December 16, 2015
Let's review another case of a non-dominant insular glioma, and describe the techniques for using mapping for advancing safe gross, total resection of these tumors. This is a 32 year old male who underwent subtotal resection of his right-sided insular glioma, and was transferred to our institution within a week of his surgery for more aggressive resection. This is the preoperative MRI before my operation. And you can see the location of this insular glioma, which is mainly frontal. The extensive tumor reaches the lateral pore of the putamen as expected in these tumors. The tumor does have a cystic component along its medial pole, which makes the resection more easy. You can also see on the sagittal images, the location of the mass, primarily within the frontal area and the insular area. Therefore, one can categorize the tumor primary in primarily frontal with some insular extension. I prefer resection of insular gliomas both in the non-dominant or dominant hemisphere, under wake conditions. Many of my colleagues prefer resection of non-dominant insular gliomas under sleep conditions. My rationale for using the awake condition is the fact that mapping with a patient awake is more reliable. And specifically during the posterior pole of the tumor where the internal capsule, can be quite near the resection cavity. The use of awake techniques for subcortical mapping is most likely more reliable. In addition, the awake patient can provide immediate feedback regarding his or her neurological status. These factors have led to more aggressive resection is in my hands in regards to insular gliomas. So here's the previous incision, which was primarily a tentorial incision. I "T-eed" off the incision for more posterior exposure to be able to reach the pole of the tumor close to the internal capsule. Patient is awake under conscious sedation. The initial exposure is performed with a patient under deeper sleep conditions. You can see the previous area of dissection from the first index operation. The insular areas exposed via this section of their sylvian cisterns. Initially, I use cortical mapping to locate the face area so that I can identify safe areas within the posterior inferior frontal gyrus to perform corticonomies for resection of the portion of the tumor, which is primarily within the frontal area and more posteriorly. The transsylvian approach provides adequate resection of tumors, which are confined to the mid portion of the insula. However, tumors that have significant frontal components such as the one described here, require corticonomies within the posterior inferior frontal gyrus for their aggressive resection. Therefore, the face areas identified so that this area and about a centimeter anterior to this area is protected during performance of the corticotomy within the posterior inferior frontal gyrus. Let's go ahead and do the mapping. You can see their face twitched. As I stimulated in the area marked with face. Here's the inferior frontal gyrus that is expanded into the sylvian cisterns, The M2 branches are carefully exposed. The dissection of the fissure is extended as posteriorly as possible. You can see that the tumor has extended itself into the fissure. Here's the X ten of seven fissure dissection using navigation. I assure myself that the ceiling of the dissection has exposed portion of the insula just about posterior to the pole of the tumor. Now the tumors entered all the MC branches are carefully protected. The opercular branches are also protected. Now that the transsylvian approach was used to remove as much of the insular component, a corticotomy within the posterior inferior frontal gyrus was performed to evacuate the predominantly frontal component of this tumor. All the traversing opercular branches are carefully protected and working channels are created in between them for removal of the tumor as you can see here. So that ischemia in the distal territory of these opercular vessels is avoided. You can see the posterior extent of resection. This is an important finding that I like to emphasize here. You can see the knot-make appearance of the basal ganglia, which is the most medial aspect of our resection on intraoperative neuronavigation. You can see that this corresponds essentially to the lateral part of putamen and basal ganglia. Also lenticulostriate arteries can be identified at this border. These branches should be carefully protected and aggressive coagulation around these very fine vessels should be avoided to prevent their sacrifice. This is the final resection result. The face area was located here. You can see a gyrus anterior to it was preserved. The opercular vessels coursing through our operative corridor within the inferior frontal gyrus were protected. And both the transsylvian and the transcortical trajectories were used for gross total resection of this mass. Subcortical mapping was used for a section of the pole of the tumor more posteriorly. Post operative MRI demonstrated gross total resection of the tumor without any complicating features. Thank you.
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