December 02, 2015
Let's discuss the technical nuances for a Medial Sphenoid Wing Meningiomas and also describe the techniques for Extradural Clinoidectomy during the exposure. This is a 48-year-old female who presented with a generalized seizure, and on the MRI was found to have a left sided, medially sphenoid wing meningioma. There is minimal evidence of edema, some compression of the medial temporal lobe structures, potentially some mild encasement of the internal carotid artery and some attachments towards the dural anterior clinoid process and also, the posture aspect of the cavernous sinus. I will suspect that the optic nerve is not involved in this case. Although, this possibility cannot be completely excluded unless this area, and specifically the optic foramen is explored during the surgery. So this is a left sided front-temporal craniotomy that's been completed. This is the superior orbital fissure. This is the area of the anterior clinoid. The bone is relatively thin. I'm going to go ahead and move the most medial part of the lateral sphenoid wing or part of the lateral, part of the anterior clinoid using the rongeurs, just to add some efficiency to the procedure. An air drill is used to hollow out the lateral aspect of the clinoid. Now you can see the clinoid itself. A lumbar drain was used at the beginning of the procedure to decompress the dura. Now you can see the entrance of the nerve into the optic foramen. Here in this patient it's pretty obvious. Before I manipulate the clinoid process, I'm going to unroof the optic canal and release the optic nerve to avoid any injury to the nerve during toggling and manipulation of the anterior clinoid process. This is an excellent demonstration of the exposure of the optic foramen through the extradural approach. After drilling the bone until the roof of the optic nerve, is very much thinned out, the last piece or shell of bone is dislodged using a curate. You can see the optic nerve covered by its dura. Clearly here is the clinoid process that has been skeletonized. I'm going to hollow out the clinoid to disconnect it from the optic strut here and the lesser sphenoid wing over in this area. No fixer tractors are used. You can see after hollow out the clinoid. The cortical bone of this structure can be removed and extracted like a tooth. The last piece of it is being mobilized. There's always some bleeding from the cavernous sinus, that can be easily controlled with some gelfoam soaked in thrombin. As long as they bleeding is not arterial, it should not be of any concern. You can actually see the bleeding that is venous from the wall of the cavernous sinus, right in this area. Here's the ball of gelfoam, soaked in thrombin. And a small cottonoid pattie to tamponade the bleeding. Here's the anatomy. You can see the optic nerve that has been decompressed and the air of the clinoid, the bone of which has been removed. Let's go ahead and open the dura now, using a 15 blade knife. I used a dental instrument and the knife to open the part of the dura that is relatively away from me. Brain relaxation is quite desirable using the lumbar drain. The dura is reflected intra laterally. The removal of the bone extradural is important, as early decompression of the nerve. Prevents any injury to the nerve during manipulation of the tumor that could have potentially infiltrated the optic foramen. In addition, it provides an opportunity for extradural devascularization of the tumor during coagulation of the dura along the sphenoidal wing. So here's the dissection of the dura over the anterior aspect of the sphenoid wing. The arachnoid along the are being generously dissected. Here's the arachnoid over the optic nerve. Opening of this arachnoid membranes, obviates the need for fixed retraction. Here's the carotid artery. Optic nerve. The tumor is just approaching the carotid artery, but not invading the optic canal in this case. Here's the magnified view of the tumor, extent of Sylvian fissure dissection. Again, further opening up their arachnoid membranes. The tumor is being mobilized away from the olfactory track. I use a thin piece of cotton over the brain to protect it during movement of the instruments. Here is further opening of the arachnoid membranes. And as expected based on imaging, this meningioma is centered over the dura of the anterior clinoid process. Early devascularization is specially critical to avoid further bleeding during tumor debulking and dissection. Here is the dura over the clinoid that was previously removed. An orbitozygomatic craniotomy is not necessary. This is the posterior clinoid process, and should not be confused with the optic nerve. Here´s the attachment over the anterior aspect of the tentorium. Here again, the clinoid is located here for your orientation. I spent a good amount of time devascularizing the tumor as much as possible from the tentorium. Now that it's devascularized, the capsule is coagulated, cut, and the debulking phase of tumor removal begins. Early identification of neurovascular structures is quite beneficial to keep them out of harm's way. I even use a rongeur rat , sharp one to emulsify the tumor fragments, and then coagulate the capsule to keep it away and shrink it away from the carotid artery. Let's go ahead and remove the tumor piecemeal, into the heart of the tumor, and enucleated, some of the meningiomas can be emulsified using bipolar coagulation. Here's the angle of view, changed slightly towards the tentorium. You can see that just changing the angle of the microscope from anterior to posterior direction will allow us to reach the tentorium, devascularize the tumor thoroughly all the way to the posterior and of its attachment. And here is the third nerve that has been carefully protected doing tumor removal. And, now we have to be careful of the fourth