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Orbit

Last Updated: August 20, 2020

Introduction

The orbit is the complexly organized group of neural, vascular, muscular, ligamentous, and osseous structures that opens onto the face and external world to collect and provide binocular visual information to the brain. The retina, which captures visual information, is protected from external trauma, overexposure, and excessive light by the eyelids and a precisely organized mechanism for modulating light reaching the biological visual screen. The globe is surrounded by a precisely coordinated group of muscles encased in fat to allow free movement of the globe and muscles, but limited at the extremes by ligamental structures to prevent excessive mobility. Nearly all of the bones forming the anterior and middle cranial base contribute to the formation of the orbit’s walls. The orbit communicates posteriorly with the anterior and middle cranial fossae and inferiorly with the pterygopalatine and infratemporal fossa. The nerves and vessels entering and exiting the orbit pass through the optic canal and superior orbital fissure, which are partially surrounded by an annular tendon, from which the rectus muscles arise. The fact that many of the neural and vascular structures entering the orbit pass through not only an osseous channel, but also through the annular tendon, creates an added complexity when considering approaches to the orbit and especially those involving the orbital apex. The orbit can be approached surgically from anteriorly through the face and conjunctivae or through any of its walls and from intracranially. The most common neurosurgical approaches are directed through the superior and lateral walls to lesions located deep in the orbit near the apex or involving the optic canal, superior orbital fissure, and adjacent areas (21, 22, 24).

Osseous Relationships

The walls of the orbit are formed by seven bones: frontal, zygomatic, sphenoid, lacrimal, ethmoid, and palatine bones and the maxilla (Fig. 7.1). The upper border of the orbital opening is formed by the frontal bone, which is notched or is the site of one or several small foramina that transmit the supraorbital and supratrochlear nerves and vessels. The lateral border of the orbital opening is formed by the frontal process of the zygomatic bone, except for the upper part, which is formed by the zygomatic process of the frontal bone. The lower margin of the orbital opening is formed laterally by the zygomatic bone and medially by the maxilla. The upper part of the medial border is formed by the frontal bone and the lower part is formed by the frontal process of the maxilla. The medial part of the upper border contains the frontal sinus.

The anterior part of the orbital roof is formed by the orbital plate of the frontal bone, and the posterior part is formed by the lesser wing of the sphenoid bone, which also forms most of the sphenoid ridge (Figs. 7.1 and 7.2). The sphenoid and ethmoid bones are interposed between the orbital roofs. The ethmoid bone is the site of the cribriform plate and the upward-projecting crista galli to which the falx attaches. Anteriorly, the frontal bone splits into two laminae, which enclose the frontal sinuses. The lacrimal fossa, the depression in which the lacrimal gland rests, is located below the anterolateral part of the roof. Another small depression in the anteromedial part of the roof, the trochlear fossa, serves as the attachment for the trochlea of the superior oblique muscle.

The floor of the orbit is formed by the orbital plate of the maxilla, the orbital surface of zygomatic bone, and the orbital process of the palatine bone. The orbital floor, which is very thin, forms the roof of the maxillary sinus. The floor is continuous with the medial wall, except in the most anterior part, where the floor is perforated by the nasolacrimal canal. The anterior part of the floor is continuous with the lateral wall, but posteriorly, the floor and lateral wall are separated by the inferior orbital fissure. The infraorbital groove, which transmits the infraorbital branch of the maxillary nerve, leads forward out of the inferior orbital fissure to cross the floor to reach the infraorbital canal, which ends below the lower orbital rim in the infraorbital foramen.

The lateral wall consists predominantly of the greater sphenoid wing and the frontal process of the zygomatic bone. The greater sphenoid wing also forms much of the middle fossa floor and the roof of the infratemporal fossa. Superiorly, the anterior part of the lateral orbital wall is continuous with the roof, but the posterior part of the lateral wall is separated from the roof by the superior orbital fissure. The lacrimal foramen, which transmits the recurrent meningeal branch of the ophthalmic artery, is located anterior to the superior orbital fissure along the superior edge of the lateral wall. The zygomatico-orbital foramina on the anterolateral part of the intraorbital surface of the lateral wall transmit the zygomaticofacial and zygomaticotemporal nerves, which exit the external surface of the zygoma at the zygomaticofacial and zygomaticotemporal foramina to reach the skin of the cheek and temple.

The medial wall is formed, from anterior to posterior, by the frontal process of the maxilla, the lacrimal bone, the orbital plate of the ethmoid bone, and the body of the sphenoid bone. The medial wall is extremely thin, especially in the area of the orbital plate of the ethmoid bone, which separates the orbit and ethmoid air cells. The lacrimal sac, which sits in the lacrimal groove formed by the frontal process of the maxilla anteriorly and the lacrimal bone posteriorly, opens into the nasal cavity through the nasolacrimal canal. The anterior and posterior ethmoidal foramina, which transmit the anterior and posterior ethmoidal branches of the ophthalmic artery and the nasociliary nerve, are located at the junction of the roof and medial wall of the orbit and pass through the frontoethmoidal suture or the adjacent part of the frontal bone and open into the anterior cranial fossa along the lateral edge of the cribriform plate.

The optic canal, through which the optic nerve and ophthalmic artery pass, opens into the superomedial corner of the orbital apex at the junction of the roof and medial wall. The optic canal is situated at the junction of the lesser wing with the body of the sphenoid bone. It is separated from the superior orbital fissure by the optic strut, a bridge of bone, also referred to as the posterior root of the lesser wing, which extends from the lower margin of the base of the anterior clinoid process to the sphenoid body. The tendinous ring (annular tendon) from which the superior, inferior, medial, and lateral rectus muscles arise, is attached to the upper, lower, and medial margin of the optic canal. The anterior clinoid process projects backward from the lesser wing of the sphenoid bone into the interval between where the optic nerve enters the optic canal and where the oculomotor nerve enters the superior orbital fissure.

The intracranial end of the optic canal has an ovoid shape with a slightly greater diameter in the mediolateral than in the superior-inferior dimension. It is situated medial to the anterior clinoid process and optic strut. The medial margin is formed by the body of the sphenoid bone. The upper margin is formed by the anterior root of the lesser wing of the sphenoid bone. The lateral margin is formed by the optic strut. The lower margin of the foramen is formed by the optic strut and the adjacent part of the body of the sphenoid bone. The optic strut blends superolaterally into the base of the anterior clinoid process and inferiorly and medially into the body of the sphenoid bone. The anterior bend of the intracavernous segment of the internal carotid artery rests against the posterior surface of the optic strut and ascends on the medial side of the anterior clinoid process. The body of the sphenoid bone contains the sphenoid sinus. The chiasmatic sulcus is a shallow groove situated on the intracranial surface of the sphenoid body between the optic canals. The tuberculum sellae is located in the midline along the posterior margin of the chiasmatic sulcus.

The superior orbital fissure provides a communication between the orbit and the middle cranial fossa (Figs. 7.1 and 7.3) (22). The cavernous sinus is situated behind and fills the posterior margin, and the contents of the orbital apex are located in front of and fill the anterior margin of the fissure. The superior orbital fissure is situated between the greater and lesser wings and body of the sphenoid bone (22). It has a somewhat triangular shape, having a wide base medially on the sphenoid body and a narrow apex situated laterally between the lesser and greater wings. The frontal bone forms a small portion of the lateral apical margin of the fissure, because the greater and lesser wings approach, but do not meet at the narrow lateral apex. The fissure slopes gently downward from its lateral to medial border. The fissure is not oriented in a strictly coronal plane, but is directed forward so that the lateral apex is slightly forward of the medial margin.

The lateral edge of the superior orbital fissure, formed by the thin edge of the greater wing, is the sharpest and best defined border. The lateral border slopes downward from its lateral to medial end. The upper half of this border is located in a more horizontal plane, and the lower half has a more vertical orientation. The junction of the upper and lower segments of the lateral edge is the site of a bony prominence that serves as the site of attachment of the lateral edge of the annular tendon, from which the four rectus muscles arise. This bony prominence can vary from narrow and pointed to broad and flat.

The superior wall of the fissure is formed by the lower surfaces of the lesser wing, the anterior clinoid process, and the adjacent part of the optic strut. The upper edge of the fissure is situated below the medial half of the sphenoid ridge. The anterior clinoid process projects backward above the junction of the narrow lateral and broader medial part of the fissure. The optic strut forms the upper medial border of the fissure. The strut forms the lateral edge of the optic foramen and the junction of the upper and medial walls of the superior orbital fissure.

The medial margin of the fissure is less sharply defined than the lateral margin. The upper part of the medial edge is formed by the lateral surface of the optic strut, and the lower part is formed by the body of the sphenoid bone. The anterior part of the carotid sulcus, the shallow groove marking the course of the intracavernous segment of the carotid artery, is situated just inside and behind the medial edge of the fissure and continues upward along the posterior margin of the optic strut and the medial side of the anterior clinoid process. The lower margin of the fissure is formed by the junction of the greater wing with the sphenoid body and is located at the level of the lower edge of the cavernous sinus and the floor of the middle fossa. The lower edge of the fissure is separated from the foramen rotundum by a narrow bridge of bone, referred to as the maxillary strut. The lower end of the superior orbital fissure is located above and blends into the medial end of the inferior orbital fissure.

The inferior orbital fissure is a narrow crevasse with long anterior and posterior borders and narrow medial and lateral ends. The long posterior edge is formed by the greater wing of the sphenoid bone. The long anterior wall is formed by the orbital surface of the maxilla, except for a short segment formed by the orbital process of the palatine bone. The narrow lateral end is formed by the zygomatic bone, and the narrow medial end is formed by the sphenoid body. The posteromedial part of the fissure communicates below with the pterygopalatine fossa and the anterolateral part communicates with the infratemporal fossa, which is located below the greater sphenoid wing. The structures passing through the fissure are the zygomatic and the infraorbital and zygomatic branches of the maxillary nerve, some branches of the internal maxillary artery, and the branches of the inferior ophthalmic vein, which communicate with the pterygoid plexus. The orbital smooth muscle spans the upper part of the fissure.

The pterygomaxillary fissure is the narrow cleft between the posterior surface of the maxilla and the anterior surface of the pterygoid process of the sphenoid bone. The pterygomaxillary fissure opens into the pterygopalatine fossa, which is located below and communicates through the medial part of the inferior orbital fissure with the orbital apex. The upper part of the pterygoid process is penetrated by the foramen rotundum, through which the maxillary nerve passes to reach the pterygopalatine fossa, where it gives rise to the infraorbital and zygomatic nerves, which course in the floor and lateral orbital wall. The ostium of the vidian canal, which transmits the vidian nerve, is located below the foramen rotundum. The medial wall of the pterygopalatine fossa is formed by the perpendicular plate of the palatine bone.

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FIGURE 7.1. A-D. Osseous relationships of the orbit. A, anterior view of the right orbit. The walls of the orbit are formed by seven bones. They are the frontal, zygomatic, sphenoid, lacrimal, ethmoid, and palatine bones, and the maxilla. The lateral border of the orbital opening is formed by the frontal process of the zygoma, except the upper part, which is formed by the zygomatic process of the frontal bone. The lower margin of the orbital opening is formed laterally by the zygoma and medially by the maxilla. The upper part of the medial border is formed by the frontal bone and the lower part is formed by the frontal process of the maxilla. The medial part of the upper border contains the frontal sinus. The superior orbital fissure is bounded above by the lesser wing of the sphenoid bone, below by the greater wing, and medially by the sphenoid body. The frontal bone forms the narrow lateral apex of the superior orbital fissure. The inferior orbital fissure is bounded posteriorly by the greater sphenoid wing and anteriorly by the maxilla. The supraorbital margin is notched or is the site of one or several small foramina that transmit the supraorbital nerves and vessels. The infraorbital groove, which transmits the infraorbital branch of the maxillary nerve, leads forward out of the inferior orbital fissure to cross the floor to reach the infraorbital canal, which ends in the infraorbital foramen. B, anterior aspect of the right optic canal. The optic canal, which transmits the optic nerve and ophthalmic artery, opens into the superomedial corner of the orbital apex. The optic canal is situated at the junction of the lesser wing with the sphenoid body. It is separated from the superior orbital fissure by the optic strut, a bridge of bone, which extends from the lower margin of the anterior clinoid to the sphenoid body. The optic strut is also referred to as the posterior root of the lesser wing. The tendinous ring, referred to as the annular tendon, from which the four rectus muscles arise, is attached to the upper, lower, and medial margin of the optic canal. The lateral edge of the annular tendon is attached to the midportion of the lateral edge of the superior orbital fissure, where a bony prominence on the greater wing marks the junction of medial and lateral parts of the fissure. C, roof of the right orbit viewed from below. The roof of the orbit is formed by the orbital plate of the frontal bone anteriorly and the lesser sphenoid wing posteriorly. The lacrimal fossa is the depression in the anterolateral part of the roof in which the lacrimal gland rests. There is another small depression on the anteromedial part of the roof that serves as the attachment for the trochlea of the superior oblique muscle. The optic foramen is situated posteriorly at the junction of the roof and medial wall. The ethmoid air cells and sphenoid sinus are located along the medial edge of the orbital roof. D, superior aspect of the floor of the anterior cranial fossae that forms the roof of both orbits. The cribriform plate of the ethmoid bone is situated in the midline between the orbital roofs. The crista galli serves as the site of attachment of the cerebral falx. Anteriorly, the frontal sinus splits into two laminae that enclose the frontal sinuses. The internal carotid artery exits the carotid canal above the foramen lacerum and passes forward in the carotid sulcus on the lateral part of the sphenoid body.

