Insular Temporal Low Grade Glioma: Mapping

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[Dr. Cohen] Let's talk about maximizing resection of gliomas near the eloquent cortices including low grade gliomas within the dominant temporal lobe invading the insula. This is a young patient who presented with generalized seizures and subsequent who went to MRI evaluation. And as you can see on the MRI, there's a large T2 signal, hyperintense mass, extending to the level of the posterior temporal horn and also reaching the level of the insula. This tumor was suspected to be a low grade glioma, mapping deemed necessary due to the extent of the tumor within the dominant temporal lobe. I prefer the use of regional scalp anesthesia, obviously injecting the occipital, supraorbital and supra troll clear nerves. The patient should be very comfortable and be able to swallow easily. You can see the generous scalp incision guided by neuro navigation. Draping allows easy communication between the surgeon and the patient. A generous left front of temporal craniotomy was elevated the margins of the tumor based on MRI neuro-navigation are marked with a dark suture. You can see that the tumor does extend posteriorly and can place the Wernicke's area at risk. I usually attempt to remove as much of the tumor as possible, first through an intramedial temporal lobectomy and potentially the transsylvian approach. However, sometimes a transcortical corridor via the inferior frontal gyrus may be necessary to remove the frontal component of the tumor, therefore mapping of their language and motor speech areas is both necessary. Importantly, the mapping of the language area will determine the safe borders for a lateral neocortical resection in the temporal lobe to access the posterial border of the tumor. Let's go ahead and map that Broca's face, as well as Wernicke's areas.

[Patient] Two, three, four.

[Dr. Cohen] There's one

[Patient] Yeah. Five, six, seven, eight.

[Dr. Cohen] Let's map the face. Here you can see the twitch in the face. Often the face should be mapped first, before we go to the motor speech. However, in this patient it was more readily possible to map the motor speech first. Let's map the Wernicke's area.

[Patient] This is a crocodile.

[Dr. Cohen] You can see the Wernicke's area that somewhat over lies the poster board, the tumor. However, in this situation, I'm going to spare about at least a centimeter of the cortex, anterior to the Wernicke's area, and then undermine the cortex and remove the tumor. This should be relatively safe. As long as this undermining does not place the functional courtesies under significant retraction. Here's the intramedial temporal lobectomy, it has most of this tumor is really temporal in origin. You can see I left at least a centimeter of intact cortex in front of Wernicke's area tumor is relatively soft. The emcee branches are carefully protected as tumor excision continues. Here you can see the temporal horn that was exposed and the undermining maneuver was used to remove the poster board of the tumor without affecting the overlying functional cortical areas at risk. The frontal component of the tumor was also removed by elevating the funnel lobe, and again, undermining and working underneath the functional cortices without placing them on their significant attraction. These maneuvers led to acceptable resection of this tumor. This patient had a normal neurological examination at the end of the operation and mapping procedure. However, on the first post-op they developed some minor speech difficulty, that resolved on the second week of post operative period. These delayed neurological deficits are most likely subclinical seizures. I usually make sure the patients are supported on supratherapeutic levels of anti convulsant medications during the preoperative period. Thank you.

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