veins course forward on the lateral wall across the tail of the caudate nucleus to reach the anterior wall, where they turn medially on the posterior surface of the pulvinar and pass through the choroidal fissure to reach the ambient or quadrigeminal cisterns. There they join the internal cerebral, basal, or great vein. The medial and lateral atrial veins may join near the choroidal fissure to form a common trunk called the common atrial vein.

The transverse hippocampal veins course medially across the collateral trigone and hippocampus on the floor of the temporal horn and penetrate the fimbria. They enter the ambient cistern by passing between the fimbria and dentate gyrus to terminate on the dentate gyrus in the posterior longitudinal hippocampal veins.

Temporal Horn

The temporal horn extends forward from the atrium below the pulvinar into the medial part of the temporal lobe and ends blindly in the anterior wall situated immediately behind the amygdaloid nucleus (Fig. 4.16). The floor is formed by the hippocampus and collateral eminence, the roof by the thalamus and caudate tail, the lateral wall by the tapetum, and the medial wall by the choroid fissure. The medial group of veins courses on the roof, and the lateral group of veins courses on the floor. The roof is drained predominantly by the inferior ventricular vein, with a lesser contribution from the amygdalar vein, and the floor is drained by the transverse hippocampal veins. The veins from the temporal horn join the basal vein or its tributaries. The posterior part of the roof and floor may be drained by the veins coursing in the walls of the atrium.

The inferior ventricular vein is in the posterolateral part of the roof of the temporal horn and courses obliquely anteromedial near the tail of the caudate nucleus (Figs. 4.4, 4.15, 4.16, and 4.19–4.21). It exits the temporal horn just behind the inferior choroidal point to join the basal vein near the lateral geniculate body at the junction of the crural and ambient cisterns. The amygdalar vein courses medially across the anterior wall on or near the ventricular surface of the amygdaloid nucleus. It terminates in the inferior ventricular, basal, or anterior longitudinal hippocampal vein near the inferior choroid point, either before or after it has passed through the choroidal fissure to enter the crural cistern. The amygdalar vein may receive the inferior choroidal veins and drain the adjacent part of the roof. The transverse hippocampal veins are a group of very fine veins that course medially across the hippocampal formation and collateral eminence. They penetrate the attachment of the fimbria to the hippocampus to enter the ambient cistern through the fimbriodentate sulcus to drain into the anterior and posterior longitudinal hippocampal veins.

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FIGURE 4.21. A-D. Territory of the basal vein. A, inferior view of the frontal lobe and anterior perforated substance with the optic chiasm reflected downward. The anterior cerebral veins pass above the optic chiasm and are joined across the midline by an anterior communicating vein. The anterior cerebral veins join the veins draining the posterior part of the orbital surface of the frontal lobe and the superficial and deep sylvian veins to constitute the anterior end of the basal vein. B, enlarged view of the anterior cerebral and anterior communicating veins. Paraterminal veins, draining the cortical areas below the genu of the corpus callosum, join the anterior cerebral veins near the junction with the anterior communicating veins. C, enlarged view of the right deep sylvian and anterior cerebral veins joining below the anterior perforated substance to form the anterior end of the basal vein. D, enlarged view of the large left superficial sylvian and smaller deep sylvian veins joining the anterior cerebral and olfactory veins to empty into the anterior end of the basal vein.

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FIGURE 4.21. E-H. E, inferior view of the basal cisterns in the same cerebrum. The medial part of the right parahippocampal gyrus has been removed to expose the temporal horn while preserving the uncus and the fimbria of the fornix. The left posterior cerebral artery and the medial temporal structures have been preserved. The lower lip of the right calcarine sulcus has been removed to expose the cuneus and anterior calcarine veins. The basal vein courses posteriorly around the cerebral peduncle and below the thalamus. The right anterior choroidal artery passes between the lateral geniculate body and the fimbria to reach the choroid plexus in the temporal horn. The left basal vein courses above the posterior cerebral artery. F, the left posterior cerebral artery has been removed to expose the basal vein. The anterior part of the left basal vein is hidden deep to the uncus. The right anterior and posterior longitudinal hippocampal veins course along the fimbria. G, the lower part of the posterior segment of the left uncus plus the parahippocampal gyrus and fimbria have been removed to expose the roof of the left temporal horn. The posterior segment of the left basal vein is missing, because the anterior part drained into a sinus in the tentorial that has been removed instead of draining into the vein of Galen. Uncal veins converge on the basal vein, as does the peduncular vein. The lateral atrial and thalamic veins converge on the calcarine vein. H, overview. The sylvian veins join the anterior cerebral veins to form the anterior end of the basal vein. The anterior cerebral veins are connected above the optic chiasm by the anterior communicating veins. The anterior segment of the right basal vein is larger than the left. The left atrial veins join the anterior calcarine vein before emptying into the vein of Galen. A., artery; A.C.A., anterior cerebral artery; A.Ch.A., anterior choroidal artery; Ant., anterior; Atr., atrial; Calc., calcarine; Car., carotid; Cer., cerebral; Chor., choroid; CN, cranial nerve; Comm., communicating; Hippo., hippocampal; Inf., inferior; Lat., lateral; Long., longus; Olf., olfactory; Paraterm., paraterminal; P.C.A., posterior cerebral artery; Ped., peduncle; Perf., perforated; Plex., plexus; Post., posterior; Subst., substance; Sup., superior; Temp., temporal; Tr., tract; V., vein; Vent., ventricular.

