Medial Sphenoid Wing Meningioma: Principles of Resection
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This lengthier video describes the tenants and basic principles for resection of large medial sphenoid wing meningiomas. This is a 25 year old female with right-sided visual dysfunction, CT scan demonstrated a large meningioma, primarily centered over the medial aspect of the sphenoid bone leading to some hyper stasis in the area of the sphenoid wing and posterior wall of the orbit. MRI evaluation confirmed our findings in a relatively homogeneously enhancing mass along the medial sphenoid wing with significant hypertrophy and high parostosis of the medial sphenoid wing, minimal amount of edema was present. You can see the MC branches are draped over the medial and superior pole of the tumor. Here's the right sided frontal temporal craniotomy, the frontal lobe, the temporal lobe, the dura over the Sylvian fissure. The lateral spheroid wing was aggressively drilled away. In addition to the posterior wall of the orbit, you can see the bone is relatively soft, but definitely a hypertrophied. Further bone removal extended more medially. You can see some of the bone removal around the roof of the orbit. I performed an extradural clinoidectomy in this case, as I want it to decompress the optic nerve as early as possible. So the nerve is not placed under any traction, during manipulation of the tumor intradurally. Here you can see the nerve, again, this time the clinoidectomy is quite challenging because the tumor has led to significant hypostasis of the bone in the area of the clinary process. After performance of the clinoidectomy and generous decompression of the optic nerve, the dura was open in a curvilinear fashion. The anterior aspect of the Sylvian fissure was dissected and the tumor was de dressed. Next, I find the MC branches located within the fissure, just along the posterior capsule of the mass. Here you can see some of the M2 branches. There early identification keeps them out of harm's way. The tumor is not de bulked yet. Although part of the tumor was de vascularized during our extradural bone work. Again, the margins of the tumor are better defined. You can see a more demagnetizing view of our operative corridor. Next I divert attention to further de vascularize the tumor along the dura of the sphenoid wing. Devascularization also continues along the base of the frontal lobe or anterior cana fossa, next the tumor is entered and further de bulked. So it's manipulation is safely possible. Here's the disconnection of part of the tumor anteriorly. Again, one has to be careful not to injure the optic nerve located just medial to the anterior capsule of the tumor. Here's the olfactory nerve. The part of the dura of the intercranial fossa is heavily coagulated. You can see, I continue to follow the contour of the sphenoid wing to de vascularize the tumor. Cottonoid patties are used to gently mobilize the tumor in the brain. You can see that the tumor is very thoroughly de vascularized all the way to the area of the interior clinoid process. Next further debulking is necessary before the capsule of the tumor can be effectively dissected away from the MC branches. You can see the suction device pulls the tumor away from the brain, so that aggressive and safe decompression and enucleation can be accomplished. The capsule is also shrunken using bipolar cautery so it can be held away from the brain. I continue tumor debulking piecemeal. This is a relatively large tumor and therefore ample amount of debulking is necessary before the neurovascular structures can be dissected. The more fibrous or partially calcified parts of the tumor were removed using micro scissors. Here's the more anterior pole of the tumor days being dissected away from the frontal lobe. Now I divert my attention to the posterior capsule, where the MCAs are the center of attention and a surgical target. Here's an M two branch draped over the posterior pole of the tumor, part of this branch was readily mobilizable away from the tumor capsule without the need for significant dissection. Sharp resection is specially important for parts of the vessel that is very adherent to the posterior part of the capsule. As more of the vessel is mobilized, further debulking of the tumor is mandatory. Scissors were used to cut a big piece at once. Ultrasonic aspirator further assists with removal of the center of the tumor that in this case was relatively fibrous. Only a thin shell of capsule is left behind so that the capsule can be dissected away from the neurovascular structure in a very flexible manner. As part of the Sylvian portion of the tumor is removed, the temporal part has to also be de bulked so that the entire capsule of the tumor can be readily mobilized away from the neurovascular structures. I believe the key maneuver is careful debulking, aggressive de bulking so that the capsule can be effectively mobilized, microsurgical planes identified, and neurovascular structures protected. Here is part of the tumor that was invading the pia of the temporal lobe. A piece of cotton is used again to protect the brain from the force of the suction device. We're getting close to the MC bifurcation, Gentle mobilization of the adhesions to the posterior capsule of the tumor is apparent, piece of cottonoid may be used to again, protect the pia from the effect of the suction device. Another piece of the tumor is resected. Here's the M one branch, the MCA bifurcation, again, you can see the notch within the posterior capsule of the tumor created by the M one. Here's the dissection of the tumor from the medial anterior temporal lobe. This is another important maneuver. You can see the tumor is being divided in half along the axis of the M1. This maneuver is conducted as I get closer to the skull base and further easy mobilization of the capsule is now possible due to the bulk of the tumor and the location of the artery into the mid portion of the mass. So I follow the route of the artery under direct vision. I transect the tumor and continue tumor division toward the skull base. Now that the portion of the tumor is removed I use bipoloid cautery to further de-bulk the tumor. Here is further decompression and dissection of the vascular structures. Any small perforators that are engulfed into tumor have to be protected and a piece of tumor left behind over them as significant manipulation of the perforating vessels, including the vessels off of the anterior carotid artery and picom are easily injured and damaged during dissection. I'm not facing any number of perforators at this juncture. Therefore, I continue my aggressive tumor resection, heparin soaked cotton pledgitts, may be used to maintain the dissection planes and relive vasospasm from the vessels that are being manipulated. Further, debulking is required so that the tumor capsule can be mobilized. The part of the tumor days invading the lateral wall of the cavernous sinus is left intact. Here you can see I'm getting close to the base of the skull base. The tumor is being removed from the artery. One of the most important steps is the compression of the optic nerve in this case, obviously the artery is just on the other side of this portion of the tumor. So I'll go ahead and aggressively debulk this piece so I can rotate the tumor anteriorly away from the artery, and also hope to find the optic nerve. The portion of the dura that is affected by the tumor is being resected. I was unable to find the optic nerve readily before further coagulation was performed in that area. Therefore I entered the optic canal through the area of the clinoidectomy. Found the nerve more distally and followed the nerve proximally toward the chiasm. You can see how the tumor is within the optic canal. Compressing the tumor significantly. A blunt hook was used to deliver the tumor out of the canal. In this case, the nerve was mobilized inferiorly by the tumor. And I was unable to see the nerve early on during dissection of the posterior part of the capsule. And that is why I found the nerve within the foramen where I knew the nerve is definitely localizable. I didn't want to bluntly or blindly dissect around the posterior capsule without knowing where the nerve is. You can see the nerve is now very nicely decompressed. The part of the dura medial to the nerve affected by the tumor is also being removed. The optic foramen and is being further decompressed. It's roof is thoroughly removed. Since the foramen is already decompressed and evacuated I can use small tipped Paris en rou jour to safely un roof the nerve. Additional portion of the tumor over the dura of the tumor, of the obcello was resected. The contralateral optic nerve and carotid artery are apparent. They are not effected by the tumor. Here is inspection of the edge of the tentorium. You can see a portion of the tumor effecting the cavernous sinus was left behind, the dura of the anterior middle fossa was curated away to decrease the risk of future tumor occurrence. Here, you can see again, the optic nerve and the canal thoroughly decompressed. Caesium, the carotid artery portion of the tumor infiltrating the cavernous sinus, frontal view of our operative cavity. In this case, the postoperative MRI demonstrated complete removal of the tumor without any complicating features, thank you.
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