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FIGURE 7.1. E-H. Osseous relationships of the orbit. E, floor of the right orbit viewed from above. The orbital floor is formed by the orbital plate of the maxilla, the orbital surface of the zygoma, and the orbital process of the palatine bone. The orbital floor, which is very thin, forms most of the roof of the maxillary sinus. The floor is continuous with the medial wall, except in the most anterior part where the floor is perforated by the nasolacrimal canal. The anterior part of the floor is continuous with the lateral wall, but posteriorly, the floor and lateral wall are separated by the inferior orbital fissure. The infraorbital groove, which transmits the infraorbital branch of the maxillary nerve, leads forward out of the inferior orbital fissure to cross the floor to reach the infraorbital canal, which ends in the infraorbital foramen. The posterior part of the inferior orbital fissure communicates below with the pterygopalatine fossa, and the anterior part communicates with the infratemporal fossa. F, inferior aspect of the roof of the maxillary sinus, which also forms the floor of the orbit. The greater sphenoid wing forms much of the middle fossa floor and the posterior part of the lateral orbital wall. The pterygopalatine fossa is located behind the maxillary sinus and contains the terminal part of the maxillary artery, the maxillary nerve, and the pterygopalatine ganglion and some branches of all three structures. The pterygopalatine fossa opens through the pterygomaxillary fissure into the infratemporal fossa, which is located below the greater sphenoid wing and contains the pterygoid muscles, a segment of the maxillary artery, branches of the mandibular nerve and the pterygoid venous plexus. The medial wall of the pterygopalatine fossa is formed by the perpendicular plate of the palatine bone and contains an opening, the sphenopalatine foramen, that communicates with the nasal cavity. G, lateral view of the medial wall of the right orbit. The medial wall is formed by the frontal process of the maxilla, the lacrimal bone, the orbital plate of the ethmoid bone, and the sphenoid body. The medial wall is extremely thin in the area of the orbital plate of the ethmoid bone, which separates the orbit and ethmoidal sinuses. The lacrimal sac, which sits in the lacrimal groove, drains into the nasal cavity through the nasolacrimal canal. The lacrimal groove is formed by the frontal process of the maxilla anteriorly and the lacrimal bone posteriorly. The anterior and posterior ethmoidal foramina, which transmit the anterior and posterior ethmoidal branches of the ophthalmic artery and the anterior and posterior ethmoidal branches of the nasociliary nerve, pass through the frontoethmoidal suture or the adjacent part of the frontal bone and open into the anterior cranial fossa along the lateral edge of the cribriform plate. The pterygomaxillary fissure opens into the pterygopalatine fossa. H, lateral aspect of the lateral wall of the right orbit. The zygoma forms the lateral rim and the anterior part of the lateral wall of the orbit. Behind the zygoma, the lateral wall of the orbit is formed by the greater sphenoid wing. The temporal fossa is located between the zygomatic arch and the greater wing. The temporalis muscle arises in the temporal fossa and extends downward medial to the zygomatic arch to attach to the coronoid process of the mandible. The infratemporal fossa is located medial to the temporal fossa, below the greater sphenoid wing. The pterygomaxillary fissure, located between the posterior maxilla and the pterygoid process, opens into the pterygopalatine fossa.

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FIGURE 7.1. I-M. Osseous relationships of the orbit. I, intracranial aspect of the right optic canal. The intracranial end of the optic canal has an ovoid shape with a slightly greater diameter in the mediolateral than in the superoinferior dimension. It is situated medial to the anterior clinoid and optic strut. The medial margin is formed by the sphenoid body. The upper margin is formed by the anterior root of the lesser sphenoid wing. The lateral margin is formed by the optic strut, which is also referred to as the posterior root of the lesser wing. The lower margin of the foramen is formed by the optic strut and the adjacent part of the sphenoid body. J, intracranial aspect of the right superior orbital fissure. The superior orbital fissure provides a communication between the orbit and the middle fossa. It is bounded above by the lesser wing, below by the greater wing, and medially by the sphenoid body. A small portion of the lateral apex of the fissure is formed by the frontal bone. The midportion of the lateral margin of the fissure, at the junction of the fissure’s narrow lateral and larger medial part, is the site of a prominence that serves as the lateral attachment of the annular tendon. K, orbital aspect of the right inferior orbital fissure. The inferior orbital fissure has long anterior and posterior borders and narrow medial and lateral ends. The long posterior edge is formed by the greater wing. The long anterior wall is formed by the orbital surface of the maxilla, except for a short posterior segment formed by the orbital process of the palatine bone. The narrow lateral end is formed by the zygomatic bone, and the narrow medial end is formed by the sphenoid body. The posteromedial part of the fissure communicates below with the pterygopalatine fossa, and the anterolateral part communicates with the infratemporal fossa. The orbital smooth muscle spans the upper part of the fissure. L, anterior aspect of the right optic canal and an anomalous ophthalmic foramen. In this specimen there is a foramen in the optic strut, referred to as an ophthalmic foramen, that transmits the ophthalmic artery. M, anterolateral view of the right zygomaticofacial foramina. The zygomaticofacial foramina transmit the zygomaticofacial branches of the maxillary nerve. The zygomatic nerve arises from the maxillary nerve in the pterygopalatine fossa and passes through the inferior orbital fissure to course along the lateral wall of the orbit, where it divides into zygomaticofacial and zygomaticotemporal branches. The branches enter the zygomatico-orbital foramina on the orbital surface of the zygomatic bone. The zygomaticofacial branches exit the zygomaticofacial foramina to supply the cheek. The zygomaticotemporal nerve gives a branch to the lacrimal nerve as it passes along the inferolateral margin of the orbit. It enters the zygomatico-orbital foramen on the orbital surface and exits the zygomaticotemporal foramina to reach the temporal fossa above the zygomatic arch where it is distributed to the skin of the temple. The lacrimal foramen transmits a branch of the recurrent branch of the ophthalmic or lacrimal artery, which exits the orbit through the superior orbital fissure, courses laterally below the sphenoid ridge, and turns forward through the lacrimal foramen to supply the periorbita. Ant., anterior; Attach., attachment; Car., carotid; Clin., clinoid; Crib., cribriform; Depress., depression; Eth., ethmoid, \ ethmoidal; Fiss., fissure; For., foramen; Front., frontal; Gr., greater; Inf., inferior; Infraorb., infraorbital; Infratemp., infratemporal; Lac., lacrimal; Less., lesser; Mandib., mandibular; Max., maxillary; Nasolac., nasolacrimal; Ophth., ophthalmic; Orb., orbital; Palat., palatine; Perp., perpendicular; Post., posterior; Proc., process; Pteryg., pterygoid; Pterygomax., pterygomaxillary; Pterygopal., pterygopalatine; Sphen., sphenoid; Sup., superior; Supraorb., supraorbital; Troch., trochlear; Tuberc., tuberculum; Zygo., zygomatic; Zygomaticofac., zygomaticofacial; Zygomatico-orb., zygomatico-orbital.

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FIGURE 7.2. A-D. Superior view of a stepwise dissection of the neural structures in the orbit and superior orbital fissure. A, the dura has been removed from the part of the frontal and sphenoid bones forming the orbital roof. The olfactory bulb rests on the cribriform plate. B, the orbit and optic canal have been unroofed, the anterior clinoid process removed, and the periorbita opened to expose the trochlear, frontal, and lacrimal nerves coursing in the orbital fat just beneath the periorbita. The optic strut, which has been partially removed, separates the optic canal and superior orbital fissure. C, the orbital fat has been removed. The ophthalmic nerve divides into the lacrimal, frontal, and nasociliary nerves. The frontal nerve passes through the superior orbital fissure and courses on the levator muscle where it divides into a supratrochlear nerve, which passes above the trochlea of the superior oblique muscle, and the supraorbital nerve, which passes through a foramen or notch in the supraorbital margin. The lacrimal nerve passes above the lateral rectus muscle to innervate the lacrimal gland and convey sensation to the area around the lateral part of the supraorbital margin. The trochlear nerve passes medially above the levator muscle to reach the superior oblique muscle. The nasociliary branch of the ophthalmic nerve passes between the superior rectus muscle and the optic nerve to reach the medial side of the orbit. The tendon of the superior oblique muscle passes through the trochlea and below the superior rectus muscle to insert on the globe between the attachment of the superior and lateral rectus muscles. D, the frontal nerve and the levator and superior rectus muscles have been divided and reflected. This exposes the superior ophthalmic vein, ophthalmic artery, and nasociliary nerve as they pass above the optic nerve. The dura lining the middle cranial fossa has been removed to expose the oculomotor, trochlear, and ophthalmic nerves as they course in the lateral wall of the cavernous sinus, and the maxillary and mandibular nerves in the middle fossa. The trochlear nerve passes forward in the wall of the cavernous sinus between the oculomotor and ophthalmic nerves and turns medially at the level of the superior orbital fissure to pass above the levator muscle. The optic nerve and ophthalmic artery pass through the optic canal and the medial part of the annular tendon. The trochlear, lacrimal, and frontal nerves and the superior ophthalmic vein pass through the narrow lateral part of the superior orbital fissure above and outside the annular tendon. The superior and inferior divisions of the oculomotor nerve, and the nasociliary and abducens nerves pass through the larger medial part of the superior orbital fissure and the annular tendon.

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FIGURE 7.2. E-F. Superior view of a stepwise dissection of the neural structures in the orbit and superior orbital fissure. E, the annular tendon has been divided in the interval between the origin of the superior and lateral rectus muscles. The oculomotor, abducens, and nasociliary nerves pass through the superior orbital fissure and annular tendon. The oculomotor nerve splits into superior and inferior divisions. The superior division branches on the lower surface of the superior rectus and sends branches along the medial margin of the superior rectus muscle to enter the levator muscle. The fibers of the inferior division give rise to three branches. One passes below the optic nerve to supply the medial rectus muscle, another enters the superior surface of the inferior rectus muscle, and the third branch courses along the lateral margin of the inferior rectus muscle to innervate the inferior oblique muscle. The branch to the inferior oblique muscle gives rise to the motor (parasympathetic) root to the ciliary ganglion. The nasociliary nerve arises from the medial surface of the ophthalmic nerve and gives rise to the sensory root of the ciliary ganglion. Short ciliary nerves arise from the ciliary ganglion and enter the globe around the optic nerve. The abducens nerve courses on the medial side of the ophthalmic nerve in the cavernous sinus, but it passes below the ophthalmic nerve in the superior orbital fissure to enter the medial surface of the lateral rectus muscle. F, a segment of the orbital portion of the optic nerve has been removed. This exposes the branch of the inferior division of the oculomotor nerve, which passes below the optic nerve and enters the medial rectus muscle. The short ciliary nerves arise from the ciliary ganglion and enter the globe around the margin of the optic nerve. A., artery; Ant., anterior; Car., carotid; Cav., cavernous; Cil., ciliary; Clin., clinoid; CN, cranial nerve; Div., division; Eth., ethmoidal; Falc., falciform; Front., frontal; Gang., ganglion; Inf., inferior; Infratroch., infratrochlear; Lac., lacrimal; Lat., lateral; Less., lesser; Lev., levator; Lig., ligament; M., muscle; Med., medial; N., nerve; Nasocil., nasociliary; Obl., oblique; Olf., olfactory; Ophth., ophthalmic; Rec., rectus; Sup., superior; Supraorb., supraorbital; Sup. Troch., supratrochlear; Tent., tentorial; Troch., trochlear; V., vein.

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FIGURE 7.3. Left lateral view of a stepwise dissection of the superior orbital fissure and adjacent part of the cavernous sinus and orbit. A, the dura covering Meckel’s cave and cavernous sinus has been removed. The cavernous sinus is located medial to the upper third of the gasserian ganglion and extends down to the lower margin of the ophthalmic nerve. The superior ophthalmic vein exits the orbit and passes below the ophthalmic nerve to enter the anterior part of the cavernous sinus. The superior petrosal sinus passes above the porus of Meckel’s cave to join the posterior part of the cavernous sinus. The superior orbital fissure is filled on its posterior side by the cavernous sinus and on its anterior margin by the fat in the orbital apex. B, the anterior clinoid, lateral orbital wall, and roof have been removed. The optic strut separates the optic nerve in the optic canal from the nerves passing through the superior orbital fissure. The superior ophthalmic vein can be seen through the periorbita as it exits the muscle cone to pass along the lateral margin of the superior orbital fissure and below the ophthalmic nerve to enter the anterior part of the cavernous sinus. C, the orbital fat has been removed to expose the nerve passing through the superior orbital fissure and the annular tendon from which the rectus muscles arise. The trochlear nerve passes medially above the oculomotor and ophthalmic nerves to reach the superior oblique muscles. The frontal, lacrimal, and trochlear nerves pass outside the annular tendon, and the nasociliary, oculomotor, and abducens nerves pass through the tendon. D, the frontal and lacrimal nerves have been depressed to show the nasociliary nerve arising from the medial side of the ophthalmic nerve. The oculomotor foramen is the portion of the opening in the annular tendon lateral to the optic foramen through which the superior and inferior divisions of the oculomotor nerve and the nasociliary nerve and abducens nerve pass. The oculomotor nerve divides into superior and inferior divisions just behind the superior orbital fissure. The abducens nerve courses on the medial side of the ophthalmic nerve in the cavernous sinus, but in the fissure, it turns laterally below the nerve to enter the medial side of the lateral rectus muscle. E, enlarged view of the oculomotor foramen. F, the annular tendon has been divided between the origin of the superior and lateral rectus muscles. The abducens nerve enters the medial aspect of the lateral rectus muscle. The superior division of the oculomotor nerve passes upward to innervate the levator and superior rectus muscles. The inferior division innervates the inferior oblique, inferior rectus, and medial rectus muscles and gives rise to the motor parasympathetic pupilloconstrictor fibers to the ciliary ganglion. A., artery; Ant., anterior; Bas., basilar; Car., carotid; Cav., cavernous; Clin., clinoid; CN, cranial nerve; Div., division; Fiss., fissure; For., foramen; Front., frontal; Inf., inferior; Lac., lacrimal; Lat., lateral; M., muscle; N., nerve; Nasocil., nasociliary; Oculom., oculomotor; Olf., olfactory; Ophth., ophthalmic; Orb., orbital; Pet., petrosal; Plex., plexus; Rec., rectus; Seg., segment; S.C.A., superior cerebellar artery; Sup., superior; V., vein.