Choroidal Veins

The superior and inferior choroidal veins are the most consistent veins on the choroid plexus (Figs. 4.15, 4.16, and 4.18). The superior choroidal vein, the largest of the choroidal veins, runs forward on the choroid plexus in the body of the lateral ventricle and terminates near the foramen of Monro in the thalamostriate or internal cerebral veins or their tributaries. The inferior choroidal vein, the next most consistent choroidal vein, courses anteriorly in the temporal horn along the inferior end of the choroid plexus. It terminates by joining the inferior ventricular and amygdaloid vein or by passing through the choroidal fissure near the inferior choroidal point to reach the basal cisterns, where it terminates in the basal vein or its tributaries. The superior and inferior choroidal veins frequently anastomose through the veins draining the glomus of the choroid plexus.

Internal Cerebral Veins

The paired internal cerebral veins originate just behind the foramen of Monro and course posteriorly within the velum interpositum (Figs. 4.6, 4.15, 4.17–4.19, and 4.22). Initially, they follow the gentle convex upward curve of the striae medullaris thalami and, further distally, as they course along the superolateral surface of the pineal body, they follow the concave upward curve of the inferior surface of the splenium. The union of the paired veins to form the great vein may be located above or posterior to the pineal body and inferior or posterior to the splenium. The length of the internal cerebral vein varies from 19 to 35 mm (average, 30.2) (20).

The veins from the frontal horn, body, and part of the atrium terminate in the internal cerebral veins as they course through the velum interpositum. The tributaries of the internal cerebral vein from the lateral and third ventricles include the anterior septal, anterior caudate, posterior septal, posterior caudate, thalamostriate, thalamocaudate, anterior thalamic, anterior superficial thalamic, superior choroidal, superior thalamic, and superior superficial thalamic veins and the veins draining the striae medullaris thalami. The internal cerebral veins also receive numerous fine tributaries from the fornix, hippocampal commissure, choroid plexus of the third ventricle, and the thalamic surfaces forming the lateral walls of the third ventricle. Other veins that may join the internal cerebral, basal, or great veins include the medial and lateral atrial, posterior longitudinal hippocampal, internal occipital, and posterior pericallosal veins.

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FIGURE 4.22. Basal vein. A, lateral view with the right hemisphere removed. The internal cerebral veins course between the upper parts of the thalami. The basal vein courses posteriorly above the posterior cerebral artery. The nerves in the wall of the cavernous sinus have been exposed. B, superolateral view of the quadrigeminal cistern. The section of the brainstem extends through the cerebral peduncle and lateral geniculate body. The basal vein passes posteriorly above the posterior cerebral artery to join the internal cerebral vein in the quadrigeminal cistern. A vein courses parallel and below the basal vein connecting the veins in the quadrigeminal cistern and cerebellomesencephalic fissure with the superior petrosal veins emptying into the superior petrosal sinus. The trochlear nerve arises below the inferior colliculus. C, the right hemisphere including the thalamus has been removed to expose the basal vein coursing through the crural, ambient, and quadrigeminal cisterns and the internal cerebral veins coursing in the roof of the third ventricle. The hippocampus and fimbria have been preserved. The internal cerebral and basal veins course in close relationship to the fornix. The internal cerebral vein courses below the body of the fornix. The basal vein courses medial to the fimbria and the basal and internal cerebral veins join to form the vein of Galen in the area medial to the crus of the fornix. A column of the fornix and the anterior commissure are at the anterior margin of the exposure. D, the right temporal lobe, including the hippocampus and the choroid plexus, has been removed to expose the right basal vein passing through the ambient and quadrigeminal cistern. The roof of the temporal horn formed by the thalamus and tapetum of the corpus callosum is drained by the inferior ventricular vein that joins the basal vein by passing through the choroidal fissure. This basal vein in this case does not empty into the vein of Galen, but passes laterally below the temporal lobe to empty into a tentorial sinus. E, lateral view of another basal vein. The middle segment of this basal vein is hypoplastic. The posterior segment of the basal vein receives the inferior ventricular vein and passes around the midbrain to empty into the vein of Galen. The anterior part of the territory normally drained by the basal vein empties into the sylvian veins, leaving a hypoplastic midsegment lateral to the peduncle. F, anterosuperior view of the left basal vein coursing through the crural, ambient, and quadrigeminal cisterns. The basal vein arises at the union of the sylvian and anterior cerebral veins and passes posteriorly above the posterior cerebral artery in the crural cistern, located between the peduncle and uncus. It exits the crural cistern to enter the ambient cistern, located between the midbrain and parahippocampal gyrus, and terminates in the quadrigeminal cistern. The third nerve passes below the posterior cerebral artery. Medial atrial veins cross the medial atrial wall and empty into the veins in the quadrigeminal cistern. The internal cerebral vein courses in the roof of the third ventricle. A., artery; A.C.A., anterior cerebral artery; Ant., anterior; Atr., atrial; Car., carotid; Cer., cerebral; Cer.Mes., cerebellomesencephalic; CN, cranial nerve; Coll., collateral; Fiss., fissure; For., foramen; Gen., geniculate; Inf., inferior; Int., internal; Lat., lateral; M.C.A., medial cerebral artery; Med., medial; P.C.A., posterior cerebral artery; Ped., peduncle; Pet., petrosal; S.C.A., superior cerebellar artery; Sup., superior; Tent., tentorial; Tr., tract; V., vein; Vent., ventricle, ventricular; Verm., vermian.

