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Lateral Pontine AVM

December 02, 2015


Let's review the intraoperative events for resection of a Lateral Pontine Arteriovenous Malformation. This is a young man who presented with spontaneous intraventricular hemorrhage, and is subsequently underwent further evaluation, which revealed a small arteriovenous malformation located just lateral to the root entry zone of the trigeminal nerve, on the left side. The drainage pattern was primarily going a lateral and slightly superiorly, potentially leading to the superior petrosal sinus. Patient underwent a left sided Retromastoid Craniotomy. You can see the extent of bony exposure to mastoid bone that has been well waxed. The transverse sinus as well as the sigmoid sinus were generously on roofed, so that a more lateral trajectory towards this Cerebellopontine angle, can be achieved. The edges of the dura were gently retracted using retention sutures. And I started our dissection around the cerebellum, following the petrotentorial junction. Lama drain was performed, at the beginning of the operation to further relax the cerebellum and allow smooth movement, around a cerebellum effortlessly. You can see the elevation of the dural edges provides just a few more millimeters and may decrease the amount of cerebellar retraction. Silver opera dam was used to slide the cartinoid over the cerebellum. Here's the dura, the petrous bone. Go ahead and reposition our cartinoid, making a slide over the cerebellum, using the rubber dam. Here's the petrotentorial junction tentorium dura of the petrous bone. You can see the operative trajectory towards the CP angle. Here we're a slightly more toward the petrous side. The arachnoid bands over the CP angle are dissected. Additional CSF, is released, leading to much needed brain relaxation. My first goal would be to find a trigeminal germinal nerve. It is an excellent landmark for identification of the nidus. The lateral Pontin Artevenous Malformations are just lateral, to the root entry zone of the trigeminal nerve. Here's the eighth cranial nerves. Brainstem auditory evoked responses were monitored in this patient. All the arachnoid bands around this complex are released to avoid any traction on the eighth cranial nerve. The normal appearing superior petrosal sinus here, which was very dark is transected. So additional space can be provided for cerebellar mobilization. You can see the arterialized vein here from the surface of the cerebellum leading to the tentorium. Next the root entry zone of the trigeminal nerve is very carefully isolated. All the arachnoid bands are widely opened. Prior history of hemorrhage in scerio may leads to some scarring. You can see another relatively normal appearing vein entering the petrotentorial junction. The root entry zone of the trigeminal nerve is not yet in view. I continue to open the arachnoid bands. Here is a branch of the superior cerebellar artery. Here's moving slightly within their super cerebellar corridor. The fourth cranial nerve is identified at the edge of the tentorium. Any suspicious arterialized vein is obviously protected. So now, I start more laterally where the malformation joins their surface of the cerebellum, and continue to disconnect the margins of the malformation. Here's the exact root entry zone of the trigeminal nerve. Here's the arterialized vein. I continue to disconnect the malformation and state epi-peel. In other words, I will not violate the surface of the P of the brain stem. And if there's any smaller residual nidus within the brain, coming off their brain stem. I will leave that small residual alone. So I continue disconnecting the nidus within the epi peel space. I continue dissection very close to the peel surface of the brain stem. Some bleeding is encountered here. Very discriminate coagulation is used. Here's the draining vein of the malformation. Here's the nidus. Here's where the nidus comes in contact with the root entry zone of a trigeminal nerve. There is no additional nidus, just around or medial to the root entry zone of the trigeminal nerve. Patience is required for managing bleeding at this stage of the operation. Often the initial bleeding can lead to more aggressive bleeding later. Here, I continue to dissect the base of the malformation away from the root entry zone of the trigeminal nerve. Some of the feeding vessels from the superior cerebellar artery or a parent, they are immediately on the surface of the malformation. Here's additional bleeding from the inferior surface of the nidus. I continue to gently coagulate the feeding vessels and potentially use gel foam with thrombin to pack the bleeding point. Obviously the dominant draining vein is protected at all times. This part of the video is minimally edited. So the viewer can review the details associated with managing the bleeding at this critical part of the operation. So the bipolar forceps are cleaned. And I continue to gently disconnect the base of the malformation from the entry zone of the trigeminal nerve. As I continued to disconnect the details and the feeders at the base of the malformation, you can see the draining vein started to appear much darker. That means, at least, a reasonable portion of the malformation is disconnected. Now, I continue this connection of the malformation in more superiorly, laterally. Bleeding is more under control, and the draining vein appears relatively dark. So here is, additional phases of dissection, just lateral to the root entry zone of the nerve. Again, I emphasized the epi-peel nature of the dissection. Any intra-peel dissection is prohibited. Here's the portion of the nidus, located more superiorly, also slightly infiltrating the petrosal surface of the cerebellum. Here's the draining vein, which essentially appears non arterialized at this stage of the operation. Micro scissors are used to maintain the epi-peel plane of dissection. And here is really the final stages at the surface of the malformation. Since the vein appeared completely dark, it was disconnected. So, that the very final fine feeders of the malformation are disconnected, and the nidus is extracted. Here are some of the finer feeders from the superior cerebellar artery that are being disconnected. Part of the dissection is occlusion inside too. In other words, small part of the feedings and the nidus are left behind but disconnected to minimize the future of Nidal recurrence. Here are the final connections to the lateral surface of the cerebellum. You can appreciate the importance of sharp dissection within the epi-peel space. Here's the peel surface of the brainstem, in the feeding branch from the superior cerebellar artery, that was disconnected. Here are other finer feeding vessels from the superior cerebellar artery. The root entry zone is located more inferiorly. I want to emphasize, again, this epi-peel method of AVM disconnection. Here is another feeding vessels from the surface of the brain stem. The final adhesions to the brain stem peel, are disconnected. Here's the final draining vein, that appears very dark. Obviously after this vein is coagulated, it is also transected. Here's a final view of the resection cavity. You can see the feeding vessels and potentially small amount of nidus left behind. So that the peel surface of the brain stem is not violated. You can see the root entry zone of the trigeminal nerve, some coagulation, where a small amount of AVM may have been left behind, within the prank chemo of the brain stem. And pray dominance draining vein is now dark on the surface of the brain stem Post operative, Andrew Graham demonstrated complete exclusion of the malformation without any evidence of AD shunting, and the CT scan reveal no other complicating features. This patient recovered from his surgery without any numbness on his face and made an excellent recovery, and returned to work three months, post operatively. Thank you.

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