Periorbita, Dura, and Annular Tendon

At the superior orbital fissure, the dura covering the middle fossa and cavernous sinus blends into the periorbita of the orbital apex and into the annular tendon from which the rectus muscles arise (Figs. 7.3 and 7.4). The annular tendon surrounds the orbital end of the optic foramen and the adjacent part of the superior orbital fissure. The fibrous components, which blend together to form the annular tendon, are the periorbita covering the orbital apex, the dura lining the superior orbital fissure and optic canal, and the optic sheath. The annular tendon is attached along the upper, medial, and lower margins of the optic canal, and to a bony prominence at the midportion of the lateral edge of the superior orbital fissure, at the junction of the fissure’s narrow lateral and larger medial parts. The annular tendon does not surround the whole superior orbital fissure, but encompasses only the upper-medial portion, which is situated lateral to the optic strut and optic foramen. The lower portion of the annular tendon, the site of origin of the inferior rectus muscle, extends horizontally from the sphenoid body below the optic strut and optic foramen to an attachment on the lateral edge of the fissure. From its attachment to the greater wing, the annular tendon is directed upward to blend into the periorbita and dura, which meet on the lower margin of the lesser sphenoid wing. The segment of the annular tendon passing from the greater to the lesser wing separates the narrow lateral part of the fissure from the larger medial part and serves as the site of origin of the lateral rectus muscle.

The annular tendon and the connective tissue layer extending backward divide the superior orbital fissure into three sectors: lateral, central, and inferior. The lateral sector is quite narrow, being bounded above by the lesser wing of the sphenoid bone, below by the part of the greater wing lateral to the site of attachment of the annular tendon, and medially by the annular tendon and the origin of the lateral rectus muscle. The lateral sector transmits the trochlear, frontal, and lacrimal nerves, all of which pass through the fissure outside the annular tendon. The lacrimal nerve occupies the most lateral part of the fissure, the frontal nerve is more medial. The trochlear nerve passes through the fissure on the superomedial margin of the frontal nerve. The superior ophthalmic vein also passes through this sector by coursing along the lower side of the lacrimal and frontal nerves to reach the cavernous sinus.

The central sector of the superior orbital fissure, referred to as the oculomotor foramen because it is the part of the fissure through which the oculomotor nerve passes, is bounded above by the annular tendon and adjacent part of the lesser wing, medially by the optic strut and sphenoid body, laterally by the annular tendon and the prominence on the lateral margin of the fissure to which the annular tendon attaches, and below by the segment of the annular tendon spanning the interval between the sphenoid body and the bony prominence on the lateral edge of the fissure. The inferior rectus muscle arises from the annular tendon at the lower margin of this sector. The oculomotor, nasociliary, and abducens nerves and the sensory and sympathetic roots of the ciliary ganglion pass through this sector. The optic nerve and ophthalmic artery pass medially to the oculomotor foramen through the part of the annular tendon attached to the upper, lower, and medial margins of the optic foramen. The connective tissue membrane, which extends posteriorly from the annular tendon, separates the nerves passing through the lateral and central sectors of the fissure. This connective tissue extends backward from the annulus between the frontal branch of the ophthalmic nerve, which passes through the lateral sector outside the annular tendon, and the nasociliary nerve, which passes through the central sector and the annular tendon.

The inferior sector of the superior orbital fissure is situated below the annular tendon. It is bounded below by the junction of the body and greater wing of the sphenoid bone, above by the annular tendon, laterally by the part of the greater wing below the attachment of the annular tendon, and medially by the sphenoid body. The inferior rectus muscle arises from the annular tendon at the upper margin of this sector. Orbital fat extends backward below the inferior rectus muscle into this part of the fissure. The lower margin of this sector contains a posterior extension of the orbital smooth muscle, which spans the upper margin of the inferior orbital fissure. The orbital fat extends backward between the inferior rectus muscle and the orbital smooth muscle and medial to the segment of the abducens and nasociliary nerves passing through the fissure. Removal of this fat exposes the fine branches of the carotid sympathetic plexus entering the orbit, some of which form the sympathetic root of the ciliary ganglion.

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FIGURE 7.4. A-D. A, coronal section of orbits and cranial base anterior to the orbital apex. The floor of the orbit faces the maxillary sinus and the medial wall faces the ethmoid air cells. The inferior concha is a separate bone attached to the medial maxillary wall. The middle turbinate, an appendage of the ethmoid bone, attaches to the lateral nasal wall at the level of the roof of the maxillary sinus. B, enlarged view of right side shown in A. The ophthalmic artery enters the orbit on the lateral side of the optic nerve and crosses medially above the nerve. The abducens nerve enters the medial surface of the lateral rectus muscle. The optic nerve is enclosed in the optic sheath. The nerve to the inferior oblique muscle courses along the lateral edge of the inferior rectus muscle. C, anterosuperior view showing the relationship of the orbital apex to the optic strut, optic canal, and superior orbital fissure. The optic strut, which has been removed, separates the optic nerve in the optic canal from the superior orbital fissure. The optic nerve enters the orbit on the medial side of the optic strut and the oculomotor, trochlear, abducens, and ophthalmic nerves enter the orbit on the lateral side of the strut. The rectus muscles arise from the annular tendon, which encircles the optic canal and the central part of the superior orbital fissure. The anterior clinoid process has been removed to expose the clinoid segment of the internal carotid artery. The upper dural ring surrounds the carotid artery at the upper edge of the clinoid segment. D, cross section of right orbit just in front of the apex. The ophthalmic artery enters the orbit on the lateral side of the optic nerve. The branch of the inferior division of the oculomotor nerve to the medial rectus muscle passes below the optic nerve.

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FIGURE 7.4. E-H. E, superior view of the floor of both orbits. The roof of the maxillary sinus forms the orbital floors. The infraorbital and zygomatic branches of the maxillary nerve enter the orbit by passing through the inferior orbital fissure. The zygomatic nerve courses along the lateral wall of the orbit to give rise to the zygomaticofacial and zygomaticotemporal nerves, which innervate the skin over the malar eminence and temporal region, respectively. The infraorbital nerve and artery course along the floor of the orbit to reach the cheek. F, enlarged view of the right orbit showing the course along the orbital walls taken by the zygomaticofacial, zygomaticotemporal, and infraorbital nerves. The zygomaticofacial nerves pierce the lateral orbital rim to reach the malar eminence and the zygomaticotemporal branches pass upward to reach the temple. G, anterior view of both orbits in another specimen. A portion of the floor of both orbits has been removed to expose the maxillary sinus while preserving the infraorbital and zygomatic nerves. The rectus muscles arise in the orbital apex from the annular tendon, which surrounds the optic canal and adjacent part of the superior orbital fissure. The ethmoidal sinuses are located on the medial side of the orbit. H, enlarged view. Some of the posterior wall of the maxillary sinus has been removed to expose the pterygopalatine fossa and the origin of the infraorbital and zygomatic nerves from the maxillary nerve. The structures in the pterygopalatine fossa are the maxillary nerve and its terminal branches, the pterygopalatine ganglion, and the terminal branches of the maxillary artery. The maxillary nerve gives rise to communicating rami to the pterygopalatine ganglion. A., artery; A.C.A., anterior cerebral artery; Car., carotid; Cav., cavernous; Clin., clinoid; CN, cranial nerve; Eth., ethmoid; Fiss., fissure; Front., frontal; Gang., ganglion; Inf., inferior; Infraorb., infraorbital; Lac., lacrimal; Lat., lateral; Lev., levator; M., muscle; Max., maxillary; M.C.A., middle cerebral artery; Med., medial; Mid., middle; N., nerve; Nasocil., nasociliary; Obl., oblique; Ophth., ophthalmic; Orb., orbital; Pterygopal., pterygopalatine; Rec., rectus; Seg., segment; Sup., superior; Temp., temporal; Zygo., zygomatic; Zygomaticofac., zygomaticofacial.

Neural Relationships

Optic Nerve

The optic nerve is divided into four parts: intraocular, intraorbital, intracanalicular, and intracranial (Figs. 7.2–7.5). The intracanalicular part, located in the optic canal, and the intraorbital portions of the optic nerve are surrounded by dura and arachnoid. The subarachnoid space surrounding the intracranial part of the nerve extends forward from and communicates with the subarachnoid space around the intracanalicular and intraorbital portions of the nerve. The optic nerve passes through the medial part of the annular tendon and below the levator and superior rectus muscles. The dural sheath around the optic nerve blends smoothly into the periorbita at the anterior end of the optic canal. After passing through the optic canal, which forms a prominence in the upper part of the sphenoid sinus immediately in front of the sella turcica and along the medial aspect of the anterior clinoid process, the intracranial portion of the nerve is directed posterior, superiorly, and medially toward the optic chiasm.

The intraocular portion of the optic nerve, which includes the optic disc, lies within the sclera. The intraorbital portion of the optic nerve is surrounded by orbital fat and follows a slightly tortuous course. The ciliary nerves and arteries pierce the sclera in the area around the optic nerve. The ophthalmic artery enters the orbit on the lateral side of the nerve and passes above the nerve to reach the medial sides of the orbit. The superior ophthalmic vein arises in the anteromedial part of the orbit and crosses above the nerve to reach the orbital apex. Both the artery and vein course between the superior rectus muscle and the optic nerve. The branch of the inferior division of the oculomotor nerve to the medial rectus muscle passes below the optic nerve at about the same level that the ophthalmic artery and nasociliary nerve pass above the optic nerve.

Oculomotor, Trochlear, and Abducens Nerves

The oculomotor nerve enters the orbit by passing through the medial part of the fissure on the lateral surface of the optic strut (Fig. 7.3). At the level of the posterior margin of the fissure, in the area medial to the trochlear and nasociliary nerves, the oculomotor nerve splits into superior and inferior divisions that course one above the other as they pass through the central sector of the fissure and the oculomotor foramen on the medial side of the branches of the ophthalmic nerve. The superior division of the oculomotor nerve enters the orbit below the attachment of the superior rectus muscle to the annular tendon and sends its branches upward lateral to the optic nerve to reach the lower surface of the superior rectus and levator muscles. The inferior division courses inferiorly and medially as it proceeds through the fissure on the medial side of the nasociliary and abducens nerves. At the orbital apex, it splits into three individual branches: two are directed forward to reach the inferior rectus and inferior oblique muscles, and one passes medially below the optic nerve to enter the medial rectus muscle. In addition, the branch to the inferior oblique muscle gives rise to the motor (parasympathetic) root to the ciliary ganglion. The parasympathetic fibers synapse in the ciliary ganglion, which gives rise to the short ciliary nerves that pierce the sclera to reach the ciliary body and iris.

The trochlear nerve courses in the lateral wall of the cavernous sinus below the oculomotor nerve and above the ophthalmic nerve. It passes through the upper edge of the narrow lateral part of the superior orbital fissure outside the annular tendon and passes medially above the frontal nerve and the levator muscle to reach the superior oblique muscle.

The abducens nerve travels forward in the cavernous sinus on the medial side of the ophthalmic nerve and shifts laterally below the nasociliary nerve as it passes through the superior orbital fissure and annular tendon to enter the medial surface of the lateral rectus muscle. At the apex of the orbit, the nasociliary nerve and the inferior division of the oculomotor nerve curve medially as the abducens nerve shifts laterally to enter the medial surface of the lateral rectus muscle. Some fibers of the carotid sympathetic plexus pass to and course within the abducens nerve in the cavernous sinus.

Trigeminal Nerve

The ophthalmic branch of the trigeminal nerve is the smallest of the three trigeminal divisions (Figs. 7.2 and 7.3). It is inclined upward as it passes forward near the medial surface of the dura forming the lower part of the lateral wall of the cavernous sinus to reach the superior orbital fissure. It is flattened in the wall of the cavernous sinus, but at the superior orbital fissure, it takes on an oval configuration. The ophthalmic nerve splits into the lacrimal, frontal, and nasociliary nerves as it approaches the superior orbital fissure.

The lacrimal nerve arises at the level of or just behind the superior orbital fissure from the lateral edge of the ophthalmic nerve and passes through the lateral edge of the fissure on the lateral side of the frontal nerve and above the superior ophthalmic vein. On entering the orbit, the lacrimal nerve courses along the superior margin of the lateral rectus muscles, where it receives secretory fibers conveyed initially in the zygomatic nerve from the pterygopalatine ganglion and distributed through the lacrimal nerve to the lacrimal gland. The lacrimal nerve conveys sensation from the area in front of the lacrimal gland.

The remainder of the ophthalmic nerve splits into the frontal nerve, which passes through the lateral sector of the fissure, and the nasociliary nerve, which passes through the central sector on the medial side of the origin of the lateral rectus muscle from the annular tendon. The frontal branch of the ophthalmic nerve arises in the lateral wall of the cavernous sinus and passes through the narrow lateral part of the superior orbital fissure on the medial side of the lacrimal nerve and superior ophthalmic vein and below the trochlear nerve. The frontal nerve courses outside and superolateral to the annular tendon and divides into the supratrochlear and supraorbital nerves within the orbit. The supratrochlear nerve runs anteriorly above the trochlea of the superior oblique muscle with the supratrochlear artery. The supraorbital nerve courses above the levator muscle with the supraorbital artery. It conveys sensation from the upper eyelid and forehead and may also carry some sympathetic fibers to the globe and pupillary dilator.