Cisternal Group

The cisternal group of deep veins drains the area beginning anteriorly in front of the third ventricle and extending laterally into the sylvian fissure and backward to include the walls of the chiasmatic, interpeduncular, crural, ambient, and quadrigeminal cisterns (Figs. 4.17, and 4.19–4.22). The veins draining the structures anterior to the quadrigeminal cistern drain into the basal vein, and those in the region of the quadrigeminal cistern drain into the basal, internal cerebral, or great veins.

The area drained by the cisternal group of veins is divided into three regions depending on their relationship to the brainstem and tentorial incisura: an anterior incisural region located in front of the brainstem, a middle incisural region situated lateral to the brainstem, and a posterior incisural space located behind the brainstem (19). The incisural spaces are reviewed in detail in Chapter 5 of the Millennium issue of Neurosurgery (21). The major veins in the cisternal group are the basal and great veins.

The basal vein is formed below the anterior perforated substance by the union of veins draining the walls of the anterior incisural space. It proceeds posteriorly between the midbrain and the temporal lobe to drain the walls of the middle incisural space, and terminates within the posterior incisural space by joining the internal cerebral or great vein (Figs. 4.4 and 4.20–4.22). The basal vein is divided into anterior, middle, and posterior segments that correspond to the parts of the vein coursing within the anterior, middle, and posterior incisural regions. The anterior and middle incisural regions are drained, almost totally, by tributaries of the basal vein. The veins in the posterior incisural region join the internal cerebral and great veins, as well as the basal vein.

Anterior Incisural Region

The anterior incisural region is located anterior to the brainstem and extends upward around the optic chiasm to the subcallosal area and laterally below the anterior perforated substance into the sylvian fissure and over the surface of the insula (Figs. 4.4, 4.17, and 4.21). This region includes the walls of the subcallosal, chiasmatic, interpeduncular, and sylvian cisterns. The anterior perforated substance, on which numerous veins converge to form the basal vein, is in the central par of the roof of the anterior incisural space.

The cortical areas bordering the anterior incisural region, which may also be drained by the basal vein, include the insula and the orbital surface of the frontal lobe. The insular veins, one of the major contributing groups to the first part of the basal vein, are named for their relationship to the insular sulci and gyri.

The major venous structure in the anterior incisural space is the anterior segment of the basal vein (Figs. 4.4, 4.17, and 4.21). This segment begins at the union of the deep middle cerebral and anterior cerebral veins, below the anterior perforated substance, and passes posteriorly to end where the peduncular vein joins the basal vein at the anterolateral part of the cerebral peduncle. The tributaries of this segment are the deep middle cerebral, anterior cerebral, insular, orbitofrontal, olfactory, uncal, peduncular, and inferior striate veins. In our study, two hemispheres lacked an anterior segment of the basal vein (20). A number of these veins may join before emptying into the basal vein.

The deep middle cerebral vein is formed by the union of the insular veins near the limen insula. It passes medially across the anterior perforated substance, where it unites with the anterior cerebral vein to form the basal vein. The deep middle cerebral vein, the anterior segment of the basal vein, or their tributaries may be connected by a bridging vein to the sphenoparietal or cavernous sinus.

The veins draining the insula empty predominantly through the deep middle cerebral vein into the basal vein, but some may terminate in the superficial cortical veins bordering the sylvian fissure (Fig. 4.23). The anterior cerebral veins originate near the upper margin of the optic chiasm and are often joined across the midline by the anterior communicating vein. They course along the superolateral boundary of the optic chiasm and tract, and terminate, most commonly, by joining the deep middle cerebral vein. The orbitofrontal veins consist of one or more veins that drain the orbital surface of the frontal lobe and empty into the anterior end of the basal vein or its tributaries. The olfactory vein courses on the inferior surface of the frontal lobe, near the olfactory sulcus, and terminates in the tributaries of the basal vein.

The inferior striate veins exit the anterior perforated substance and join the deep middle cerebral and basal veins. They drain a large area above the anterior perforated substance that includes the putamen, caudate nucleus, and internal capsule. In the lateral view of the cerebral venogram, they have a fan-shaped appearance and converge to an apex at the anterior perforated substance. The peduncular vein originates on the posterior perforated substance, courses laterally around the cerebral peduncle, and usually joins the basal vein at the junction of the anterior and middle cerebral incisural spaces. Small veins from the anterior part of the medial surface of the uncus cross the anterior incisural space and terminate in the deep middle cerebral vein or the anterior part of the basal vein.

