Olfactory Groove Meningioma: Basic Techniques
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Let's review some of the basics for resection of olfactory groove meningioma. This is a 50-year-old male with progressive personality change, who suddenly suffered from a seizure. MRI evaluation reveals a giant olfactory groove meningioma with significant evidence of edema and geography also localized as the location of their orbital and frontal polar arteries, draped over the superior pole of the tumor. He underwent a left pterional craniotomy. I like to place a lumbar drain at the beginning of the procedure. Minimal amount of CSF is removed, due to mass effect of the tumor. However, up to 50 or 60 CCF, CSF is removed in 10 CC aliquots, during dural incision, so that adequate brain relaxation is attained. Here you can see the generous pterional incision, toward the contralateral mid-pupillary line. The craniotomy is mainly frontal, exposing the frontal lobe. You can see the extent of the craniotomy almost to a level of the midline and the left side. I like to use the unilateral extended pterional craniotomy, rather than a bi-frontal crainiotomy for resection of large or giant all factor groove meningiomas. This unilateral craniotomy, minimizes the risk of violating their frontal sinuses, also avoids bilateral frontal manipulation. And in addition, I'll use early identification of this cerebrovascular structures, including the optic nerve and carotid artery, through a lateral subfrontal trajectory. Here you can see the section of the sylvian fissure, left frontal lobe, left temporal lobe and the optic nerve and carotid artery are identified, very early on and therefore protected. Here's the optic nerve carotid artery, reaching this tumor via bifrontal, subfrontal trajectory, always leaves the surgeon guessing about where the exact location of these important cerebrovascular structures are, since these structures are along the most posterior aspect of the tumor. In other words, the tumor places the surgeon, away from the cerebrovascular structures, via their bilateral frontal craniotomy. Here's the base of the tumor, the lumbar drain provided very nice relaxation for the cerebrum. Now I can effectively devascularize the tumor, early on without it's significant debulking. This early thorough devascularization of the tumor base is a key factor to minimize blood loss, maximize efficiency and keep the operative field clean, during the microsurgical part of the operation. Part of the tumor was devascularized, as you can see here. However, I wanted to achieve additional brain relaxation, so a piece of tumor that was devascularized was removed, via micro scissors. Ultrasonic aspirator devices may also be used. If the lumbar drain was not installed the brain would be relatively tight. Placing the frontal lobe at significant risk of retraction injury. Now more tumor fragments are removed. The tumor is enucleated from within. You can see a minimal amount of blood loss because the tumor was so effectively devascularized along its base. Aggressive debulking is a key maneuver for mobilization of the tumor capsule from the cerebrovascular structures, as you can see here. I mobilized the capsule into the resection cavity, while using the cottoniod paddie to gently wipe the brain whose PI has been violated, as expected from their evidence of significant edema on preoperative MRI examination. Any vessels adherent to the surface of the tumor, which are en-passage, are carefully inspected and dissected. Any vessel that is entering the tumor has to be sacrificed. Further debulking was accomplished. Small vessel entering the tumor is coagulated and cut. Gentle mobilization of the tumor, avoids any risk of avulsion injury to any of the vessels. Sharp dissection is the best method of dissection, when possible. Next, this piece of a tumor that has been mobilized is resected, piece of cottoniod is used to maintain the planes of the section. Here's the optic nerve. All the arachnoid planes are carefully respected. The arachnoid bands are left on the cerebrovascular structures. Sharp dissection is mandatory over these areas. Any perforating vessels from the ACom or A2's are strictly protected. You can see this small vessel was thoroughly isolated, before it was sacrificed. Here's the contralateral optic nerve. I use the arachnoid bands as handles to mobilize the arachnoid, toward the cerebrovascular structures and away from the tumor capsule. Thicker arachnoid bands are disconnected, and now the tumor is readily delivered. You can see all the Adhesions to important cerebrovascular structures were first disconnected before the tumor was mobilized. Some of the A2 branches are apparent here. Fortunately, this tumor was not very adherent, to the A2 branches and their corresponding perforating vessels. The frontal orbital and orbital frontal arteries, over the capsule of the tumor are preserved to avoid post operative ischemia. Aggressive suction over the perforating vessels in the area of their super charismatic and hypothalamic regions are avoided. Irrigation is used to clear the operative field. These perforating vessels are quite sensitive to the force of suction. You can see gentle mobilization of the arachnoid bands away from the tumor capsule. Small piece of the tumor will be ultimately also extracted. Small piece of cotton is used to avoid the direct force of suction on the structures. Here are the final steps in remove all the tumor from the contralateral subfrontal region. Again, using the arachnoid bands, as the guiding principle of planes off the section. And in this case, postoperative MRI demonstrated gross to a removal of the mass without any complicating features. Thank you.
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