nerve along the tentorial incisura. Here's the membrane of Liliequist. I stay a little bit away from the edge of the tentorium to protect the fourth nerve and avoid its injury by inadvertent coagulation. Just about, underneath where I'm cutting should be the fourth nerve. I´m avoiding coagulation and more of a sharp dissection until the nerve is identified. You can see a peak of it here, just entering the posterior edge of the cavernous sinus. The tentorium looks more normal now, that means that the tumor affected part has been removed. Here is the fourth nerve, that is very safe. In case it is in its arachnoid membrane, here is the magnified view of where we were working and the angle of the view to avoid fixer traction. Now that the dura has been devascularized and mainly debulked, but not all the way, we'll go ahead and start the phase of dissection. See the optic nerve? Here and the carotid artery. Now the posterior communicating artery and the internal carotid artery and their perforators become important to preserve. Here is the posterior communicating artery. And just underneath these arachnoid membranes, I should be able to find the internal carotid artery. Here using sharp dissection to protect the perforators. Here you can see the internal carotid artery, comes in view. Now you can see a branch of MCA that is quite adhere into the pole of the tumor that has to be dissected as well. We'll go ahead and use sharp dissection momentarily to mobilize one of its smaller branches. Right, there that is attached to the pole of the tumor. Here's that branch that's been mobilized. High magnification, use of the mouthpiece. Both of which allow careful dissection, efficiently. Here's the last attachments to this perforator. I used a piece of cotton soaked in papaverine to cover the perforator and relieve its vasospasm after its manipulation. I'll continue to move along the M1 and dissect the tumor away from the artery while preserving all the arachnoid membranes encasing the artery as much as possible. Once I've achieved that goal, let's go ahead and debulk the tumor further, so I can manipulate it and mobilize it away from the mild structures. Here's the anterior aspect of the temporal lobe cortex that is adherent to the tumor. Since the tumor has been mainly disconnected from the medial neurovascular structures, I can be more aggressive and mobilize the tumor into the resection cavity without use of fixed retractors, both along the inferior frontal lobe, as you can see here, and anterior temporal lobe. After the tumor capsule is mobilized away from the brain, it is coagulated and shrunken so that it can stay away from the cortex seize. Some of the veins on the capsule to me, can be quite annoying and challenging. As the tumor is being dissected, these veins, you can pop in the blind spot of the surgeon. Here's further debulking of the tumor capsule. Now I come more anteriorly, make sure that capsule is completely free from the internal carotid artery perforators and the internal carotid artery. You can see I was working inferiorly a few minutes ago. Now I come superiorly as that part of the tumor has been debulked and continue sharp dissection of the capsule away from these vital structures. Again, to enter a carotid artery it's perforating branches, and the posterior communicating artery. Only a beautiful anatomy of the region. The tumor should not be pushed towards the oculomotor nerve, rather debulked to relieve its mass effect before it's aggressively mobilized. You can see the oculomotor nerve that was compressed by the tumor at the depth of our dissection. It's better appreciated here. Looks relatively healthy. The arachnoid membranes are preserved. You can see the perforators. Yeah. Internal carotid artery. Now that the tumor has been further debulked, I'll go ahead and mobilize the capsule away from the inferior frontal lobe and the anterior temporal cortex. Some of the bleeding from the veins on the surface of the tumor should be controlled readily with a piece of cotton soaked in thrombin. Aggressive, blind, coagulation of this region should be avoided. Usually this piece of cotton controls the bleeding readily, as you can see here. The tumor capsules further mobilize into the resection cavity. Next, it has to be further debulked. And I continue the steps of tumor mobilization, debulking to create more space and further tumor mobilization, as you can see here. You can see that the tumor gave away on the last move or maneuver. Here's the tumor that is almost all the way dissected away from the surrounding structures. Now it's further debulked again because I was so disconnected inferior, immediately I was very aggressive superiorly because I knew that the vital neurovascular structures that are along the medial aspect of the capsule are released and therefore protected. Let's go ahead and remove the last pieces. Here it is. Now that the tumor is gone, go ahead and get hemostasis. Here's their membrane of Liliequist. Here's the fourth nerve, third nerve is here. I'm going to coagulate the tentorium affected by the tumor. Here you can see the PCom and the internal carotid artery, the membrane of Liliequist, the oculomotor carotid triangle. I'm going to open the membrane of Liliequist to evacuate the clot in the area of the posterior fossa. This is a typical corridor through the oculomotor carotid triangle to reach the posterior circulation. You can see the contract of third nerve. Here's the base or the apex or bifurcation, the P bones are located in this area. And here's the final product without the use of fixed retractors. The brain looks relatively healthy. Post-operative MRI immediately after surgery revealed collateral resection of the tumor without any complicating features. Thank you.
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