The nasociliary nerve arises from the medial side of the ophthalmic nerve and is situated above and lateral to the abducens nerve in the anterior part of the cavernous sinus. Both the abducens and the nasociliary nerves course medial to the part of the ophthalmic nerve from which the lacrimal and frontal nerves arise. At the level of the fissure, the nasociliary nerve gently ascends laterally to the inferior division of the oculomotor nerve and then crosses medially between the two divisions of the oculomotor nerve and above the optic nerve to reach the medial part of the orbit, where it gives rise to the anterior and posterior ethmoidal and infratrochlear nerves. The sensory root of the ciliary ganglion arises from the lower edge of the nasociliary nerve during passage through the lateral wall of the cavernous sinus or within the fissure. The sensory root may infrequently arise as far forward as the anterior margin of the fissure. Within the fissure, it courses between the abducens nerve laterally and the inferior oculomotor division medially and passes forward to join the posterior edge of the ciliary ganglion. The fibers from the sensory root are distributed to the globe with the short ciliary nerves and convey sensation from the cornea and globe. The nasociliary nerve also gives rise to the long ciliary nerves that enter the sclera around the optic nerve with the short ciliary nerves. The long ciliary nerve conveys sympathetic fibers to the globe and pupillary dilator and may also carry some sensation from the globe and cornea.

The maxillary nerve passes through the foramen rotundum to enter the pterygopalatine fossa, where it gives rise the infraorbital and zygomatic nerves and communicating rami to the sphenopalatine ganglion. The infraorbital and zygomatic branches pass through the inferior orbital fissure to course within the orbit. The infraorbital nerve courses along the orbital floor in the infraorbital groove and canal to reach the infraorbital foramen, where its branches are distributed to the cheek. The zygomatic branch passes through the inferior orbital fissure and courses just inside the lateral wall of the orbit, where it divides into zygomaticofacial and zygomaticotemporal branches. These branches enter the zygomatico-orbital foramina on the intraorbital surface of the zygoma and exit the zygoma at the zygomaticofacial and zygomaticotemporal foramina to reach the skin of the cheek and temple, respectively.

Ciliary Ganglion

The ciliary ganglion is situated on the inferolateral aspect of the optic nerve and on the medial side of the lateral rectus muscle (Figs. 7.2 and 7.5). It receives three branches: the motor (parasympathetic) root from the inferior division of the oculomotor nerve, the sensory root from the nasociliary nerve, and sympathetic fibers from the plexus around the internal carotid artery. The sympathetic fibers sometimes blend with the sensory root in the orbit. The parasympathetic fibers synapse in the ciliary ganglion. The sympathetic fibers arise in the cervical sympathetic ganglia and pass through the ciliary ganglion without synapsing. The short ciliary nerves pass from the ganglion to the globe.

Sympathetic Fibers

Sympathetic fibers ascend on the surface of the internal carotid artery, pass through the medial part of the superior orbital fissure and the oculomotor foramen, and course with the abducens and ophthalmic nerves in the cavernous sinus and also with the ophthalmic artery. Some of these fibers collect together to form the sympathetic root of the ciliary ganglion, which courses as an independent branch surrounded by orbital fat. The fibers forming the sympathetic root run forward and upward along the medial margin of the abducens nerve to reach the area lateral to the inferior division of the oculomotor nerve, where they pass through the central sector of the superior orbital fissure. Some sympathetic fibers join the ophthalmic division and are distributed to the pupil in the long ciliary and sensory root of the ciliary ganglion, both of which arise from the nasociliary nerve. Others pass directly through the fissure and orbit to the globe. Some sympathetic fibers from the carotid plexus accompany the ophthalmic artery.

Vidian Nerve and Pterygopalatine Ganglion

The vidian nerve, formed by the union of the greater petrosal branch of the facial nerve and the deep petrosal nerve from the carotid plexus, exits the vidian canal and enters the posterior aspect of the sphenopalatine ganglion in the pterygopalatine fossa. Parasympathetic fibers are conveyed in the greater petrosal nerve and sympathetic fibers are conveyed in the deep petrosal nerve. Communicating branches, typically two in number, arise from the inferior portion of the maxillary nerve and descend to join the sphenopalatine ganglion, which is located anterior to the aperture of the vidian canal. The parasympathetic fibers synapse in the ganglion and the sympathetic fibers pass through the ganglion without synapse. Fibers exiting the ganglion join the nasal, nasopalatine, and palatine nerves to convey secretory impulses to the nasal and palatine glands. The secretory fibers to the lacrimal gland pass from the ganglion via the maxillary nerve to join the zygomatic nerve, which sends a communication to the gland via the lacrimal nerve. In addition, sensory fibers, which pass through the pterygopalatine ganglion, reach the maxillary nerve and convey sensation from the ethmoidal and sphenoid sinuses, nasal cavity, nasal septum, hard palate, and roof of the pharynx.

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FIGURE 7.5. A-D. A, the orbital part of the orbicularis oculi muscle has been removed and the palpebral part preserved. The supraorbital nerves carry sensation from the skin of the forehead and the infraorbital nerve carries sensation from the cheek, upper lip, and adjacent part of the nose. The supraorbital nerves reach the skin of the forehead by passing through a notch or foramen in the superior orbital rim. The infraorbital nerve arises from the maxillary nerve and passes through the inferior orbital fissure and along the infraorbital groove and canal in the orbital floor to reach the infraorbital foramen. B–H, anterior views of cross sections of the orbit at progressively deeper levels. B, anterior aspect of a coronal section through the right orbit just posterior to the globe and the inferior oblique muscle. The intraorbital part of the optic sheath, an anterior extension of the dura lining the optic canal, surrounds the optic nerve. At this level, the ophthalmic artery has crossed from lateral to medial and the superior ophthalmic has crossed from medial to lateral above the optic nerve. C, enlarged view of B to show the relationship of the cisternal and canalicular segments of the optic nerve to the intraorbital part. The cisternal segment of the optic nerve courses medial to the supraclinoid segment of the internal carotid artery. The optic sheath surrounds the intracanalicular segment in the optic canal. The optic sheath and the periorbita fuse at the orbital apex to form the annular tendon from which the rectus muscles arise. Fibers from the superior division of the oculomotor nerve enter the lower surface of the levator and superior rectus muscles. The sphenoid sinus and sella are on the medial side of the optic canal. D, the orbital fat has been removed and the lateral rectus muscle has been reflected to expose the ciliary ganglion, which is located inferolateral to the optic nerve. The inferior division of the oculomotor nerve sends individual branches to the inferior and medial rectus and the inferior oblique muscles. The ciliary ganglion has sensory, parasympathetic, and sympathetic roots. The motor (parasympathetic) root of the ciliary ganglion arises from the branch of the inferior oculomotor division to the inferior oblique muscle. Sensory fibers from the globe pass through the short ciliary nerves to reach the ciliary ganglion, where they form the sensory root of the ciliary ganglion, which joins the nasociliary branch of the ophthalmic nerve. Sympathetic fibers reach the ciliary ganglion from the carotid plexus. The ciliary ganglion gives rise to numerous short ciliary nerves that pierce the sclera and terminate in the pupillary sphincter and ciliary muscle.

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FIGURE 7.5. E-H. E, anterior aspect of a coronal section at the level of the ciliary ganglion. The inferior division of the oculomotor nerve splits into three branches that innervate the inferior and medial rectus and inferior oblique muscles. The nasociliary branch of the ophthalmic nerve passes through the annular tendon, and the frontal and lacrimal branches pass outside the annular tendon through the lateral part of the superior orbital fissure. The nasociliary nerve and ophthalmic artery course above the optic nerve at this level. F, section located just anterior to the lateral end of superior orbital fissure at the level of the posterior ethmoidal canal. At this level, the ophthalmic artery courses on the lateral side of the optic nerve and the nasociliary nerve courses between the optic nerve and ophthalmic artery. The recurrent meningeal artery passes above the ophthalmic artery. The orbital smooth muscle spans the inferior orbital fissure. G, enlarged view of the section shown in F after removal of the orbital fat. At this level, the oculomotor nerve has split into a superior division that supplies the superior rectus and levator muscles and an inferior division that innervates the inferior rectus, medial rectus, and inferior oblique muscles. The central retinal artery arises from the ophthalmic artery and courses below the optic nerve. The superior ophthalmic vein exits the intraconal area by passing between the heads of the superior and lateral rectus muscles, and the inferior ophthalmic vein passes between the heads of the lateral and inferior rectus muscles. H, section through the orbital apex immediately in front of the superior orbital fissure. The annular tendon is divided into medial and lateral parts. The medial part is located in front of the optic canal and the lateral part is situated in front of the superomedial part of the superior orbital fissure. The optic nerve and ophthalmic artery pass through the medial part. The superior and inferior divisions of the oculomotor nerve and the abducens and nasociliary nerves and the sensory root of the ciliary ganglion pass through the lateral part. The superior ophthalmic vein and the recurrent meningeal artery course between the superior and lateral rectus muscles and exit the superior orbital fissure by passing outside the annulus. The inferior ophthalmic vein has exited the intraconal area at this level and is coursing below the lateral rectus muscle on its way to the cavernous sinus. This section crosses the inferior division of the oculomotor nerve proximal to its subdivision into individual branches. A., artery; Car., carotid; Cent., central; Cil., ciliary; CN, cranial nerve; Div., division; Falc., falciform; Front., frontal; Gang., ganglion; Inf., inferior; Infraorb., infraorbital; Lac., lacrimal; Lat., lateral; Lev., levator; Lig., ligament; M., muscle; Med., medial; Men., meningeal; N., nerve; Nasocil., nasociliary; Obl., oblique; Ophth., ophthalmic; Orbic., orbicularis; Rec., rectus, recurrent; Ret., retinal; Sphen., sphenoid; Sup., superior; Supraorb., supraorbital; V., vein.

Arterial Relationships

Internal Carotid Artery

The anterior bend of the intracavernous segment of the internal carotid artery courses along the posterior edge of the medial margin of the superior orbital fissure and rests against the posterior surface of the optic strut (Figs. 7.3–7.5). After ascending along the posterior margin of the optic strut, the artery turns upward along the medial margin of the anterior clinoid process to reach the subarachnoid space. The segment of the artery coursing along the medial margin of the clinoid process is referred to as the clinoid segment.

Ophthalmic Artery

The ophthalmic artery usually arises just above the cavernous sinus from the medial half of the superior aspect of the anterior bend of the internal carotid artery (Figs. 7.6 and 7.7). Its origin is located under the medial part of the optic nerve, just behind the optic canal. In the optic canal, the ophthalmic artery courses within the optic sheath below the optic nerve and through the annular tendon. It exits the optic canal and penetrates the optic sheath to enter the orbital apex on the inferolateral aspect of the optic nerve. In the optic canal, the ophthalmic artery sometimes gives a recurrent branch to the intracranial segment of the optic nerve. Approximately 8% of ophthalmic arteries arise in the cavernous sinus rather than in the subarachnoid space (5). Those ophthalmic arteries arising in the cavernous sinus pass through the superior orbital fissure, rather than the optic canal, to reach the orbit. In some cases in which the larger ophthalmic artery passes through the superior orbital fissure, a second, smaller or hypoplastic ophthalmic artery may arise in the supraclinoid area and course in the usual manner through the optic foramen to reach the orbit. In other cases, with a normal-sized ophthalmic artery passing through the optic foramen, a smaller artery that arises from the intracavernous carotid may pass through the fissure, usually supplying the territory normally supplied by the lacrimal artery.

The ophthalmic artery may also arise as duplicate arteries of nearly equal size (24). The upper duplicate artery usually arises from the supraclinoid portion of the internal carotid artery and passes through the optic canal to enter the orbital apex on the lateral side of the optic nerve (Fig. 7.6). The lower duplicate artery usually arises from the internal carotid artery in the cavernous sinus and passes through the superior orbital fissure between the oculomotor nerve laterally and the abducens and ophthalmic nerves medially. Both usually cross the optic nerve, one above and one below, to reach the medial part of the orbit. The ophthalmic artery may infrequently arise from the clinoid segment, in which case it passes through the superior orbital fissure to reach the orbit (Fig. 7.6A). A few will pass through an accessory foramen, called the ophthalmic foramen, which pierces the optic strut (Fig. 7.1L). It may also infrequently arise as a branch of the middle meningeal artery (Fig. 7.8) (15).

The ophthalmic artery, after passing through the optic foramen and annular tendon and reaching the lateral aspect of the optic nerve may give rise to a recurrent meningeal artery that passes backward through the superior orbital fissure to reach the dura. The ophthalmic artery passes above the optic nerve in approximately 85% of orbits. In the remainder, it passes below the nerve. After passing the optic nerve, the artery courses between the superior oblique and the medial rectus muscles, where it gives rise to the anterior and posterior ethmoidal arteries that pass through the anterior and posterior ethmoidal canals with the anterior and posterior ethmoidal nerves.

The ophthalmic artery gives rise to the central retinal, lacrimal, long and short ciliary, supraorbital, medial palpebral, infratrochlear, supratrochlear, and dorsal nasal arteries, plus muscular branches to the extraocular muscles and meningeal branches that pass through the ethmoidal or lacrimal foramina or superior orbital fissure to reach the meninges. The palpebral branches of the ophthalmic artery plus the supratrochlear, infratrochlear, supraorbital, dorsal nasal, and lacrimal branches supply the skin and soft tissues of the eyelids and area around the orbital rim.

