January 27, 2016
Let's review the technique and indications for the transsylvian selective amygdalohippocampectomy. This is a 45-year-old male who presented with partial seizures, and on MRI evaluation, was diagnosed with a right-sided uncal or amygdala, as well as anterior hippocampal tumor. This tumor ultimately was diagnosed as a low grade glioma. I use the transsylvian selective amygdalohippocampectomy primarily for anterior hippocampal and amygdala lesions. I believe the reach of the transsylvian approach toward the posterior aspect of the hippocampus is somewhat limited. Therefore, if the lesion reaches the tail or poster segment of the hippocampus, I use the anteromedial temporal lobectomy approach to expose the temporal horn and reach the posterior aspect of the hippocampus. More specifically, I attempt to use the transsylvian approach for dominant anterior hippocampal, and uncal or amygdala lesions. Let's go ahead and review the techniques here. And right-front temporal craniotomy was completed. Standard curvilinear incision was used. The head of the patient is turned about 30 degrees temporal lobe, frontal lobe, Sylvian fissure is widely dissected and split. I use Jeweler forceps to open the superficial thick arachnoids bands. Next, the spring action of the Bipolar forceps are used to expose the deeper aspects of the fissure. You can see the MCA's being mobilized so that the inferior or limiting parainsular sulcus is exposed. Here is temporal polari. Here's the limen insula. The first corticonomy is guided based on our navigation and essentially is lateral to the perisylvian vein and most commonly lateral to the intertemporal or temporopolar artery. Using neuronavigation I remove the part of the uncus and amygdala until their achnoid bands, over the ambient cisterns are exposed. Here you can see the sub-pial resection technique. Obviously the arachnoid bands are carefully protected. The third nerve is apparent at the edge of the tentorium. You can see the extent of a resection just posterior to the amygdala. Next, I remove the anterior part of the hippocampus or pes hippocampus while exposing the temporal horn. Choroid plexus is identified and the dissection continues just lateral to the choroid plexus. Here's the inferior choroidal point. Here's choroid plexus, just barely visible at the tip of the arrow. Now I continue to remove the anterior part of the hippocampus again, in this uphill fashion. Now you can see just my resection and the PCA through the arachnoid bands on the perforators to the posterior hippocampus are quite apparent. The dissection is kept just lateral to the choroidal fissure. Here's the neuronavigation data. Again emphasizing my resection reaching just to the posterior aspect of the tumor. All of the blind spots in this surgery is just lateral and underneath the middle temporal gyrus. You can see that microsurgery preserves most of the temporal lobe in this transsylvian approach, as long as dynamic retraction is used and fixed retractors are avoided. Here's the operative corridor. The MCA branches are quite manipulated during this approach. And I often use Papaverine-soaked cotton to bathe these vessels periodically during the surgery. Again, due to manipulation of these vessels, I do believe the risk of this procedure is slightly higher than anteromedial temporal lobectomy and amygdalohippocampectomy. Moreover their seizure outcomes have not been proven to be significantly superior to those of the anterior temporal lobectomy approach. The neuropsychological outcomes also may not be different between the transsylvian approach versus the anterior temporal lobectomy approach. Here again is another view around the vascular structures and the postoperative MRI demonstrates a reasonable resection of the tumor in the reach torward the posterior aspect of the hippocampus and its tail is somewhat limited. Thank you.
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