Large Left Insular Glioma: Maximizing Safe Tumor Resection
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- [Dr. Cohen] Aggressive resection of large insular gliomas in the dominant hemisphere, can be quite challenging. Let's review the tenants for such a procedure. This is a 45 year old male who presented with seizures and on MRI evaluation was known to have a large left sided insular glioma with significant frontal extension. On functional MRI imaging you can see that the cortex's responsible for the Broca's area or motor speech or draping over the frontal pole or the superior pole of the tumor. Diffusion tensor sequences demonstrated that the tumor has displaced the functional tracks and more specifically the internal capsule has been displaced medially and posteriorly as expected. I prefer to use the awake craniotomy technique for a section of insular gliomas in general, and more specifically for the ones in the dominant hemisphere. Awake craniotomy is important to map the speech so that a portion of the posterior inferior frontal gyrus can be interred for removal of the frontal portion of the tumor. This is necessary since the transsylvian approach often provides an inadequate operative trajectory for resection of the large insular tumors with frontal or temporal extensions. In other words if the tumor has a significant temporal extension, language mapping is critical. So a portion of the superior temporal gyrus can be entered so additional working channels and operative corridors besides the transsylvian route are available for aggressive tumor resection. So in this patient because of the presence of function over the frontal pole of the tumor and a significant extension of the tumor into the frontal lobe, the motor speech was mapped. Also the language was mapped. So if I need any additional operative corridors, besides the transsylvian route to reach the tumor, those operative routes are available and are deemed safe. Let's review the basic techniques for an awake craniotomy. You can see that the skull clam is placed on the head of the patient as demonstrated. The incision is marked based on neuronavigation data. The draping considers this space necessary for direct communication between the surgeon and the patient, while respecting operative sterility. The scalp flap is reflected anteriorly and left frontotemporal craniotomy is completed. You can see the extent of the tumor beyond their boundaries of their transsylvian route and navigation at just the suture to carefully define the boundaries of the tumor. The orders of the operative steps are as follows. I first dissected seven fissures generously. After the seven fissure is dissected, I proceed with mapping first with face and ultimately with more speech so that I can identify relatively silent areas or functionally silent areas in the posterior in very frontal gyrus that can be accessed to remove the tumor. Additionally, the language was mapped here or the Wernicke's areas. So if I need to transgress the superior temporal gyrus, I can do so safely along the areas that are functionally silent. So multiple dissection or working operative corridors are available for aggressive tumor resection. So let's go ahead and listen to mapping of the Broca's and Wernicke's areas.
- [Patient] One, two, three, four, five, six.
- [Dr. Cohen] You can see the Broca's area and the delaying speech.
- [Patient] In Egypt, we saw the I know what those are called pyramids.
- [Dr. Cohen] So here is their receptive language or Wernicke's area. Super stimulation mapping of the other parts of the superior temporal gyrus and inferior frontal gyrus were also performed to exclude function more specifically in these areas and also in these frontal areas where language was initially noted not to be present. After function has been adequately localized, the Sylvian fissure is further dissected, the M2 branches are followed all the way to the level of M1. Generous dissection of the Sylvian fissure minimizes the use of fixed retraction on their frontal and temporal opercula. Here are the M2 branches dissected distally, the frontal lobe can be quite adherent to the area of the temporal polar and the dissection can be slightly appear at times, sharp dissection is most useful. Here's the medial aspect of the sphenoidal wing. Anterior Sylvian fissure dissection along its sphenoidal segment is followed all the way to the coracoid process and the internal carotid artery at the level of the skull base. Here's M1, here are the M2 branches The entire neurovascular complex is readily identifiable and can be kept out of harm's way during tumor removal. Here's the limen insula. The first step of the operation is the transinsular route for removal of the tumor located primarily in the region of the insula. The pre insular sulcus along the frontal region is quite adherent. The working channels between the MCA branches are created and the tumor is removed piecemeal. Tumor is relatively soft at portions of its poles. Here you can see the M2 branches are carefully spared. Some of their finer perforating vessels to the insular itself are sacrificed. Here's additional tumor removal, along the superior pole of the glioma using dynamic retraction of the suction device, neuronavigation guides every step of the