The central retinal artery, which is the first and one of the smallest branches of the ophthalmic artery, arises medial to the ciliary ganglion, pierces the lower surface of the nerve, and courses a short distance inside the dural sheath of the nerve before passing to the center of the nerve and forward to the retina in the center of the nerve. The central retinal artery is a terminal branch without anastomotic connections (Fig. 7.7). Its loss results in blindness.

The lacrimal artery, one of the largest and earliest branches of the ophthalmic artery, accompanies the lacrimal nerve and is distributed to the lacrimal gland and the lateral part of the eyelids and conjunctiva. A recurrent branch may also arise from the lacrimal artery or adjacent part of the ophthalmic artery and pass through the superior orbital fissure to reach the dura, only to return to the periorbita by passing through the lacrimal foramen located lateral to the superior orbital fissure on the greater sphenoid wing. The supraorbital artery arises from the ophthalmic artery as it crosses the optic nerve and runs along the medial side of the levator and superior rectus muscles to course with the supraorbital nerves. The supratrochlear artery courses with the supratrochlear nerve. The short and long posterior ciliary arteries arise from the ophthalmic artery, course with the short and long ciliary nerves, pierce the sclera around the optic nerve, and supply the choroidal coat and ciliary processes. The anterior ciliary arteries are derived from the branches to the extraocular muscles and run to the front of the globe with the tendons of the extraocular muscles, where they pierce the sclera and end in the greater arterial circle of the iris.

The anterior and posterior ethmoidal branches of the ophthalmic artery, of which the anterior is the larger, arise beneath the superior oblique muscle and pass through the anterior and posterior ethmoidal canal to reach the dura beside the cribriform plate (Figs. 7.2 and 7.7). The anterior ethmoidal artery crosses near the anterior edge of the cribriform plate. The posterior ethmoidal artery crosses near the posterior edge of the cribriform plate a few millimeters anterior to the orbital end of the optic canal. As the anterior ethmoidal artery passes across the floor of the anterior cranial fossa near the cribriform plate, it gives rise to the anterior falx artery, which runs between and supplies the anterior portion of the falx and walls of the superior sagittal sinus. The anterior and posterior ethmoidal arteries then pass through the cribriform plate area to supply the ethmoidal sinuses, the infundibulum of the frontal sinus, the anterior nasal cavity, and the skin over the cartilaginous part of the nose.

Arteries that supply the margins of the superior orbital fissure and may be recruited to supply tumors in the region include the anterior branch of the middle meningeal artery, the recurrent meningeal branches of the ophthalmic and lacrimal arteries, the meningeal branches of the internal carotid artery, the tentorial branch of the meningohypophyseal trunk, the anterior branch of the inferolateral trunk, and the terminal branches of the internal maxillary artery.

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FIGURE 7.6. Anomalies of the ophthalmic artery. A, right ophthalmic artery origin from the clinoid segment of the internal carotid artery. The ophthalmic artery usually arises just above the clinoid segment, but in this case, the artery arises from the clinoid segment below the anterior clinoid process, which has been removed. The artery passes through the superior orbital fissure between the oculomotor and ophthalmic nerves. The lateral wall of the right cavernous sinus and the anterior clinoid process have been removed to expose the intracavernous and clinoid segments of the internal carotid artery, and the ophthalmic nerve has been retracted to expose the inferolateral trunk. B, ophthalmic artery origin in the cavernous sinus. Lateral aspect of a right ophthalmic artery that arises from the intracavernous segment of the left internal carotid artery. The upper half of a segment of the ophthalmic nerve has been removed to expose an ophthalmic artery. The anterior clinoid artery has been removed to expose the clinoid segment in the interval between the optic and oculomotor nerves. C, the medial rectus muscle has been divided near the globe and reflected posteriorly to expose an ophthalmic artery that courses below the optic nerve to reach the medial part of the orbit, as occurs in approximately 15% of orbits. The branch of the inferior division of the oculomotor nerve to the medial rectus muscle enters the medial side of the muscle. The anterior ethmoidal artery courses below the superior oblique muscle to reach the anterior ethmoidal canal. D and E, duplicate left ophthalmic  arteries. D, superior aspect of a duplicate ophthalmic artery. The levator and superior rectus muscles have been reflected medially and the lateral rectus muscle has been reflected laterally to expose the left optic nerve and the duplicate arteries. The upper duplicate artery arises from the supraclinoid segment of the internal carotid artery, passes through the optic canal to enter the orbital apex on the lateral side of the optic nerve, and courses below the optic nerve to reach the medial part of the orbit. The lower duplicate artery arises from the internal carotid artery in the cavernous sinus, passes through the superior orbital fissure on the lateral side of the optic nerve, and crosses above the nerve to reach the medial part of the orbit. E, lateral view. The annular tendon has been opened between the superior and lateral rectus muscles. The duplicate artery arising above the cavernous sinus passes forward and downward to course below the optic nerve. The duplicate artery arising in the cavernous sinus passes above the optic nerve. A., artery; Ant., anterior; Car., carotid; Clin., clinoid; CN, cranial nerve; Dup., duplicate; Eth., ethmoidal; Front., frontal; Inf., inferior; Inferolat., inferolateral; Lat., lateral; M., muscle; Med., medial; N., nerve; Nasocil., nasociliary; Obl., oblique; Ophth., ophthalmic; Rec., rectus; Seg., segment; Sup., superior; Tent., tentorial; Tr., trunk.

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FIGURE 7.7. Ophthalmic and central retinal arteries. A, superior view of the right orbit. The levator, superior rectus, and superior oblique muscles have been reflected to expose the ophthalmic artery coursing above the optic nerve. The ophthalmic artery passes above the optic nerve and between the superior oblique and the medial rectus muscles, where it gives rise to the anterior and posterior ethmoidal arteries. The anterior and posterior ethmoidal arteries pass through the anterior and posterior ethmoidal canals with the anterior and posterior ethmoidal nerves to supply the dura in the region of the cribriform plate and send branches that descend to supply the upper part of the nasal cavity. B, a segment of the optic nerve and ophthalmic artery have been removed to expose the central retinal artery arising as one of the first branches of the ophthalmic artery and entering the lower surface of the optic nerve. C, central retinal artery, inferior view. An ophthalmic artery, which courses below the optic nerve, has been retracted posteriorly to show the tortuous course of the central retinal artery before penetrating the optic nerve. The central retinal artery, which is the first or one of the earliest and smallest branches of the ophthalmic artery, pierces the lower surface of the nerve and courses a short distance inside the dural sheath of the nerve before passing to the center of the nerve, where it courses to the retina. D, inferior view. The inferior rectus has been retracted to expose a tortuous central retinal artery. Inset: Anterior view of the right orbit after removal of the globe. The central retinal artery, after penetrating the optic nerve, passes forward in the center of the nerve. The central retinal artery is a terminal branch without anastomotic connections. The ciliary arteries, coursing around the nerve, are divided into long and short and anterior ciliary arteries. The long and short ciliary arteries pierce the sclera around the optic nerve and supply the choroidal coat and ciliary processes. The anterior ciliary arteries are derived from the muscular branches of the ophthalmic artery and run to the front of the globe with the tendons of the extraocular muscles, where they pierce the sclera and end in the greater arterial circle of the iris. The subarachnoid space extends forward between the nerve and sheath. A., artery; Ant., anterior; Cent., central; Cil., ciliary; CN, cranial nerve; Eth., ethmoidal; Front., frontal; Inf., inferior; Lat., lateral; M., muscle; Med., medial; N., nerve; Nasocil., nasociliary; Obl., oblique; Ophth., ophthalmic; Post., posterior; Rec., rectus; Ret., retinal; Subarach., subarachnoid; Sup., superior.

FIGURE 7.8. Middle meningeal origin of the ophthalmic artery. A, posterior view of the right superior orbital fissure and the sphenoid ridge. The lacrimal foramen, through which the recurrent branch of the ophthalmic or lacrimal artery enters the orbit, is situated lateral to the superior orbital fissure. The recurrent branch frequently passes through the lateral margin of the superior orbital fissure, courses laterally below the sphenoid ridge, and turns forward through the meningolacrimal foramen to supply the periorbita in the roof of the orbit. Anastomosis from the frontal branch of the middle meningeal artery frequently contributes to the branch that passes through the lacrimal foramen. B, area just below the sphenoid ridge where there are often anastomoses between the recurrent branch of the lacrimal artery and the frontal branch of the middle meningeal artery. C, the right ophthalmic artery in the specimen with the anomalous left ophthalmic artery, shown in D F, has a normal origin from the internal carotid artery. It arises below the optic nerve, which has been reflected forward, and passes forward under the optic nerve to penetrate the dura lining the optic canal, reaching the orbital apex on the lateral side of the optic nerve. The annular tendon, from which the rectus muscles arise, has been opened and the lateral rectus muscle and the nerves passing through the superior orbital fissure have been folded downward with the lateral rectus muscle to expose the artery at the orbital apex. D, the dura covering the left cavernous sinus has been removed. The frontal branch of the left middle meningeal artery has been exposed up to where it passes through the superior orbital fissure. E, the levator and superior rectus muscles have been elevated to show the anomalous ophthalmic artery coursing in the orbit. F, enlarged view of the junction of the frontal branch of the middle meningeal artery with the ophthalmic artery. The wall of the middle meningeal artery embedded in the dura is thinner than after entering the orbit where it courses in the intraorbital fat. A., artery; Ant., anterior; Br., branch; Brs., branches; Car., carotid; Clin., clinoid; CN, cranial nerve; Div., division; Fiss., fissure; For., foramen; Front., frontal; Gr., greater; Lac., lacrimal; Less., lesser; M., muscle; Men., meningeal; Mid., middle; Nasocil., nasociliary; Ophth., ophthalmic; Orb., orbital; P.C.A., posterior cerebral artery; Rec., recurrent; Sphen., sphenoid; Sup., superior.

Venous Relationships

The venous spaces of the cavernous sinus fill the posterior margin of the superior orbital fissure and may extend forward along the medial and lower edges of the fissure (Figs. 7.2 and 7.3). The veins passing through the fissure empty into the cavernous sinus. The dural sinuses into which the sylvian veins empty commonly pass below the sphenoid ridge and along the intracranial edge of the lateral margin of the superior orbital fissure to reach the cavernous sinus. These sinuses are encountered in exposures directed through the lateral margin of the fissure.

The superior ophthalmic vein arises from tributaries in the superomedial part of the orbit, and the inferior ophthalmic vein arises from tributaries in the inferolateral part of the orbit (Figs. 7.2, 7.3, and 7.5). These veins are connected along the anterior margin of the orbit by large anastomotic channels formed by the facial and angular veins. This inferior ophthalmic vein may empty directly into the cavernous sinus, but more commonly, joins the superior ophthalmic vein to form a common stem that drains into the cavernous sinus.

The superior ophthalmic vein arises in the upper medial part of the orbit, passes backward on the lateral side of the superior oblique muscle, and crosses above the optic nerve to reach the lateral part of the orbit. It exits the muscle cone by passing between the heads of the superior and lateral rectus muscles and outside the annular tendon, through the narrow lateral part of the superior orbital fissure. It passes downward along the lateral margin of the annular tendon at the level of the superior orbital fissure, where it is commonly joined by the inferior ophthalmic vein to form a common trunk that enters the anteroinferior part of the cavernous sinus. Both the superior ophthalmic vein and the ophthalmic artery course along the superolateral aspect of the optic nerve in the orbital apex, but the vein passes outside the annular tendon and through the narrow lateral part of the superior orbital fissure, whereas the artery passes through the annular tendon and the optic foramen. The superior ophthalmic vein is anchored in the lateral corner of the superior orbital fissure by several fibrous bands that form a hammock around the vein, creating an obstacle to approaches to the lateral part of the orbital apex.

The inferior ophthalmic vein originates from tributaries on the anterior part of the floor and lateral wall of the orbit. It drains the inferior rectus and inferior oblique muscles, the lacrimal sac, and eyelids. It courses medially and posteriorly between the lateral and inferior rectus muscles with the branch of the oculomotor nerve to the inferior oblique muscle. It communicates with the pterygoid venous plexus through the inferior orbital fissure. It exits the muscle cone by passing between the origin of the lateral and inferior rectus muscles and the orbit, coursing below the annular tendon and through the inferior sector of the superior orbital fissure. It commonly joins the superior ophthalmic vein on the lateral aspect the annular tendon as it passes through the superior orbital fissure. The common trunk passes backward to enter the anteroinferior part of the cavernous sinus.

Muscular And Tendinous Relationships

The orbicularis oculi muscle surrounds the circumference of the orbit and spreads out on the temple and cheek (Fig. 7.9). It has orbital, palpebral, and lacrimal parts. The orbital part spreads in a wide band around the margin of the orbit. The palpebral part is located in the margins of the eyelids. The orbital part arises from the nasal process of the frontal bone, the frontal process of the maxilla, and the medial palpebral ligament. On the lateral side, it blends with the occipitofrontalis and the corrugator muscles. Many of the upper orbital fibers are inserted into the skin and subcutaneous tissues of the eyebrow. The palpebral part arises from the medial palpebral ligament and the bone above and below the ligament. Some of its fibers lie close to the margin of the eyelid behind the eyelashes. The lacrimal part extends behind the lacrimal sac and attaches to the lacrimal bone. The orbital part is the sphincter muscle of the eyelids. The palpebral portion closes the eyelids. The actions of the lacrimal part are important in tear transport.