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FIGURE 4.23. A, sylvian and insular veins. Lateral view of the sylvian fissure. The posterior two-thirds of the superficial sylvian vein is larger than the anterior third, which is very small. The large posterior segment of this superficial sylvian vein joins the vein of Labbé and the anterior end joins an anastomotic vein crossing the frontal lobe. Duplicate anastomotic veins fitting the criteria for a vein of Trolard connect the sagittal sinus to the sylvian veins: one crosses the frontal lobe and the other crosses the parietal lobe. The lip of the sylvian fissure has been retracted to expose a small deep sylvian vein, which crosses the insula and passes medially below the anterior perforated substance to join the basal vein. The lower retractor is on the planum polare, an area free of gyri on the upper surface of the temporal lobe. Further posteriorly on the upper surface of the temporal lobe are the transverse temporal gyri that form the planum temporale. B, enlarged view of another specimen. The lower opercular lip has been retracted to expose the deep sylvian veins passing around the lumen insula to course below the anterior perforated substance and join the anterior end of the basal vein. C, the frontoparietal operculum has been removed. The veins draining the opercular lips and insula pass predominantly to the large superficial sylvian vein rather than forming a large deep sylvian vein. D, another specimen showing the veins on the insula converging to form a deep sylvian vein that passes above the middle cerebral artery and below the anterior perforated substance to join the anterior end of the basal vein. The most anterior of the transverse temporal gyri is Heschl’s gyrus. Dup., duplicate; Mid., middle; Sup., superior; Temp., temporal; Trans., transverse; V., vein.

Middle Incisural Space

The middle incisural region, which is drained by the middle segment of the basal vein, is located between the midbrain  and the temporal lobe (Figs. 4.4, 4.17, and 4.20–4.22). Its anterior part contains the crural cistern, and its posterior part contains the ambient cistern. The venous relationships in the middle incisural space are relatively simple. The major venous trunk in this space is the middle segment of the basal vein, which courses along the upper part of the cerebral peduncle and below the pulvinar to reach the posterior incisural space. The basal vein may infrequently terminate in a tentorial sinus in the free edge at this level. The tributaries of this segment of the basal vein are from the temporal horn and medial temporal surface, including the uncus and lateral midbrain. The veins in this area are as follows: the inferior ventricular vein, which drains the roof of the temporal horn; the anterior longitudinal hippocampal vein, which courses anteriorly along the dentate gyrus toward the inferior choroidal point; the anterior hippocampal vein, which originates on the uncus and the posterior portion of the amygdaloid nucleus and proceeds posteriorly along the anterior hippocampal sulcus to form a common stem with the inferior ventricular or anterior longitudinal hippocampal vein; the lateral mesencephalic vein, which courses along the lateral mesencephalon; the temporal cortical veins from the posterior two-thirds of the uncus; and the medial temporal veins from the adjacent part of the parahippocampal and occipitotemporal gyri.

Posterior Incisural Region

The posterior incisural space is situated posterior to the midbrain and corresponds to the pineal region (Figs. 4.9, 4.17, 4.19, 4.22, and 4.24). This space is occupied by the quadrigeminal cistern. The venous relationships in the posterior incisural region are the most complex in the cranium because the internal cerebral, basal, and great veins and many of their tributaries converge on this area. The internal cerebral veins exit the velum interpositum to reach the posterior incisural space, where they join to form the vein of Galen. The posterior segment of the basal vein begins at the posterior margin of the ambient cistern, where the vein passes to the posterior margin of the midbrain to reach the quadrigeminal cistern, and it terminates in the internal cerebral or great veins. If the posterior segment of the basal vein is absent, the middle segment drains into a sinus in the tentorial edge. The great vein passes below the splenium to enter the straight sinus at the tentorial apex. The junction of the vein of Galen with the straight sinus varies from being nearly flat if the tentorial apex is located below the splenium to forming an acute angle if the tentorial apex is located above the level of the splenium, so that the great vein must turn sharply upward to reach the straight sinus at the tentorial apex.

The tributaries of the internal cerebral, basal, and great veins in the quadrigeminal cistern are as follows: the atrial veins, which are described above, under Ventricular Veins; the posterior longitudinal hippocampal vein, which courses along the posterior portion of the dentate gyrus; the posterior pericallosal vein, which courses around the posterior surface of the splenium; the superior vermian vein, the largest vein from the infratentorial part of the posterior incisural space, which arises on the vermic surface forming the floor of the posterior incisural space and receives the superior hemispheric veins from the adjacent cerebellar surface and the vein of the cerebellomesencephalic fissure and empties into the great vein; the tectal veins originating on or near the superior and inferior colliculi; the epithalamic veins, which emerge from the posterior part of the third ventricle in the region of the pineal body and drain the posteromedial part of the thalamus and adjacent epithalamic areas, including the pineal body, posterior and habenular commissures, and neighboring portions of the thalamus—the most posterior of the medial temporal veins draining the posterior part of the parahippocampal and occipitotemporal gyri; the medial occipitotemporal veins, which arise on the lingula and the occipitotemporal gyri; the internal occipital veins, which originate in the area of the calcarine and parietooccipital sulci; and the thalamic veins from the superior and medial portions of the thalamus that drain into the internal cerebral or great veins, and these form the inferior and lateral portions of the thalamus, which drain into the basal vein or its tributaries. The term, thalamostriate vein, implies a relationship with the thalamus but, despite its course along the lateral margin of the thalamus, none of the thalamic veins join it.