resection. Now I divert my attention to the area of the peri insular sulcus. This sulcus is much more defined and readily dissectable from the temporal lobe because of the presence of the MCA branches within the inferior peri insular sulcus. You can see that that bipolar forceps for the lack of better word, emulsify the tumor and the suction removes the emulsified tumor away from the resection cavity. Here's that emulsification process. Ultrasonic aspirator is also quite effective for the more fibrous part of the tumor. MCA branches are kept out of harm's way. One has to remember the location of the lateral lenticular straight arteries that are somewhat predictable during dissection of the distal M1. Now I work underneath the MCA branches and between those working channels initially created here is mobilizing the frontal pole of the tumor just underneath the frontal opercula. This part of the tumor appear to be very fibrous. You can see how the suction device mobilizes the normal brain while the tumor is pulled into the resection cavity. You see two working channels between the MCA branches that are exploited for removal of the tumor. The blind spot on the surgeon is really underneath the opercula, where the tumor can be frequently left behind. The brain is looking now a little bit more normal, although there's still some residual tumor in this area. can be quite effective. You can see the discoloration of the tumor. Now that the tumor is removed within the Sylvian fissure and insula while maximizing the operative corridor through the working channels of the transinsular route. I complete a corticotomy about one gyrus anterior to the Broca's area and further achieve a more expanded operative corridor to remove the frontal pole of the tumor. I continue to intermittently work between different working channels while the tumor is descending into the resection cavity. Here's another working channel more anteriorly along the insula that's being created. So the tumor along it's anterior pole can be removed. Now, this is the more posterior part of the tumor within the insula that is being mobilized into the transinsular corridor. One has to be very careful while using the ultrasonic aspirator close to the MCA branches. The vasculature is kept away from the tumor during its evacuation using the ultrasonic aspirator. Again, one of the important pitfalls into surgery is carefully dissecting the tumor beyond the boundaries of the transinsular or transsylvian approach to be able to achieve adequate aggressive resection, to justify performance of the procedure. Here you can see one of the long M2 branches that is headed toward the motor cortex that should be carefully protected. Any vessel heading toward the motor cortex has to be carefully preserved and only find perforating branches staying within the insula are coagulated and cut. You can see the MCA bifurcation, the frontal M2, working between the transvascular channels or intervascular channels to remove tumor. Now that the tumor is further debarked internally, posteriorly, the capsule of the tumor is being mobilized into our resection cavity. This maneuver prevents aggressive retraction on the functional cortices along the posterior inferior funnel and posterior superior temporal gyrus. Here's the emulsification process of the tumor via the bipolar forceps. Essentially the forceps are used as scissors. The more medial part of the tumor appear to be very fibrous. Others lead this area specially important as they lateral lenticulostriate arteries could be transversing it. And also the internal capsule apart set more posteriorly. Here's the more discolored tumor that's been removed compared to the pre tumoral area. I continue to debulk and mobilize the tumor into the transinsular corridor. The tumor within the temporal lobe is also being removed until normal brain is encountered. You can see the working channels that have been exploited around all the branches to achieve resection. Postoperative MRI in this patient demonstrates more than 80% resection of the tumor. This patient did not have any neurological deficits by the end of the operation. However, developed some seizures and speech difficulty after surgery. These deficits resolved within two weeks after the operation. This is an important principle that if the patient continues to remain stable neurologically by the end of the resection. However, it deteriorates the day after the operation, the prognosis of recovery is excellent. However, if there's any new deficits developing by doing the operation, most likely the causality ischemic and the chance of recovery is much less. They're important lessons involved with removal of these tumors, including that you self mapping to allow safe transgression of cortices around the functional areas to allow aggressive removal of the tumor. Obviously the transinsular approach or the transsylvian approach is inadequate to expose the poles of the tumor and subtotal resection may not justify the risks of the surgery, if resection is less than 60% of the original tumor. This patient has since made an excellent recovery and has returned to work. This residual tumor has remained stable on MRI examination two years after surgery. Thank you.
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