The tarsi are two thin plates of dense fibrous tissue situated deep to the palpebral part of the orbicularis oculi muscle. The tarsi are placed in and give support and shape to each eyelid. Some of the fibers of the levator muscle are attached to the upper tarsus. The medial ends of the tarsi are attached by a tendinous band, the medial palpebral ligament, to the upper part of the lacrimal crest and the adjoining part of the frontal process of the maxilla in front of the lacrimal crest. The lateral ends of the tarsi are attached by a band, the lateral palpebral ligament, to a tubercle on the zygomatic bone immediately within the orbital margin. The orbital septum is a membranous sheet attached to the orbital margin where it is continuous with the periosteum along the anterior edge of the orbit. It separates the facial from the orbital structures. In the upper eyelid, the septum blends with the superficial part of the aponeurosis of the superior levator, and in the lower eyelid, it blends with the anterior surface of the tarsus. The medial and lateral cheek ligaments are fibrous expansions extending from sheaths of the lateral and medial rectus muscles that attach to the zygomatic and lacrimal bone, respectively. The cheek ligaments limit the actions of the lateral and medial rectus muscles.

The four rectus muscles arise from the annular tendon and form a cone around the neural and vascular structures passing through the annulus. The annular tendon is adherent to the dural sheath of the optic nerve and the periosteum above, below, and medial to the optic canal and to the lateral margin of the superior orbital fissure. The superior rectus muscle arises from the annular tendon, passes forward, and attaches to the sclera posterior to the margin of the cornea. The line of attachment is slightly oblique and curved. The superior oblique muscle arises from the periorbita covering the body of the sphenoid bone superomedial to the optic canal and runs forward, ending in a tendon that loops through the trochlea, a round tendon that attaches to the trochlear fossa of the frontal bone. After looping through the trochlea, the tendon passes laterally and posteriorly below the superior rectus muscle to insert on the sclera between the superior and lateral rectus muscles. The lateral rectus muscle arises from the annular tendon and adjacent part of the greater wing of the sphenoid bone and has a vertical line of attachment to the sclera posterior to the margin of the cornea. The inferior rectus muscle arises from the annular tendon and has an oblique line of attachment, with the medial side slightly anterior to the lateral side of the attachment. The inferior oblique muscle arises from the part of the orbital floor formed by the orbital surface of the maxilla in the area just lateral to the nasolacrimal duct, not from the orbital apex. It runs laterally and posteriorly, passing between the inferior rectus muscle and the orbital floor, and then between the lateral rectus muscle and the globe, to insert into the sclera between the superior and lateral rectus muscles near the insertion of the superior oblique muscle. The medial rectus muscle arises from the annular tendon, runs forward, and has a vertical line of attachment to the sclera. The orbital smooth muscle (Müller’s muscle) spans the upper margin of the inferior orbital fissure, and blends into the periorbita, the periosteum of the maxillary bone, and the perineurium of the infraorbital nerve.

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FIGURE 7.9. Anterior view of orbit and extraocular muscles. A, the skin around the right orbit has been removed to expose the orbicularis oculi muscle. This muscle surrounds the circumference of the orbit and spreads out on the temple and cheek. It has orbital, palpebral, and lacrimal parts. The orbital part of the orbicularis oculi spreads in a wide band around the margin of the orbit. The palpebral part is located in the margins of the eyelids. The orbital part arises from the nasal process of the frontal bone, the frontal process of the maxilla, and the medial palpebral ligament. On the lateral side, it blends with the occipitofrontalis and the corrugator muscles. Many of the upper orbital fibers are inserted into the skin and subcutaneous tissues of the eyebrow. The palpebral part arises from the medial palpebral ligament and the bone above and below the ligament. Some of its fibers lie close to the margin of the eyelid behind the eyelashes. The lacrimal part extends behind the lacrimal sac and attaches to the lacrimal bone. The orbicularis oculi is the sphincter muscle of the eyelids. The palpebral portion closes the eyelids. The actions of the lacrimal part are important in tear transport. B, the orbicular muscle has been removed to expose the upper and lower tarsi, thin plates of dense fibrous tissue situated deep to the palpebral part of the orbicularis oculi muscle. The tarsi are placed in and give support and shape to each eyelid. Some of the fibers of the levator muscle are attached to the upper tarsus. The medial ends of the tarsi are attached by a tendinous band, the medial canthal ligament, to the upper part of the lacrimal crest and the adjoining part of the frontal process of the maxilla in front of the lacrimal crest. The lateral ends of the tarsi are attached by a band, the lateral canthal ligament, to a tubercle on the zygomatic bone immediately within the orbital margin. The orbital septum that separates the facial from the orbital structures has been removed. It attaches to the orbital margin where it is continuous with the periosteum along the anterior edge of the orbit. In the upper eyelid it blends with the superficial part of the aponeurosis of the superior levator, and in the lower eyelid, it blends with the anterior surface of the tarsus. C, the globe and the optic nerve are surrounded by the four rectus, the levator, and two oblique muscles. The four rectus muscles arise from the annular tendon that surrounds the optic canal and adjunct part of the superior orbital fissure. The levator muscle arises from the lesser wing of the sphenoid above and anterior to the optic canal and fans out to have a broad attachment to the superior tarsus and the skin of the upper lid. The superior oblique muscle arises from the body of the sphenoid superomedial to the optic canal. The inferior oblique muscle arises from the orbital surface of the maxilla lateral to the nasolacrimal groove. The medial and lateral cheek ligaments (not shown) are fibrous expansions extending from sheaths of the lateral and medial rectus muscles that attach to the zygomatic and lacrimal bone, respectively, and limit the actions of the lateral and medial rectus muscles. D, globe depressed to show the insertion of the superior rectus muscle and the trochlea and distal tendon of the superior oblique muscle. The superior rectus muscle arises from the annular tendon, passes forward, and attaches to the sclera posterior to the margin of the cornea. The superior oblique muscle arises from the periorbita covering the body of the sphenoid bone superomedial to the optic canal and runs forward, ending in a tendon that loops through the trochlea, a round tendon that attaches to the trochlear fossa of the frontal bone. After looping through the trochlea, the tendon passes laterally and posteriorly below the superior rectus muscle to insert on the sclera between the superior and lateral rectus muscles. E, globe adducted to show the insertion of the lateral rectus muscle. The lateral rectus muscle arises from the annular tendon and adjacent part of the greater wing of the sphenoid bone and has a vertical line of attachment to the sclera. F, globe positioned to show the relationship of the inferior rectus and inferior oblique muscles. The inferior rectus muscle arises from the annular tendon and has an oblique line of attachment, with the medial side slightly anterior to the lateral side of the attachment. The inferior oblique muscle arises from the part of the orbital floor formed by the orbital surface of the maxilla in the area just lateral to the nasolacrimal duct, not from the orbital apex, and runs laterally and posteriorly, passing between the inferior rectus muscle and the orbital floor, and then between the lateral rectus muscle and the globe, to insert into the sclera between the superior and lateral rectus muscles near the insertion of the superior oblique muscle. Canth., canthal; Inf., inferior; Lat., lateral; Lev., levator; Lig., ligament; M., muscle; Med., medial; Obl., oblique; Orb., orbit; Rec., rectus; Sup., superior.

Surgical Considerations

The earliest reports of surgery for orbital lesions involved approaches directed through the lateral wall of the orbit (14, 18). The first report of a transcranial approach to the orbit was published in 1922 by Dandy (2). Since then, both extra- and intracranial routes to orbital lesions have been developed (1, 9, 12). The transcranial approach is commonly selected for tumors located in the orbital apex and/or optic canal, or involving both the orbit and adjacent intracranial areas (2, 6, 10). Tumors confined within the periorbita in the anterior two-thirds of the orbit can often be approached extracranially, but those located in the apical area, and especially those on the medial side of the optic nerve, often require a transcranial approach. An approach directed through the lateral orbital wall, involving an osteotomy of lateral rim and wall, is commonly selected for tumors confined to the superior, lateral, or inferior compartment of the orbit and those in the lateral part of the apex (14, 18). An approach directed along the medial orbital wall may be used for tumors located medial to the optic nerve that are not located deep in the apex (13, 18, 23).

The transcranial surgical approaches to the orbit may be arbitrarily divided into two types based on whether the orbital rim is or is not elevated in exposing the orbital lesion. Early approaches involved removal of a frontal or frontotemporal bone flap, with preservation of the supraorbital rim, and opening of the orbit behind the rim (3, 4, 9, 11, 16, 17, 19, 20). The transcranial approach can be tailored to the site of the lesion. For limited lesions, an approach directed through a small frontal craniotomy or frontotemporal craniotomy, with removal of the orbital roof and/or lateral wall, will provide access. However, for larger lesions, it is advantageous to elevate the orbital rim with the bone flap as is performed in the orbitofrontal or orbitozygomatic approach. In the orbitofrontal approach, only the upper rim of the orbit is elevated, and in the orbitozygomatic approach, the superior and lateral parts of the orbital rim are elevated. The orbitofrontal craniotomy would be selected for lesions involving the optic canal and orbital apex. The orbitozygomatic craniotomy would be selected for orbital lesions involving the middle fossa or superior orbital fissure, in addition to the orbit. In the one-piece orbitozygomatic approach, the orbital rim and frontotemporal bone flap are elevated together as a single bone flap. In the two-piece approach, the frontotemporal bone flap is elevated as the first piece and the osteotomy of the orbital rim and zygoma are elevated as the second piece. The orbitozygomatic approaches are reviewed in detail in Chapter 9.

Orbitofrontal Craniotomy

A bicoronal scalp flap is reflected to expose the site of the craniotomy, which includes the upper rim of the orbit (Fig. 7.10) (21, 22). The pericranium is reflected forward to expose the frontal bone and supraorbital margin. The supraorbital and supratrochlear nerves are exposed as they pass through a notch or foramina in the supraorbital rim. The supraorbital nerve may be released by removing bone with a drill or chisel from the lower margin of their foramen. The anterior edge of the temporalis muscle is reflected backward to expose the keyhole, the site of a burr hole that straddles the orbit and anterior cranial fossa, and which, at its depth, will expose periorbita on its lower edge and frontal dura on its upper edge. A zygomatic-temporal branch of the zygomatic nerve may be exposed on the zygomatic process of the frontal bone. The orbitofrontal bone flap includes the superior rim of the orbit and part of the orbital roof. The medial edge of the bone cut commonly extends through the frontal sinus. The thin part of the roof of the orbit behind the orbital rim is opened to prevent the fracture across the orbital roof, which occurs as the bone flap is elevated, from extending medially into the cribriform plate or ethmoid air cells.

The orbitofrontal craniotomy can be performed either as a one-piece exposure, in which the superior rim is elevated with the bone flap, or as a two-piece exposure, in which the small frontal bone flap above the supraorbital rim is elevated as the first piece and the superior rim is removed as the second piece. Approaching it in a two-piece manner allows more of the orbital roof to be preserved, because the bone cuts through the rim and roof can be performed under direct vision after the dura has been elevated from the orbital roof. In the one-piece exposure, the bone cuts through the orbital roof are made by depressing the periorbita and making the cut in the roof through the narrow space between the bone and periorbita. In addition, in the one-piece approach, it is not uncommon to have to fracture the last segment of the orbital roof between the medial and the lateral margins of the cuts in the roof, with the risk that the roof fracture can extend into the ethmoid air cells. This can be avoided if a burr hole is placed at the keyhole and the lateral part of the roof is opened through the keyhole. Another burr hole is then placed just above the medial part of the superior rim and opens through the anterior and posterior walls of the frontal sinus at the medial edge of the flap. The medial burr hole allows the medial part of the orbital rim and adjacent part of the orbital roof to be divided so that the bone flap can be elevated without having to fracture through the medial part of the roof. However, the two-piece approach obviates this, because the bone cuts in the orbital roof can be made extradurally under direct vision after elevating the dura from the roof.

Elevation of the bone flap exposes the periorbita of the orbital roof and the dura covering the anterior pole of the frontal lobe. Some lesions confined entirely to the orbit can be removed without opening the dura, but an intradural exposure is required for those lesions involving the optic canal, superior orbital fissure, or those involving the intradural surface of the orbital walls. The remaining roof of the orbit and optic canal are removed as needed. The dura can be opened and the frontal lobe elevated to expose the optic canal and optic nerve as needed. The olfactory tract is exposed above the cribriform plate. One olfactory nerve may have to be sacrificed. The falciform ligament, a dural fold that extends from the anterior clinoid process across the top of the optic nerve just proximal to the optic canal to the tuberculum sellae, may be opened (Figs. 7.2 and 7.10). At the site of this dural fold, the nerve is covered only by dura, rather than by dura and bone, as it is within the optic canal. The optic canal is opened to expose the intracanicular segment of the optic nerve. Opening the periorbita exposes the trochlear nerve and the supraorbital and supratrochlear branches of the frontal nerve, all of which course immediately beneath and can often be seen through the periorbita. The trochlear nerve passes medially above the levator muscle to reach the superior oblique muscle. Three routes through an orbitofrontal craniotomy can be taken to the orbital contents: medial, lateral, and central. These approaches can also be used with an orbitozygomatic craniotomy.

The Medial Orbitofrontal Approach

The medial approach is directed through the space between the superior oblique muscle, which is retracted medially, and the levator and superior rectus muscles, both of which are retracted laterally (Fig. 7.10, E and F). This approach exposes the optic nerve throughout the interval from the globe to the optic canal. It is the most direct surgical approach to the apical part of the optic nerve.

Four structures are located on the lateral side of the optic nerve near the orbital apex that pass above the optic nerve to reach the medial part of the orbit. These structures, the trochlear nerve, ophthalmic artery, nasociliary nerve, and superior ophthalmic vein, cross above the nerve an average of 3.2 mm, 10.6 mm, 10.0 mm, and 23.9 mm distal to the anterior opening of the optic canal, respectively (21). In approximately 15% of orbits, the ophthalmic artery will pass below rather than above the optic nerve. The incision for opening the annular tendon, if needed, is directed between the attachment of the superior and medial rectus muscles. Before the annulus is opened, the trochlear nerve is separated from the adjacent tissues above the orbital apex to prevent its damage in opening the optic sheath. Opening the annular tendon and optic sheath exposes the medial and superior surface of the optic nerve from the globe to the optic chiasm. This incision provides excellent exposure of the optic nerve and the ophthalmic artery in the optic canal and orbital apex, but yields limited access to the structures passing through the superior orbital fissure on the lateral side of the optic nerve.