The deep thalamic veins are divided into anterior, superior, inferior, and posterior thalamic veins. The anterior thalamic vein drains the anterior portion of the thalamus and terminates in the adjacent part of the internal cerebral, anterior septal, thalamostriate, or anterior caudate vein, or other smaller veins in the region. The superior thalamic vein is the largest of the thalamic veins. It arises in the central superior part of the thalamus, runs medially to emerge from the mesial surface of the thalamus near the striae medullaris thalami, runs posteriorly below the internal cerebral vein in the velum interpositum, and ends in the internal cerebral or the great vein. The inferior thalamic veins arise in the anteroinferior part of the thalamus and traverse the posterior perforated substance to drain into the posterior communicating or peduncular vein.

The posterior thalamic veins drain the posterior inferolateral portion of the thalamus and empty into the posterior part of the basal vein or the veins coursing on the posterolateral surface of the midbrain. The superficial thalamic veins course along the ventricular surface of the thalamus in a subependymal location and drain into the adjacent veins in the ventricle, velum interpositum, or basal cisterns.

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FIGURE 4.24. Venous relationships in the quadrigeminal cistern. A, neural structures in the quadrigeminal cistern. The anterior wall of the quadrigeminal cistern is formed by the pulvinar, superior, and inferior colliculi and the superior cerebellar peduncles. The cistern extends downward between the cerebellum and midbrain into the cerebellomesencephalic fissure. The roof of the third ventricle, anterior to the pineal, has been opened. The striae medullaris thalami extend forward along the lateral wall of the third ventricle, beginning posteriorly at the habenular commissure. The right temporal horn, uncus, and cerebral peduncle have been exposed. B, the internal cerebral and basal veins join in the quadrigeminal cistern to form the vein of Galen. The posterior cerebral arteries enter the upper part of the quadrigeminal cistern and the superior cerebellar arteries enter the lower part. The trochlear nerve courses between the superior cerebellar and posterior cerebral arteries. C, infratentorial exposure of the venous complex in the supracerebellar area. The basal, internal cerebral, anterior calcarine, and superior vermian veins converge on the vein of Galen. The left posterior cerebral artery gives rise to a branch that enters the lower surface of the tentorium. D, another specimen. The internal cerebral, basal, and anterior calcarine veins converge on the vein of Galen. E and F, occipital transtentorial exposure. E, the occipital lobe has been retracted and the tentorium divided adjoining the straight sinus to expose the quadrigeminal cistern. F, enlarged view. The exposure extends forward to the margin of the cerebral peduncle, uncus, and the crural cistern. The basal vein passes around the brainstem on the medial side of the temporal lobe to reach the quadrigeminal cistern. The internal cerebral veins exit the roof of the third ventricle and empty into the vein of Galen. A combined supra- and infratentorial exposure can be obtained by dividing the transverse sinus and tentorium, but should only be considered if there is a nondominant transverse sinus on the side of the exposure. Ant., anterior; Calc., calcarine; Cer., cerebellar; Cer.Mes., cerebellomesencephalic; Chor., choroid; CN, cranial nerve; Coll., collateral; Fiss., fissure; Inf., inferior; Int., internal; Med., medial; M.P.Ch.A., medial posterior choroidal artery; P.C.A., posterior cerebral artery; Ped., peduncle; Plex., plexus; S.C.A., superior cerebellar artery; Str., straight; Sup., superior; Temp., temporal; Tent., tentorial, tentorium; Thal., thalamus; V., vein; Vent., ventricle; Verm., vermian.

Discussion and Operative Approaches

The distribution of the superficial cortical veins is not as irregular and variable as is generally supposed, and their examination during the venous phase of the cerebral angiogram may prove helpful in localizing expanding lesions by revealing poor filling and displacement and alteration in the direction of flow. Although the majority of the superficial cortical veins do not course along the sulci, some may be helpful in locating the sulci. The veins that most commonly approximate the position of a sulcus (and their respective sulci) are the superficial sylvian veins and the sylvian fissure, the precentral vein and the precentral sulcus, the central vein and the central sulcus, the postcentral vein and the postcentral sulcus, the anteromedial parietal vein and the ascending ramus of the cingulate sulcus, the posteromedial parietal vein and the parieto-occipital sulcus, and the anterior and posterior pericallosal veins and the anterior and posterior parts of the callosal sulcus. The tendency of these veins to approximate the position of a sulcus becomes less prominent as the veins approach the sinuses.

There is considerable variation in the size of the individual cortical veins, not only in different brains, but also from side to side in the same brain. The veins on the lateral surface are larger than those on the medial and inferior surfaces. The largest veins on the lateral surface are usually in the region of the central sulcus. The veins on the lateral surface are arranged like the spokes of a wheel; they radiate outward from the stem of the sylvian fissure. The three largest pathways of cortical drainage on the lateral surface are through the veins of Trolard and Labbé and the superficial sylvian veins (Figs. 4.10 and 4.11). According to DiChiro (7), the vein of Labbé predominates in the dominant hemisphere nearly twice as often as it predominates in the nondominant hemisphere, and the vein of Trolard predominates in the nondominant hemisphere with approximately the same frequency.

The fact that sacrifice of the individual cortical veins only infrequently leads to venous infarction, hemorrhage, swelling, and neurological deficit is attributed to the diffuse anastomoses between the veins. There are abundant anastomoses between the individual cortical veins draining adjacent cortical areas and between the superficial cortical veins and the deep ventricular and cisternal veins. There are also anastomoses along the borders of the hemisphere between the veins draining the adjacent parts of the lateral, medial, and basal surfaces. The latter anastomoses are located at the terminal ends of the veins just proximal to where the bridging veins enter the dural sinuses.

