Olfactory Groove Meningioma
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Resection of Olfactory Groove Meningiomas is quite satisfying and often leads to improved outcomes. Let's review some of the tenants for resection of such tumors. This is a 31 year old female who presented with confusion and personality change. And on MRI evaluation was diagnosed with a classic olfactory groove meningoma with evidence of bifrontal edema. The location or neurovascular structures are specially important, more specifically the anterior cerebral arteries are often encased or displaced more posteriorly. This tumor does not seem to invade the optic canal, but does reach the anterior aspect of the optic apparatus. Furthermore it does not invade the sella turcica and it has a very broad base attachment as expected to the area of the olfactory groove and planum sphenoidale. This tumor was approached through a left front temporal craniotomy. I install a lumbar drain before patient positioning. The early drainage of CSF, allows decompression, avoids brain herniation, during dural opening and early stages of tumor devascularization. Aggressive CSF drainage should be avoided to avoid any transtentorial herniation due to mass effect of the tumor. Here's the extent of the craniotomy. The Bonny exposure extends to the mid-pupillary line ipsilaterally. Most of the exposures frontal with minimal exposure of the anterior temporal lobe. Obviously the Sylvian fissure is also exposed. I do not believe in organized psychosomatic craniotomy, add significantly to the ability to remove the tumor. During dura opening, approximately 30 to 40 CC of CSF is drained. The dura is incised and a curvilinear fashion. Careful epidural hemostasis is obtained. The edema associated with most of these tumors, often leads to significant brain herniation during dural opening, if lumbar drainage is not used. Upon opening of the dura, I will first attempt to find the neurovascular structures along the posterior pole of the tumor, including the optic nerve and the carotid artery. The pterional approach offers a number of advantages over the bifrontal corridor for resection of these tumors, more specifically, the opening is less disruptive, the neurovascular structures are identified at the posterior pole of the tumor early on through a lateral trajectory, and the frontal sinuses are not violated. In addition, the anterior aspect of the superior sagittal sinus is not manipulated through the pterional craniotomy. Upon mobilization of the dura, further a CSF drainage is conducted until adequate brain relaxation is achieved. Here is the next step which involves gentle elevation of the frontal lobe, identification of the optic nerve and carotid artery. So they are protected during the later stages of tumor devascularization. The bifrontal corridor places the tumor between the surgeon and the neurovascular structures, and can therefore add some uncertainty to the location of these important structures. Further CSF has drained upon opening of the optical carotid cisterns. Here's the optic nerve, Here's the carotid artery and here's the poster a pole of the tumor. By opening these ragnar bands, a surgical plane between the posterior pole of the tumor and the optic nerve can be created. In addition, if the tumor has invaded the optic canal, the nerve can be decompressed early on. Here's the optic nerve, carotid artery, the base of the tumor. My first maneuver will involve dissecting the anterior limb of the Sylvian fissure to allow the frontal lobe tumor be mobilized away from the anterior skull base. Here's the Sylvian fissure, only the sphenoidal segment of the fissure is necessary to be dissected. Most of the veins are protected as much as possible. I use a round arachnoid knife and try to avoid any injury to the opercular during the dissection. One or two of the small bridging veins may have to be sacrificed. Here's the tumor, readily available, through the lateral trajectory, you can see the olfactory nerve, very much in case and destroyed by the tumor. The key maneuver in this operation is aggressive devascularization of the base of the tumor, all the way to the contralateral anterior skull base. This is performed before the tumor is debarked. This early devascularization minimizes blood loss, and also provides it clear operative field for microsurgery and dissection of the anterior cerebral arteries during the later stages of the operation. The ethmoidal arteries often provide most of the vascularity to these tumors, and it can be quite challenging to obtain hemostasis at the very base of the tumor. I have periodical even use the bovie electrocautery to quiet coagulate the feeding vessels originating through the bone and the dura and feeding the tumor. The bifora forceps may not effectively control the bleeding, across the transosseous and transdural feeding vessels. Hang on the tumors like a mushroom, therefore the base of the tumor is smaller, than the top of the tumor. Here, you can see how early identification optic nerve protects the nerve during the devascularization of the posterior pastes of the tumor. Early brain relaxation allows aggressive tumor devascularization without significant brain retraction or transgression. This tumor appeared to be soft after it was devascularized, and following complete devascularization of the base of the tumor, it's been debarked. All the orbital frontal or frontal pole arteries draping over the superior pole of the tumor are obviously protected. The olfactory nerves are frequently not salvageable, but most patients that Harbor such large tumors are already anosmic. Here's more of the capsule of the tumor that is being further dissected from the pure surfaces of the subfrontal brain. This' contralateral olfactory nerve. The transcranial corridor is the only corridor that offers an opportunity to preserve olfaction in medium size tumors. Unfortunately the opportunity to preserve olfaction is not available for the endonasal corridor. Again, the tumor is being delivered into our resection cavity. Some of the strands related to the capsule of the tumor is also being dissected away. Here's the anterior falx and crista galli. I look around the falx and try to remove a tumor that's hiding on the contralateral aspect of the falx and crista galli. I frequently remove part of the Fox here in order to be able to look around it. You can see that portion of the Fox was transected and I'm reaching across to remove tumor. Kerosene ronguers are being used to remove part of the anterior falx and crista galli, so that the tumor on the right side of the falx is accessed. Any part of the falx that could be affected by the tumor is either resected or heavily coagulated. You can see part of the parenchyma of the subfrontal area and portion of tumors that had invaded the pia. I'm relatively satisfied with the extent of the section, the portion of the dura along the olfactory groove and planum sphenoidale is heavily coagulated to hopefully decrease the risk of future tumor recurrence. You can see the anterior cerebral arteries were not hurt here in this case and were protected during tumor mobilization. Base of the tumor was heavily coagulated. The arachnoid layers over the optic nerve and carotid artery were protected. Following hemostasis, closure is conducted in standard fashion. Fixed retractors are avoided. You can see the relatively healthy status of the frontal lobe. Closure is conducted again, in standard fashion. Post-operative MRI in this case demonstrated gross total removal of the mess. Thank you.
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