The following structures are on the medial side of the optic nerve: anteriorly near the globe, the ophthalmic artery, the nasociliary nerve, and the superior ophthalmic vein; and posteriorly near the orbital apex, the trochlear nerve and the posterior ethmoidal artery. The interval between the anteriorly and posteriorly situated structures is free of important structures, thus providing a route to the optic nerve. However, the space between the superior oblique and the levator muscles is much narrower than the space between the levator and the lateral rectus muscles used for the lateral approach. The angle through which the approach can be made is also limited in width by the medial margin of the frontal craniotomy.

The medial approach is selected for lesions located superomedial to the optic nerve or for cases in which there is a need to expose the optic nerve from the optic canal to the globe. It is the approach most commonly selected for tumors of the optic sheath or optic nerve. The medial approach is not suitable for lesions located on the lateral side of the optic nerve or for those involving the superior orbital fissure and the cavernous sinus.

The Central Orbitofrontal Approach

In the central approach, the levator muscle is retracted medially and the superior rectus muscle is retracted laterally (Fig. 7.10, J and K). The central approach, which is the least used of the three approaches directed through an orbitofrontal craniotomy, is the most direct and shortest way to the midportion of the intraorbital segment of the optic nerve. There are two variants of this approach; the choice depends on whether the frontal nerve is retracted medially with the levator muscle or laterally with the superior rectus muscle. The second variant, in which the frontal nerve is retracted laterally with the superior rectus muscle, provides a wider exposure of the orbital apex than the exposure in which the frontal nerve is retracted medially with the levator muscle.

The approach in which the frontal nerve is retracted medially with the levator muscle carries less risk of damaging the frontal nerve, because the frontal nerve and the levator muscle, on which the frontal nerve courses, do not have to be separated as they do when the frontal nerve is retracted laterally with the superior rectus muscle. On the other hand, maintaining the frontal nerve on the levator muscle blocks the approach to the deep apical region lateral to the optic nerve and yields access to only the midportion of the intraorbital segment of the optic nerve. Even when the frontal nerve is retracted laterally with the superior rectus muscle, the view into the orbital apex may be limited by the overlap of the origin of the levator and superior rectus muscles, which are located one above the other. Another disadvantage of this approach is that the orbital septum that covers the lower side of the superior rectus muscle must be opened, thus risking damage to the ophthalmic artery and the nasociliary nerve, which cross the optic nerve just beneath the septum. Structures seen in the exposure between the retracted muscles include the superior ophthalmic vein, ciliary arteries and nerves, nasociliary nerve, branch of the oculomotor nerve to the levator muscle, and the ophthalmic artery and its branches to the levator and superior rectus muscles. The many structures in the exposure create a complicated field, requiring considerable care to avoid injuring the exposed structures. However, this route is the shortest, most direct one to the middle third of the optic nerve in its intraorbital portion.

The central approach may be selected for biopsy or removal of lesions located in the midportion of the intraorbital segment of the optic nerve. The variant in which the frontal nerve is retracted laterally provides access to the posterior third of the intraorbital portion of the optic nerve.

The Lateral Orbitofrontal Approach

For the lateral approach, the optic nerve is approached between the lateral rectus muscle, which is retracted laterally, and the superior rectus and levator muscles, both of which are retracted medially (Fig. 7.10, G–I). The lateral approach provides a wider working space than the medial or central approach. The wider angle of access allows the approach to be directed through all parts of the orbitofrontal exposure. It is the best of the three orbitofrontal routes for exposing the deep apical area on the lateral side of the optic nerve. It is possible to expose the superior orbital fissure and adjacent part of the cavernous sinus in combination with the lateral approach if it is combined with an orbitozygomatic craniotomy, in which the superior and lateral part of the orbital rim and the roof and lateral wall of the orbit are elevated with a frontotemporal bone flap. This orbitozygomatic craniotomy in combination with the lateral approach is suitable for lesions that involve the area along the anterior clinoid process and sphenoid ridge and middle fossa and extend through the superior orbital fissure into the orbit on the lateral side of the optic nerve.

There are two variants of the lateral approach; the choice is determined by whether the superior ophthalmic vein is retracted medially or laterally. If the superior ophthalmic vein is retracted medially with the superior rectus and levator muscles, it is not necessary to dissect the vein from the connective tissue, which forms a hammock around the vein adjacent to the superior fissure. It is easy to expose the optic nerve lateral to the fibrous hammock without risk of damage to the intraorbital connective tissue, which contains the ciliary nerves. However, access to the deep apical area is limited because the superior ophthalmic vein blocks the line of view. The superior ophthalmic vein enters the superior orbital fissure an average of 9.7 mm lateral to the anterior edge of the optic strut (21). It commonly passes through the superior edge of the fissure, but it may also pass through the fissure below the superior margin, in which case it is difficult to approach the deep apical area because the vein blocks access to the area on the medial side of the superior orbital fissure.

The variant in which the superior ophthalmic vein and connective tissue hammock are dissected free of adjacent structures and retracted laterally with the lateral rectus muscle provides access to lesions in the lateral part of the deep apical area that may also involve the superior orbital fissure and cavernous sinus. To retract the superior ophthalmic vein laterally, the orbital septum (which runs under the surface of the superior rectus muscle and connects to the superior ophthalmic vein) must be opened, thus risking damage to the cranial nerves that pass through the superior orbital fissure and to the ciliary ganglion, which are normally protected beneath the orbital septum. In the approach in which the vein is retracted laterally, the annular tendon is easily visualized between the origins of the superior and lateral rectus muscles. Dividing the annular tendon between the superior and lateral rectus muscles exposes the deep apical area at its junction with the superior orbital fissure.

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FIGURE 7.10. A-E. Orbitofrontal craniotomy in which the supraorbital rim and the anterior part of the orbital roof are elevated with the frontal bone flap. A, a bicoronal scalp flap has been reflected forward to expose the frontal bone and supraorbital margin. The supraorbital nerve has been released by removing bone from the lower margin of the supraorbital foramen. The craniotome has cut around the margin of the orbitofrontal bone flap, which includes the supraorbital ridge and part of the orbital roof. The temporalis muscle has been reflected backward to expose the keyhole, the site of a burr hole, which at its depth will expose periorbita in its lower edge and frontal dura in its upper edge. A zygomatic-temporal branch of the zygomatic nerve is exposed on the zygomatic process of the frontal bone. B, removal of the bone flap exposes the periorbita of the orbital roof and the dura covering the frontal lobe. The medial edge of the bone cut should extend completely through the orbital rim and partially divide the thin part of the roof of the orbit behind the orbital rim to prevent the fracture across the orbital roof, which occurs as the bone flap is elevated, from extending medially into the cribriform plate or ethmoid air cells. C, the roof of the orbit has been removed, the frontal lobe elevated, and the dura and arachnoid opened to expose the optic nerve intracranially and in the optic canal. The optic canal has been unroofed to expose the intracanicular segment of the optic nerve. The falciform ligament is a dural fold, which extends from the anterior clinoid across the top of the optic nerve just proximal to the optic canal to the tuberculum sellae. At the site of this dural fold, the nerve is covered only by dura, rather than by dura and bone, as it is within the optic canal. The anterior clinoid artery, situated on the lateral side of the optic nerve, has been removed. The anterior cerebral artery courses above the optic chiasm. D, the periorbita has been opened and the orbital fat removed to expose the trochlear nerve, the supraorbital and supratrochlear branches of the frontal nerve, and the levator and superior oblique muscles. The trochlear nerve passes medially above the levator muscle to reach the superior oblique muscle. The superior ophthalmic vein passes through the lateral part of the superior orbital fissure. E and F, medial route to the optic nerve. E, the medial approach is directed through the interval between the superior oblique and the levator muscles. In the medial route there are no neural and vascular structures between the ophthalmic artery and orbital apex, except the trochlear nerve, which crosses above the levator muscle in the extraconal area. The ophthalmic artery, superior ophthalmic vein, and nasociliary nerve are situated on the lateral side of the optic nerve at the orbital apex, but further forward they cross above the nerve to reach the medial part of the orbit.

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FIGURE 7.10. F-K. Orbitofrontal craniotomy in which the supraorbital rim and the anterior part of the orbital roof are elevated with the frontal bone flap. F, an incision has been extended backward through the annular tendon between the superior and medial rectus muscles and through the optic sheath to expose the full length of the optic nerve. The trochlear nerve passes above the levator muscle at the orbital apex in its passage to the superior oblique muscle and should be protected in completing the incision through the annular tendon and along the optic sheath. This type of incision in the annular tendon can be combined with the medial supraorbital approach to provide access to the optic nerve from the optic chiasm to the globe. The sphenoid and ethmoidal sinuses are exposed on the medial side of the orbit. G and H, lateral route to the intraconal and apical area. The lateral route to the optic nerve is directed through the interval between the levator and superior rectus muscle medially and the lateral rectus muscle laterally. This route is often selected for lesions that involve the area lateral to the optic nerve or those extending through the superior orbital fissure. G, the levator and superior rectus muscles and the superior ophthalmic vein have been retracted medially to expose the intraorbital part of the optic nerve. The superior ophthalmic vein blocks the view of the deep apical area. H, the superior ophthalmic vein has been displaced laterally to expose the deep apical area. It blocks the view of the apical area, as shown in G, when it is retracted medially. I, the annular tendon has been divided between the origin of the lateral and superior rectus muscles, as can be performed in the lateral approach. The origin of the superior rectus muscle from the annular tendon has been retracted medially and the origin of the lateral rectus muscle has been retracted laterally. This incision can be combined with a lateral supraorbital approach to increase access to the structures in the superior orbital fissure. The nasociliary nerve crosses above the optic nerve in front of the annular tendon and orbital apex. The superior division of the oculomotor nerve sends branches into the lower surface of the superior rectus and levator muscle. The abducens nerve passes through the superior orbital fissure below the nasociliary nerve and enters the medial surface of the lateral rectus muscle. The ophthalmic artery courses on the lateral side of the optic nerve at the orbital apex. The sensory root to the ciliary ganglion arises from the nasociliary nerve and the motor parasympathetic root arises from the branch of the inferior division to the inferior oblique muscle. J and K, central route to the optic nerve. This route is directed between the levator and superior rectus muscles. J, the levator and the frontal nerve are retracted medially, and the superior rectus muscle is retracted laterally. This exposes the middle third of the intraorbital portion of the optic nerve. It is the shortest route through the orbital roof to the optic nerve. The ophthalmic artery and the nasociliary nerve cross above the optic nerve. The branch of the superior division of the oculomotor nerve, which enters the lower surface of the superior rectus and levator muscles, crosses the field. K, a second variant of the central approach, in which the frontal nerve is retracted laterally with the superior rectus muscle. This approach provides a wider exposure of the optic nerve in the orbital apex than the exposure in which the branches of the frontal nerve are retracted medially with the levator muscle as shown in J. The site at which the medial and superior rectus muscles arise from the annular tendon is also exposed. A., artery; A.C.A., anterior cerebral artery; Ant., anterior; Car., carotid; Cil., ciliary; Clin., clinoid; CN, cranial nerve; Div., division; Eth., ethmoid, ethmoidal; Falc., falciform; Front., frontal; Gang., ganglion; Inf., inferior; Lac., lacrimal; Lat., lateral; Lev., levator; Lig., ligament; M., muscle; N., nerve; Nasocil., nasociliary; Obl., oblique; Ophth., ophthalmic; Rec., rectus; Sup., superior; Supraorb., supraorbital; Supratroch., supratrochlear; Temp., temporal; V., vein; Zygotemp., zygotemporal.

Lateral Wall Approach (Sphenozygomatic Approach)

An approach directed through the lateral orbital wall, involving an osteotomy of the lateral orbital rim and wall, is selected for tumors confined to the superior, temporal, or inferior compartment of the orbit and those in the lateral part of the apex (14, 18) (Fig. 7.11). The curved skin incision begins in front of the ear, extends forward along the upper edge of the zygoma, and turns upward along the lateral rim of the orbit to expose the superficial temporal artery and the vein and zygomaticotemporal nerve. Opening the skin and subcutaneous tissues over the lateral wall of the orbit exposes the branches of the superficial temporal artery, the branches of the facial nerve to the orbicularis and frontalis muscles, the zygomaticotemporal branch of the maxillary nerve, and the auriculotemporal branch of the mandibular nerve, all of which course in the subcutaneous tissues superficial to the temporalis muscle. The branches of the facial nerve should be protected and preserved, and if divided in the exposure they should be reapproximated at the time of closure.

Elevating the lateral rim and wall exposes the periorbita anterior to the lateral edge of the superior orbital fissure. Opening the periorbita exposes the lateral rectus muscle, the lacrimal artery and nerve, and the lacrimal gland. Retracting the orbital fat exposes the structures lateral to and above and below the optic nerve, and the insertion of the lateral rectus and inferior oblique muscles on the globe. The lateral orbital rim and wall, which has been elevated in a single piece, is replaced after removing an orbital lesion.

The orbitozygomatic craniotomy, which is reviewed in Chapter 9, can be used if the lateral orbital exposure needs to be combined with the extradural exposure of the superior orbital fissure, orbital roof, anterior clinoid process, and cavernous sinus, and intradural exposure of the optic nerve, internal carotid artery and its branches, and the roof and lateral wall of the cavernous sinus. The orbitozygomatic approach can also be tailored to include only the lateral wall and not the orbital roof.