Obliteration of the superficial and deep bridging veins, including the great, basal, and internal cerebral veins, is inescapable in some operative approaches; however, the number of these veins and their branches to be sacrificed should be kept to a minimum because of the possible undesirable sequelae, which, although usually transient, may be permanent. Before sacrificing these veins, the surgeon should try to work around them, displacing them out of the operative route, or placing them under moderate or even severe stretch, accepting the fact that they may be torn, if this will yield some possibility of their being saved. Another option is to divide only a few of their small tributaries, which may allow the displacement of the main trunk out of the operative field. The natural reluctance to sacrifice a bridging vein should be increased if the vein in the operative exposure seems larger than normal (Fig. 4.12). The increase in size usually signifies that the vein drains a larger area than normal and increases the likelihood of ill effect if it is sacrificed. In some cases, a large vein of Trolard or Labbé or a large superficial sylvian vein may drain the majority of the lateral surface of a hemisphere. Occlusion of the bridging veins formed by the terminal end of several cortical veins causes more difficulty than sacrifice of a bridging vein formed by the terminal end of one vein or obliteration of the individual vein on the cortical surface.

In opening the dura mater adjoining the superior sagittal sinus, one should attempt to preserve the meningeal sinuses, which may arise as far as 2.5 cm lateral to the superior sagittal sinus (Fig. 4.2, C and D). These sinuses may receive the terminal end of numerous cortical veins. In removing a parasagittal tumor deep to these sinuses, the dura is opened along the edges of the sinus while preserving the sinus’ proximal junction with the cortical veins and its distal junction with the superior sagittal sinus. The tumor is then separated from the lower margin of the meningeal sinus without sacrificing the sinus.

The lacunae may present a significant obstacle in operative approaches to the parasagittal region, where they spread out over the upper extent of the precentral, central, and postcentral gyri (Fig. 4.3). The lacunae are reported to be absent in the fetus and increase in size with advancing age (17). The increase in the size of the lacunae is accompanied by an increase in the size of the pacchionian granulations that project into the lacunae. The lacunae may extend along the medial extent of the hemisphere adjacent to the falx and as far as 3 cm laterally over the convexity. Entering or occluding a lacuna at operation does not necessarily result in occlusion of the cortical veins or the superior sagittal sinus because most of the veins course deep to the lacunae and usually empty into the sinus separately from the lacunae. The lacunae, even when large, do not have a diffuse communication with the superior sagittal sinus, but open into it through smaller apertures, which may be occluded without loss of patency of the sinus. Parasagittal meningiomas usually arise from the arachnoid granulations in the lacunae and do not necessarily occlude the adjacent cortical veins, which frequently course under rather than through the lacunae to reach the superior sagittal sinus. These veins should be carefully separated from the deep margin of the tumor by micro-operative techniques, rather than obliterating them when they are exposed along the margin of the tumor.

The operative approach directed along the falx toward the anterior part of the corpus callosum may require the sacrifice of a bridging vein to the superior sagittal sinus. Occasionally, the corpus callosum may be reached in the area between the anterior and posterior frontal veins without sacrificing any bridging veins because there is frequently a several-centimeter segment of the superior sagittal sinus between the anterior and middle frontal veins or between the middle and posterior frontal veins where no tributaries join the superior sagittal sinus (Fig. 4.14). Obliteration of the bridging veins to the superior sagittal sinus in the region of the precentral, central, or postcentral gyri frequently causes a contralateral hemiparesis that is more prominent in the lower than the upper extremity and is usually transient. Spontaneous occlusion of the veins in this region causes a hemiparesis that is commonly accompanied by headache and seizures (12, 14). The bridging veins joining the inferior sagittal sinus, which arise from the upper end of the anterior pericallosal vein, are infrequently mentioned in discussing the transcallosal operative approaches. These veins vary in size from a tiny tuft that drains a small cortical area to several large veins that drain both the upper portion of the corpus callosum and most of the adjacent part of the medial surface of the frontal lobes.

In the subfrontal approach, bridging veins are rarely encountered in the area between the frontal lobe and the orbital roof. The anterior end of the basal vein may be seen below the anterior perforated substance (Figs. 4.4 and 4.21). The veins most commonly sacrificed in this approach are those along the medial part of the exposure, which drain into the anterior end of the superior sagittal sinus, and those on the lateral side of the exposure, which empty into the sphenoparietal and cavernous sinuses adjacent to the sphenoid ridge. The posterior part of the orbital surface of the frontal lobe can usually be retracted away from the upper surface of the sphenoid ridge without sacrificing any veins because most of the tributaries along the sphenoid ridge join the sphenoparietal sinus below the edge of the ridge.

