Olfactory Groove Meningioma: Extradural Clinoidectomy
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This is a detailed video, describing technical nuances for resection of olfactory groove meningioma via the transcranial approach. This is a 60 year old female who presented with progressive left sided visual decline and was diagnosed with this olfactory groove meningioma. There is minimal evidence of edema. However, the tumor is extending more posteriorly and most likely herniating through the optic foramen. Patient underwent a left front temporal craniotomy. The left vision was affected more significantly. Lumbar drain was installed at the beginning of the procedure and an extradural clinoidectomy was initially completed so the affected left optic nerve, is immediately decompressed. You can see some hyperostosis of the bone over the optic canal and at the level of the clinoid process. Here is this the sphenodial fissure here's the optic nerve through it's foramen The clinoid process is also drilled away. Here you can see the dura over the optic nerve, the clinoid process. Complete clinoidectomy was accomplished. The typical venous bleeding during mobilization of the clinoid process was controlled using, gel foam powder soaked in thrombin. You can see the optic nerve, the area of the clinoid process. Next, the dura was open in curvilinear fashion. The tumor was immediately encountered at the level of the anterior cranial fossa. You can see the optic nerve significantly affected by the tumor and pushed more posteriorly. Here is a more magnified view of the left optic nerve, displaced and compressed the tumor. Here's the olfactory nerve. This patient did have relative intact olfaction before surgery and the goal was at least to preserve one of the olfactory nerves during dissection. I first devascularized the tumor along the intercranial base, working around the olfactory nerve to completely disconnect the base of the tumor, bleeding from the ethmoidal arteries or the transosseous feeders can be quite vigorous. And I may even sometimes use, the monopolar electrocautery to control the bleeding from the bone. I continue devascularization and disconnection of the base of the tumor all the way to the other side. Here is the other side of the anterior cranial base. Next, the falciform ligament was transected so that the optic nerve, can be generously decompressed further. You can see the area where the falciform ligament, was pinching the nerve leading to a discoloration. After the nerve was decompressed, it can be gently mobilized and the tumor is dissected away from the nerve. The tumors devascularized at the area of the tuberculum sellae. Next, the tumor can be debulked and dissected. Here is the anterior capsule of the tumor. Here is the debulking process. The ultrasonic aspirator can be quite effective. Note the use of dynamic retraction working on both sides of the olfactory nerve. Now that the tumor is further debulked, the bulk of the tumor can be mobilized away from the nerve without manipulating the nerve itself. Again, some bleeding was encountered from the ethmoidal arteries and controlled effectively, using the monopolar electrocautery. irrigation is used to avoid transfer of the heat to the optic nerve. Here's more debulking of the tumor. Now, the tumor is allowed to descend into our resection cavity, this is a relatively operative blind spot and the anterior cerebral arteries should be protected. Parts of the tumor were quite fibrous. Here's mobilization of the tumor away from the chiasm. Internal debulking allows more flexible mobilization of the tumor capsule. And here's the chiasm, the tumor capsule. I continue to follow the capsule away from the chiasm and as you can see away from, one of the A1 branches. And here's the chiasm pushed more posteriorly by the tumor. I follow the capsule until the contralateral proximal optic nerve, is identified. And then I continue to dissect around the superior pole of the tumor as well. Here is mobilization of this superior capsule from one of the ACA branches. All the ACA branches have to be carefully protected. Here's the contralateral optic nerve. Here's a branch of ACA draped over the superior pole of the capsule. Here is again the contralateral optic nerve coming in close contact to the contralateral part of the capsule. The part of the tumor that was herniating into the medial part of their contralateral optic foramen, was removed so that the contralateral nerve, can be generously decompressed. Here is adherence of one of the ACA branches to the superior capsule of the tumor, sharp dissection was used to spare the artery. Here is a large piece of the tumor that was resected. Again, I focused my attention so that most of the tumor, affecting the contralateral optic nerve is removed. The foramen is inspected. Now, that the contralateral nerve is taken care of, I'll go ahead and decompress the ipsilateral nerve. Here is the ophthalmic artery moving into the optic foramen, this artery should not be mistaken with residual tumor and injured. Various sized curettes, are used to curette the dura over the tuberculum sellae to maximize tumor resection. Again, the contralateral optic foramen is further inspected to make sure there is no obvious, presence of tumor in the origin of ophthalmic artery contralaterally. Here is the olfactory nerve that remains intact. Papaverine soak gel foam was used to relieve spasm of the ACA branches. The ipsilateral optic nerve, was also generously decompressed. You can see removal of the tumor from the medial part of the ipsilateral optic foramen. No residual tumor is apparent, compressing the ipsilateral nerve. Here is the funnel resection cavity, brain appears relatively healthy. Another final view of the decompressed optic nerves and the postoperative MRI at three months revealed, good resection of the tumor and this patient's left vision improved after surgery. Thank you.
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