Exposing the superior orbital fissure and its sectors requires at least limited exposure of the cavernous sinus posteriorly and the orbit anteriorly. This is usually achieved with an orbitozygomatic craniotomy. Fortunately, all of the nerves of the cavernous sinus, except the abducens nerve, can be exposed by peeling away the outer layer of dura in the lateral sinus wall, while leaving the inner layer investing the nerves intact. It is possible to expose the full course of the oculomotor and trochlear nerves from their entrance into the roof of the sinus and the ophthalmic nerve from its origin through the fissure and into the orbit without opening into the major venous spaces of the sinus, because these nerves course in the inner dural layer of the lateral sinus wall. Exposure of the abducens nerve is more hazardous, because it courses within the sinus and is adherent to the lateral surface of the intracavernous carotid artery. Removing the bony margins of the superior orbital fissure without exposing the neural structures will often suffice in dealing with tumors, such as sphenoid ridge or clinoidal meningiomas, that have grown through the greater and lesser sphenoid wings to compress but not infiltrate the structures coursing through the fissure. In other cases, tumors such as schwannomas and meningiomas may grow along the nerves, requiring that the various sectors of the fissure be opened. Removal of the bone in the margin of the superior orbital fissure and anterior clinoid process are frequent steps in exposing tumors and aneurysms in the region. Care is required in removing the anterior clinoid process to avoid damaging the optic and oculomotor nerves. Both the anterior clinoid process and the optic strut may contain air cells that communicate with the sphenoid sinus and must be closed, if opened, to prevent cerebrospinal fluid rhinorrhea.

The periosteal margins of the superior orbital fissure may be opened at several sites with or without opening the annular tendon (21, 22). The fissure’s central sector and the oculomotor foramen can be opened with an incision directed through the annular tendon between the origin of the superior and lateral rectus muscles (Fig. 7.3 and 7.10, F and I). It is important to remember that the superior ophthalmic vein exits the extraocular muscle cone by passing between the origin of the superior and lateral rectus muscles (Fig. 7.5). The trochlear, frontal, and lacrimal nerves course lateral to this opening through the annular tendon. Openings into the lateral sector are best directed through the upper margin of the fissure, because the superior ophthalmic vein courses along the lower margin of the lateral sector. The large sylvian veins that empty into the cavernous sinus also pass downward along the lower edge of the lateral sector. Care is required to avoid injury to the trochlear nerve when opening the upper margin of the lateral sector because this nerve hugs the upper margin of this sector. The opening in the lateral sector should be directed through the area medial to the superior ophthalmic vein. Another incision that may be used to open the central sector is directed through the lateral margin of the fissure and annular tendon between the origins of the lateral and inferior rectus muscles. This incision is more difficult to complete than the opening between the origin of the lateral and superior rectus muscles because of the attachment of the annular tendon and a portion of the lateral rectus muscle to the prominence on the lateral margin of the fissure. The inferior ophthalmic vein is commonly encountered in this opening, because it exits the muscle cone by coursing between the origin of the lateral and inferior rectus muscles.

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FIGURE 7.11. A-D. Lateral orbital approach. A, structures superficial to the lateral orbital wall include the branches of the facial nerve to the orbicularis oculi and frontalis muscles, which cross the midportion of the zygomatic arch; the anterior branch of the superficial temporal artery; and the temporalis muscle, which passes medial to the zygomatic arch to insert on the coronoid process of the mandible. B–E, exposure obtained with a lateral orbitotomy. B, the curved skin incision begins in front of the ear, extends forward along the upper edge of the zygoma, and turns upward along the lateral rim of the orbit. The superficial temporal artery and vein are exposed. A zygomaticotemporal nerve branch of the maxillary nerve passes through the lateral orbital wall to convey sensation to the temple. Care is required to preserve the branches of the facial nerve to the orbicularis oculi and frontalis muscles and, if transected, reapproximation should be attempted at the end of the operation. C, the lateral orbital rim formed by the frontal process of the zygomatic bone and the zygomatic process of the frontal bone has been exposed. The temporalis muscle has been elevated from the lateral orbital wall. D, the part of the lateral wall of the orbit formed by the frontal and zygomatic bones and the adjacent part of the sphenoid wings has been elevated as a small bone flap to expose the periorbita of the anterior two-thirds of the orbital wall. The lacrimal artery and nerve course in the orbital fat above the lateral rectus muscle. The orbital part of the lacrimal gland is exposed outside the orbital fat. The lateral orbital rim, which has been removed in a single piece, is replaced after removing the orbital lesion.

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FIGURE 7.11. E-I. Lateral orbital approach. E, the orbital fat has been removed to expose the optic nerve and insertion of the lateral rectus and inferior oblique muscles on the globe. The superior ophthalmic vein, the nasociliary nerve, and the lacrimal and ciliary arteries and nerves are exposed above the lateral rectus muscle. F, combining the lateral orbital exposure with a frontotemporal craniotomy permits exposure of the superior orbital fissure, anterior cavernous sinus, and the frontal and temporal lobes adjoining the sylvian fissure. The lateral orbital wall has been removed to expose the periorbita. G, the combined craniotomy and lateral orbitotomy exposures include the anterior part of cavernous sinus, the superior orbital fissure, and the lateral orbit. The anterior clinoid process and a portion of the optic strut have been removed. The bone around the optic canal has been removed to expose the optic sheath. H, the periorbita has been opened to expose the lateral rectus muscle. The lacrimal and frontal nerves course through the lateral part of the superior orbital fissure. The superior ophthalmic vein courses along the lateral margin of the annular tendon. I, the lateral rectus muscle has been reflected posteriorly. The ciliary ganglion is located on the lateral side of the ophthalmic artery and optic nerves. The abducens nerve enters the medial side of the lateral rectus muscle. The motor root of the ciliary ganglion arises from the branch of the inferior oculomotor division to the inferior oblique muscle. The sensory root of the ciliary ganglion arises from the nasociliary. The ciliary ganglion gives rise to short ciliary nerves. A., artery; Car., carotid; Cil., ciliary; CN, cranial nerve; Fiss., fissure; Front., frontal; Frontozygo., frontozygomatic; Gang., ganglion; Inf., inferior; Lac., lacrimal; Lat., lateral; Lig., ligament; M., muscle; N., nerve; Nasocil., nasociliary; Obl., oblique; Ophth., ophthalmic; Orb., orbital; Rec., rectus; Sup., superior; Supf., superficial; Temp., temporal, temporalis; V., vein; Zygo., zygomatic; Zygomaticotemp., zygomaticotemporal.

Transmaxillary Approach

This transmaxillary approach, directed through the orbital floor, is most commonly performed using a sublabial incision in the gingivobuccal margin rather than through an incision on the face (7, 8). Soft tissues are elevated to expose the anterior surface of the right maxilla (Figs. 7.12 and 7.13). The approach can be completed without dividing the infraorbital nerve at the infraorbital foramen, but if divided, it can be resutured at the time of closing. Removing the anterior wall of the maxillary sinus exposes the infraorbital canal in the roof of the sinus, which forms the orbital floor. Opening the orbital floor exposes the periorbita covering the orbital floor and the infraorbital artery and nerve. Structures that may be exposed include the inferior and medial rectus and inferior oblique muscles, the inferior division of the oculomotor nerve and its branches, the ciliary ganglion and its roots, plus short ciliary nerves that arise in the ciliary ganglion and pierce the sclera around the optic nerve and the central retinal artery. This approach may be used to reconstruct the orbital floor after trauma or to open the floor for orbital decompression.

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FIGURE 7.12. Transmaxillary exposure of the orbit. A, this approach is usually performed through a degloving incision in the buccogingival junction rather than through an incision along the margin of the nose. The upper lip and cheek flap have been reflected laterally and the anterior wall of the maxilla has been opened to expose the maxillary sinus. B, enlarged view. The posterior wall of the maxillary sinus has been removed to expose the pterygopalatine fossa. The maxillary nerve enters the pterygopalatine fossa by passing through the foramen rotundum, where it gives rise to communicating rami to the pterygopalatine ganglion and infraorbital and palatine nerves. The terminal branches of the maxillary artery also course through the pterygopalatine fossa. C, inferior view of another orbit after the orbital floor has been removed and the infraorbital nerve reflected posteriorly to expose the periorbita and orbital fat. D, the orbital fat has been removed to expose the medial and inferior rectus and inferior oblique muscles. The inferior oblique muscle arises from the medial orbital wall and passes laterally below the inferior rectus muscle to insert on the sclera. The branch of the inferior division of the oculomotor nerve to the inferior oblique muscle courses along the lateral side of the inferior rectus muscle. E,  the inferior rectus muscle has been divided and reflected backward. The ophthalmic artery, in this case, courses below the optic nerve, as occurs in approximately 15% of orbits. The inferior division of the oculomotor nerve gives rise to individual branches to the medial rectus, inferior oblique, and inferior rectus muscles. A tortuous central retinal artery arises below and enters the lower margin of the optic nerve. F, the ophthalmic artery has been retracted medially to expose the origin of the parasympathetic motor root to the ciliary ganglion, which courses from the branch of the inferior oculomotor division to the inferior oblique. The ganglion gives rise to short ciliary nerves, which are distributed to the globe. A., artery; Cent., central; Cil., ciliary; CN, cranial nerve; Comm., communicating; Fiss., fissure; Gang., ganglion; Gr., greater; Inf., inferior; Infraorb., infraorbital; M., muscle; Max., maxillary; Med., medial; N., nerve; Obl., oblique; Orb., orbital; Palat., palatine; Pterygopal., pterygopalatine; Rec., rectus; Ret., retinal.

Medial Orbital and Transethmoidal Approaches

The medial orbital incision can be used to provide access to the area lateral to the lacrimal and ethmoid bones back to the orbital apex, and with removal with some of the ethmoid air cells and sphenoid sinus facing the orbit, the optic canal can be exposed or decompressed (Fig. 7.13) (7, 8). The medial orbital incision extends between the medial orbit and nose along the frontal process of the maxillary bone. The exposure is extended using subperiosteal and subperiorbital dissection except at the medial canthal ligament, which is attached to the anterior and posterior margins of the lacrimal groove, and which should be divided or elevated in such a way that it can be preserved and reapproximated if divided. The lacrimal sac, which sits in the lacrimal groove, can usually be elevated. Behind this, the anterior ethmoidal branch of the ophthalmic artery is encountered as it penetrates the periorbita to enter the anterior ethmoidal canal. This artery is divided if a more posterior exposure is needed. As the exposure proceeds, posteriorly along the orbital plate of the ethmoid, the posterior ethmoidal artery is encountered entering the posterior ethmoidal canal. It passes medially along the planum sphenoidale and can be divided. The optic canal is found approximately 7 mm behind the posterior ethmoidal canal (8). Removing some of the ethmoid plate and adjacent part of the sphenoid sinus will expose the optic nerve in the optic canal. Extending the medial orbital incision downward, lateral to the nose, will allow access to the anterior part of the maxilla. Removing the medial part of the anterior wall of the maxillary sinus bordering the nasal cavity provides access to the medial orbital floor.

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FIGURE 7.13. Medial orbital approach. A–C, medial orbital exposure. A, the medial orbital incision on the left side is shown in the inset. The approach exposes the medial orbital wall, ethmoid air cells, and sphenoid sinus back to the level of the optic canal. The periorbita has been elevated from the frontal process of the maxillary bone and adjacent frontal bone forming the medial part of the orbital rim to expose the medial canthal ligament, which, if divided, should be reapproximated at the end of the procedure to maintain canthal balance. B, the medial palpebral ligament has been divided and the edges of the divided ligament have been preserved for re-approximation at the end of the procedure. The lacrimal sac has been retracted laterally. The exposure extends backward along the lacrimal and ethmoid bones to the level where the anterior ethmoidal artery enters the anterior ethmoidal canal. The lacrimal groove, in which the lacrimal sac sits, is formed anteriorly by the maxilla and posteriorly by the lacrimal bone. C, the exposure has been extended backward along the ethmoid, lacrimal, and frontal bones, past the level where the anterior and posterior ethmoidal arteries enter the anterior and posterior ethmoidal canal to the orbital apex and anterior end of the optic canal. The medial ethmoid air cells and adjacent part of the sphenoid sinus can be removed to expose the optic nerve in the optic canal. This approach is sometimes used to decompress the optic canal. D–F, combined medial orbital and maxillary exposures. D, the exposure includes not only the medial orbital wall, but also the adjacent part of the floor. Two small maxillary osteotomies have been completed. The medial one includes the part of the maxilla forming the anterior wall of the nasal cavity. The lateral osteotomy exposes the anterior part of the maxillary sinus. The medial palpebral ligament has been divided to expose the medial wall of the orbit. E, removing the medial osteotomy fragment exposes the nasal cavity and the nasal septum and inferior and middle conchae. Removing the lateral osteotomy fragment exposes the maxillary sinus, medial part of the orbital floor, and the nasolacrimal duct, which courses along the medial maxillary wall and opens below the inferior concha into the inferior meatus. F, the nasolacrimal duct and lacrimal sac have been retracted laterally and the exposure extended along the medial orbital wall to the area posterior to where the anterior ethmoidal artery was divided. The posterior part of the osseous nasolacrimal canal has been exposed. A., artery; Ant., anterior; Canth., canthal; Eth., ethmoid, ethmoidal; Front., frontal; Inf., inferior; Lac., lacrimal; Lig., ligament; Max., maxillary; Med., medial; Mid., middle; N., nerve; Nasolac., nasolacrimal; Post., posterior; Proc., process.

Contributor: Albert L. Rhoton, Jr., MD

Content from Rhoton AL. The Orbit. Neurosurgery 51(1), 2002. 10.1097/00006123-200210001-00008. 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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