Reaching lesions in the basal cisterns by the frontotemporal (pterional) and subtemporal approaches may require the sacrifice of one or more bridging veins entering the dual sinuses adjacent to the sphenoid ridge, which courses toward the cavernous sinus (Figs. 4.5 and 4.12). It is often necessary to sacrifice one or more of the veins entering the sphenoparietal, sphenobasal, or cavernous sinus to retract the temporal pole away from the adjacent part of the sphenoid ridge. It may be possible to preserve the bridging veins entering the sinuses along the sphenoid ridge if the frontotemporal approach is entirely above the sphenoid ridge or if the subtemporal approach is entirely below the temporal pole. It is usually necessary to sacrifice some of the superficial or deep sylvian bridging veins if both the posterior frontal area and the temporal tip are retracted away from the sphenoid ridge. Obliteration of the superficial or deep sylvian veins along the sphenoid ridge may cause seizures and a facial palsy plus aphasia if the occlusion is on the left side (2, 13).

Many bridging veins are encountered further posteriorly under the temporal lobe (Fig. 4.5). These veins include the temporal, occipital, temporobasal, and occipitobasal veins and the vein of Labbé. Sacrifice of these veins, which pass from the lower part of the hemisphere to the transverse and tentorial sinuses, frequently causes some degree of venous infarction and edema of the temporal lobe. A contralateral hemiparesis, more marked in the face and arm than the leg, with an aphasia if the dominant hemisphere is affected, may follow occlusion of these veins (4). The reason for the frequent difficulties encountered after retraction of the temporal lobe away from the area above the junction of the transverse and superior petrosal sinuses is that the veins from most of the lateral and basal surfaces of the temporal lobe converge on this area. These sequelae, encountered after the subtemporal operative approaches, are frequently ascribed to occlusion of the vein of Labbé; however, it is infrequent that only the vein of Labbé is sacrificed in these approaches, because there are numerous other bridging veins in the region that must also be sacrificed if the subtemporal operative exposure extends medial under the temporal lobe to the tentorial incisura.

In the occipital transtentorial operative approach, the occipital pole can usually be retracted from the straight sinus and the junction of the falx and the tentorium without sacrificing any veins to the superior sagittal or transverse sinuses (Fig. 4.2). The superior sagittal sinus is commonly devoid of bridging veins in the area just in front of the torcular herophili, but bridging veins are encountered if the exposure is directed further forward along the superior sagittal sinus in the posterior parietal area. The posterior calcarine vein, which empties into the veins on the lateral surface and into the superior sagittal sinus 4 to 9 cm proximal to the torcular herophili, is infrequently encountered in the occipital transtentorial approaches. However, the anterior calcarine (internal occipital) vein, which crosses at a much deeper level, frequently blocks access to the quadrigeminal cistern as it passes from the anterior end of the calcarine fissure to the great vein, thus making its obliteration unavoidable in reaching some tumor in the pineal region (Figs. 4.9 and 4.24). Sacrificing the anterior calcarine vein may cause a homonymous hemianopsia. No bridging veins pass directly from the occipital lobe to the straight sinus.

The medial and lateral tentorial sinuses may be encountered in the operative approaches in which the tentorium is divided (Figs. 4.4 and 4.5). The medial tentorial sinus would be encountered in incising the tentorium from anterior to posterior adjacent to the straight sinus, as might be conducted in an occipital transtentorial or infratentorial supracerebellar approach. The lateral tentorial sinus would be encountered in the lateral part of an incision in the tentorium extending from the free edge toward the transverse sinus in the area just behind the petrous ridge, as would be conducted in a subtemporal approach to the front of the brainstem. The veins that arise on the brainstem and cerebellum and drain into the superior petrosal sinus are also encountered in sectioning the anteromedial edge of the tentorium through a subtemporal craniectomy to expose the trigeminal nerve. The temporobasal bridging veins, which have relatively strong adhesions to the dura mater of the middle fossa and the superior surface of the tentorium, could be injured proximal to their termination during elevation of the temporal lobe in the course of a subtemporal operative approach to the basal cisterns.

The deep cerebral veins may pose a major obstacle to operative approaches to deep-seated lesions, especially in the pineal region, where multiple veins converge on the great vein (Figs. 4.9, 4.17, and 4.24) (25, 31). The fact that sacrifice of the major trunks of the deep venous system only infrequently leads to venous infarction with mass effect and neurological deficit is attributed to the diffuse anastomoses between the veins. Dandy (5) noted that, not infrequently, one internal cerebral vein has been sacrificed without effect and, on a few occasions, both veins and even the great vein have been ligated with recovery without any apparent disturbance of function. On the other hand, injury to this complicated venous network has caused diencephalic edema, mental symptoms, coma, hyperpyrexia, tachycardia, tachypnea, miosis, rigidity of limbs, and exaggeration of deep tendon reflexes (2, 15, 27, 28). Occlusion of the thalamostriate and other veins at the foramen of Monro may cause drowsiness, hemiplegia, mutism, and hemorrhagic infarction of the basal ganglia (11). The ventricular veins provide valuable landmarks in directing the surgeon to the foramen of Monro and the choroidal fissure during operations on the ventricles (Figs. 4.18 and 4.19). This is especially true if hydrocephalus, a common result of ventricular tumors, is present, because the borders between the neural structures in the ventricular walls become less distinct as the ventricles dilate. The thalamostriate vein is helpful in delimiting the junction of the caudate nucleus and the thalamus because it usually courses along the sulcus separating these structures.

