Modified Peri-Insular Hemispherotomy: Multilobar Dysplasia

March 30, 2016


Performance of Modified Peri-Insular Hemispherotomy requires a thorough understanding of supratentorial white matter anatomy. This video relates to performance of such procedure for multilobar cortical dysplasia. This is a 20-months-old boy who developed unfortunately seizures on the fourth month of life. These seizures led to speech development arrest and left-sided hemiparesis. Seizure semiology consisted of eyelid fluttering, left arm jerking and stiffening as well as secondary generalization. The frequency of the seizures increased up to 30 to 40 per day. These seizures lasted 2 to 5 minutes. Three medications were employed without significant relief. MRI evaluation revealed that the right hemisphere was significantly affected by malformation of cortical development, especially the parietal occipital area with the posterior aspect of the hemisphere was significantly affected by the dysplastic changes. An interictal SPECT study revealed significant evidence of hypoperfusion or hypo-activity, affecting the entire right hemisphere. Due to the presence of hemiparesis and significant interference with development, surgical intervention was deemed necessary and since the entire right hemisphere appeared to be affected, a right-sided hemispherotomy was performed. Here's patient positioning, generous curving area incision. Pediatric pins were employed. The right shoulder was elevated to keep the neck in relatively physiological posture. Central line was placed to make sure timely volume replacement in these very young patients, who have very limited blood volume. Following completion of the craniotomy, the first step involves a generous lateral temporal neo cortical resection, eight centimeter of the neocortex from the tip of the temporal lobe is resected. Blood loss is kept to a minimum. There are numerous bridging veins at the floor of the middle fossa, especially along the posterior aspect of the tentorium. There can be a real source of blood loss. The opening within the dura is sealed off using thrombin soaked Gelfoam. Next, the medial temporal lobe structures are also resected. The temporal horn of the lateral ventricle is entered, the hippocampus is un-roofed. The uncus is removed via subpial fashion. The occipital temporal fasciculus is disconnected. I follow the contour of the hippocampus. Ultimately the hippocampus turns more medially to join the area of the Calcar avis. Here's the contour of the edge of the hippocampus. During the next step I remove the uncus subpially. The edge of the tentorium is used as a landmark. The third nerve in the brain stem is protected via preservation of the pial membranes. Now that the uncus is removed, the hippocampus is disconnected and removed and block. I continue that line of disconnection, just lateral to the choroidal fissure, the choroid plexus protected under the retractor blight. Keeping the edge of the tentorium in mind while the hippocampus is being disconnected. The perforating vessels from the PCA to the posterior hippocampus are coagulated and cut. Next, I completed C shaped gyrectomy over the atrium, the body and the frontal horn of the lateral ventricle. I essentially follow the contours of the ventricle, the large transversing or bridging distal ACA branches are carefully protected to avoid hemispheric ischemia after surgery and preservation of the brain blocks to minimize the risk of post operative hydrocephalus. Here's the extent of medial temporal lobe dissection. I'll go ahead and continue un-roofing the as you can see here, and disconnect the overlying cortices. Here's this C shaped gyrectomy, the body of the Corpus callosum. I continue toward the genu of the Corpus callosum. I maintain the dissection just away from the choroidal fissure and the choroid plexus all the way around. Next the Corpus callosotomy is started and the A2 branches or the distal AC arteries are used as landmarks to assure complete callosotomy. Here's one of the A2 branches, more distally, the pericallosal artery it's used as a landmark. Obviously the disconnection has to be complete without placing the contralateral hemisphere at risk. As I move more posteriorly and disconnect the body and splenium portion of the Corpus callosum. I use the edge of the falx as a landmark, since the distal pericallosal arteries are quite small in their caliber, and may not be very effective operative landmarks. Here are the A2 branches within the anterior aspect of the Corpus callosum. Here is the disconnection of the genu of the Corpus callosum all the way toward the foramen of Monro. Here, you can see the turn of the ACA, I stay just short of the foramen of Monro to avoid any inadvertent injury to the diencephalic structures. So here is the use of the A2 branches through the pialed surfaces. Again, following these branches more posteriorly until the edge of the falx is identified. Here's the falx the splenial callosotomy is performed subtotal disconnection of the splenium is one of the most common reasons for an incomplete hemispherotomy and residual seizures after surgery. So now I continue the edge of the falx until I reach their falcotentorial junction, essentially reaching my previous border of disconnection when I performed their temporal lobectomy, I inspect the callosotomy multiple times, making sure that I can see around the edges of the falx, any small overlooked connection can lead to residual seizures after surgery, and then following their route of the Corpus callosum over the falx to ensure complete disconnection. Some of the bridging arteries and branches of the distal ACA are left behind to provide vascularity. Next the frontal tractotomy has to be completed following the edges of the sphenoid wing all the way to the level of the anterior clinoid process. Here is following the route of the sphenoid wing, all the way to the level of the anterior clinoid process. I stay short of the anterior clinoid process to avoid any injury to the ACA perforating vessels. Hemostasis again is secured. Now the lateral cortex of the insular is disconnected while preserving the ACA branches as much as possible. The insulectomy would again, further decrease the chance of post operative seizures. So there's steps involved are the removal of the temporal lobe and the medial structures, a thorough Corpus callosotomy frontal fiber tract disconnection, insulectomy. In addition, disconnection of the corona radiata and the fibers towards the internal capsule during un-roofing of the ventricles. And more specifically the lateral ventricle. Hemostasis is secured thrombin irrigation was used. You can see the final result. Post operative CT scan demonstrates preservation of some blocks of the brain to minimize the risk of postoperative hydrocephalus and superficial siderosis. And this patient made an excellent recovery and has remained seizure-free for about 10 years after his operation. Thank you.

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