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Olfactory Groove Meningioma: Principles of Transcranial Resection

April 28, 2016


Let's review the basic principles for resection of large Olfactory Groove Meningiomas. This is a 61 year old female who presented with confusion. An MRI valuation revealed a large heterogeneously enhancing mass based over the area of the Olfactory Groove. Small Dural tail may be apparent along the posterior aspect of the tumor capsule. There is significant amount of edema associated with this tumor. This tumor was eventually diagnosed as a Meningioma, However, most meningiomas are relatively homogeneously enhancing. This tumor was somewhat heterogeneously enhancing with areas of cystic degeneration. There are various approaches to remove this tumor, including transnasal endoscopic, bifrontel and pterional approaches as well as supraorbital craniotomy via the eyebrow incision. I feel the pterional approach provides numerous advantages over the bifrontal craniotomy, including the fact that the pterional approach does not require violation of the frontal sinuses, does not require a large craniotomy as in the case of a bifrontal approach. And in addition does not require a transection of the superior sagittal sinus. The pterional approach in addition provides a very nice lateral trajectory, for early identification of the neurovascular structures. Therefore, let's review the techniques for the pterional approach from the right side, Sylvian fissure, temporal lobe, frontal lobe. You can see the exposure is primarily based over the right subfrontal area. Gentle elevation of the right frontal lobe exposes the optical carotid cisterns that are opened. The carotid artery, the optic nerve are both identified and the posterior capsule of the tumor is also exposed. You can see the posterior of the Tumor. Now that I see and have identified all the important neurovascular structure, I can be quite aggressive and efficiently De-vascularize the base of the tumor from the anterior cranial base. Importantly, these tumors are primarily mushroom shaped. Therefore the base of the tumor is actually of a smaller diameter than the girth of the tumor Anterior ethmoidal arteries can be quite exuberant and hypertrophied. And during revascularization of the tumor, even Bovie electrocautery may be necessary to control bleeding from the transosseous ethmoidal arteries. The tumor is de-vascularized all the way toward the contralateral roof of the orbit. Here's the part that is especially important in terms of De-Vascularizing the tumor while having their neurovascular structures under direct vision. The tumor is essentially completely de-vascularized, This is a very important step. So the next steps of the operation can be performed efficiently in a relatively bloodless operative field, so that the microsurgical planes are carefully identifiable. So here are the peel surfaces close to the contralateral subfrontal area. So the tumor is completely de-vascularized. Next, I'll go ahead and carefully dissect the tumor from the ipsilateral frontal lobe. As you can see here and coagulate the capsule. Next tumor De-bulking is in order. I like to use a ultrasonic aspirator to decompress the tumor as much as possible. Aggressive De-bulking of the tumor is especially important. Here is the contralateral sub frontal area. I can dissect the arachnoid bands, some of the vessels can also be dissected under direct vision rather than blindly as you dissect the tumor, from the right toward the left side. Piece of the tumor can be removed using scissors. Now the tumor is more mobilized away from the sub frontal area. However, the large size of the tumor requires a aggressive De-bulking for gentle manipulation of the brain for tumor removal. As De-bulking is done, additional pieces of the tumor is mobilized into our resection cavity and the cycle of De-bulking, dissection, De-bulking and dissection continues fixed retractors are minimized or avoided at all cost. Here now the suction is used to hold the tumor away from the neurovascular structures while the aspirator is used to aggressively De-bulk the tumor. That's a very important maneuver. So you can see I park my suction right where there is an important vessel. So I can always have an understanding of the depth of de-bulking as compared to it deep important vessel. Here are some of the easier branches. Now that the branches are identified, I can continue to de-bulk and mobilize the tumor anteriorly. Here you can see again the suction is parked next to an artery at its tip, and then I can be very aggressive to remove the tumor without being concerned about injuring a vessel within my blind operative spot, by means of the ultrasonic aspirator. Only a small piece of tumor is left behind. You can see one of the branches of the ACA is draped over the tumor. Most likely a frontal polar branch. Obviously this branch has to be protected to avoid any post operative schema. Now that most of the posterior pole of the capsule is removed, I'll go ahead and tackle the anterior pole where the tumor is mobilized more posteriorly and all the Adhesions are carefully dissected. Sharpest section is most useful to avoid any avulsion injury to the perforating vessels. Here's the last piece of the tumor. Final result. All the vessels are protected, including their associated branching vessels. Funnel view of our operative cavity. And the postoperative scan demonstrated resection of the tumor without any complicating features. Thank you.

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