The fact that the ventricular veins converge on the choroidal fissure assists in identifying this fissure, which is situated on the periphery of the thalamus and through which operative procedures may be directed to the third ventricle, pineal region, and crural, ambient, and quadrigeminal cisterns (Figs. 4.16 and 4.18–4.21). Opening through the choroidal fissure in the body of the ventricle will expose the velum interpositum and the roof of the third ventricle; opening through the fissure in the atrium will expose the quadrigeminal cistern and the pineal region; and opening through the fissure in the temporal horn will expose the crural and ambient cisterns. The venous drainage of arteriovenous malformations and tumors fed by the choroidal arteries will drain through the margin of the choroidal fissure to reach the major deep venous trunks. The arterial supply of these malformations also commonly passes through the choroidal fissure (8, 10, 22).

In the anterior transcortical or transcallosal approach through the anterior part of the corpus callosum, the veins in the frontal horn are seen to drain posteriorly toward the foramen of Monro, because the choroidal fissure does not extend into this area. The anterior caudate, anterior septal, superior choroidal, and thalamostriate veins usually join the internal cerebral veins at or near the foramen of Monro. However, these veins may pass through the choroidal fissure behind the foramen of Monro to enter the velum interpositum and course adjacent to the internal cerebral vein for a considerable distance before joining the internal cerebral vein. The junction of the thalamostriate vein with the internal cerebral vein, as seen on the lateral angiogram, usually forms an acute angle at the posterior margin of the foramen of Monro; however, the thalamostriate vein may pass through the choroidal fissure and join the internal cerebral vein posterior to the foramen of Monro, thus suggesting on the angiogram that the foramen of Monro is shifted posteriorly when it is not.

The internal cerebral vein is not seen on opening into the frontal horn because it courses in the roof of the third ventricle below the body of the fornix (Fig. 4.18). The anterior part of the internal cerebral vein can be exposed only by opening through or displacing the structures forming the roof of the third ventricle. One method of increasing the exposure of the roof of the third ventricle is to section a column of the fornix anterosuperior to the foramen on one side, but this will permit the exposure of no more than a short anterior segment of the internal cerebral vein. To prevent the complications associated with sectioning the fornix, Hirsch et al. (11) sectioned the thalamostriate vein at the posterior margin of the foramen of Monro, rather than damaging the fornix to enlarge the opening in the roof of the third ventricle. They stressed that interruption of this vein was harmless; however, some of their patients developed drowsiness, hemiplegia, and mutism, and occlusion of the veins at the foramen of Monro has caused hemorrhagic infarction of the basal ganglia. Other routes to the anterior part of the internal cerebral vein are by the interforniceal approach, in which the body of the fornix is split in the midline and the tela choroidea below the fornix is opened to expose the internal cerebral veins, or by the transchoroidal approach, in which the choroidal fissure is opened between the fornix and thalamus, thus allowing the fornix to be pushed to the opposite side to expose the structures in the roof of the third ventricle (1, 30). The transchoroidal and interforniceal approaches have the advantage of giving access to the central portion of the third ventricle by displacing, rather than dividing, the fibers in the fornix. These approaches are reviewed in detail in Chapter 5.

In the transcortical approach to the posterior part of the body and atrium of the lateral ventricle, the medial and lateral atrial, posterior septal, posterior caudate, and thalamocaudate veins will be seen to converge on the choroidal fissure, which, in this area, is located between the crus of the fornix and the pulvinar. These veins join the posterior end of the internal cerebral vein in the velum interpositum or the basal, internal cerebral, or great vein in the quadrigeminal cistern. To reach these veins by the transventricular approaches, the surgeon must open through the choroidal fissure or the crus of the fornix.

In these approaches through the temporal horn, the inferior ventricular vein in the roof of the temporal horn and the smaller transverse hippocampal veins in the floor of the temporal horn will be seen to converge on the choroidal fissure (Figs. 4.16 and 4.19–4.21). After entering the temporal horn, the choroidal fissure is opened to expose the crural and ambient cisterns and the basal peduncular, lateral mesencephalic, basal hippocampal, and inferior ventricular veins.

Lesions medial to the atrium in the quadrigeminal cistern may be reached from above the tentorium along the inferomedial surface of the occipital lobe using an occipital-transtentorial approach, through the posterior part of the lateral ventricle using a posterior transventricular approach, through the corpus callosum using a posterior interhemispheric-transcallosal approach, or from below the tentorium through the supracerebellar space using an infratentorialsupracerebellar approach. The infratentorial-supracerebellar approach is selected for many lesions because the deep venous system that caps the dorsal aspect of pineal tumors does not obstruct access to the tumor. The occipital-transtentorial approach is preferred for lesions centered at or above the tentorial edge and above the vein of Galen. The posterior transcallosal approach, in which the splenium is divided, would be used only if the lesion seems to arise in the splenium above the vein of Galen. The posterior transventricular approach through the superior parietal lobule may provide the optimal approach to a tumor involving the quadrigeminal cistern if the tumor extends into the pulvinar or involves the atrium or glomus of the choroid plexus. The approaches to the ventricle are reviewed in detail in Chapter 5.

Content from Rhoton AL. The Supratentorial Cranial Space: Microsurgical Anatomy and Surgical Approaches. Neurosurgery 51(1), 2002, 10.1097/00006123-200210001-00001. With permission of Oxford University Press on behalf of the Congress of Neurological Surgeons.

The Neurosurgical Atlas is honored to maintain the legacy of Albert L. Rhoton Jr., MD

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