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Medial Temporal Lobe Tumor: Anteromedial Resection

March 09, 2015


Here's a case of a medial temporal lobe glioma. 31 year-old male, suffered from a new onset seizures. MRI evaluation revealed a right-sided medial temporal lobe mass with minimal amount of enhancement heterogeneous appearance on T2 weighted images. Since this tumor is primarily within the non-dominant temporal lobe an anteromedial temporal resection followed by amygdalohippocampectomy was conducted. Here's the right temporal lobe Sylvian fissure, temporalis muscle, superior temporal gyrus, middle temporal gyrus, inferior temporal gyrus. Let's go ahead and start with anteromedial temporal lobe resection. Initial corticotomy is located around the crown of the superior temporal gyrus. Here's an anterior temporal vein that can be sacrificed readily since the territory of this vein is being resected. The vein of labbe is situated more posteriorly. Approximately three and a half to four centimeter of the length of the lateral temporal neocortex is resected. Let's review the details for the procedure. The pial membranes are coagulated and sharply cut. Certain landmarks can guide the surgeon regarding removal of the lateral temporal neocortex. Now the neocortex is being dissected. The planar dissection leads to a protuberance at the base of the middle fossa. I'll show you that landmark in a second. First, let's go ahead and continue our dissection toward the temporal tip. Now here is the floor of the middle fossa. A posterior vertical disconnection is being extended toward the collateral sulcus. Here's the thicker arachnoid band there. You can see the thick arachnoid band of that gyrus. It's the floor of the middle fossa, again. I stop at this thick gyral arachnoid band of the collateral sulcus. Our next more important landmark is the protuberance just underneath the temporal lobe. I continue dissection toward this protuberance. The use of this landmark would prevent me to inadvertently open the ventricle and injure the hippocampus prematurely. The lateral temporal cortex is mobilized so that I can continue the plane of the dissection toward the protuberance I discussed a moment ago. Here's the subpial resection method. These pial membranes are also disconnected and cut so that the temporal lateral cortex can be delivered. This temporal neocortical resection will uncap the tumor. That is very evident here. So now I can continue with removal of the mass via a circumferential disconnection. One has to remember the importance of sub-pial tumor removal over the basal cisterns. And here is that temporal protuberance along the middle fossa floor. Let's go ahead and remove the tumor using the sub-pial technique. And here's the pial membranes covering the basal cisterns. Here's the edge of the tentorium. Third nerve should be located somewhere here, obviously should be protected. These tumors often herniate around the edge of the tentorium and place some pressure over the brain stem, may even invade the pial membranes and therefore tumor resection has to be conducted carefully. Here's that third nerve through the pial membranes. The fourth nerve may also be apparent at times along the edge of the incisura. Here's removal of the tumor in the sub-pial fashion. Again, the part of the hippocampus and amygdala affected by the tumor is being evacuated. Here's is choroid plexus. All the resection has to remain lateral to the choroid plexus to prevent any injury to hypothalamus and thalamus. Just small amount of residual tumor lateral to the choroid plexus is being evacuated. Here again, part of the tumor over the pial surfaces of the brain stem are being removed. Thin sheet of the tumor that is left behind over these pial membranes is also being resected. Here's a PCA evidence through the arachnoid bands of the basal cisterns. Here's the brainstem. That's the third nerve evident through the pial membranes. Here's another look of the third nerve. We're now removing the tail of the hippocampus affected by the tumor. Further inspection reveal no evidence of residual tumor that is clearly visible, all the important vessels are carefully preserved. I'm satisfied with the extent of resection here. You can see again, the choroid plexus situated more posteriorly. The third nerve located anteriorly. I worked between the arachnoid bands to evacuate as much of the tumor sub-pialy as possible. And the postoperative MRI demonstrated gross total resection of the mass without any complicating features all the way to the level of the basal cisterns. Thank you.

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