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Medial Occipital AVM

July 29, 2016

Transcript

Here is another nice example of a large left medial occipital lobe. This is a 42 year old male who presented with seizures. MRI evaluation revealed this large AVM effecting the left medial occipital lobe with a large draining vein, joining the vein of Galen. An initial preoperative angiogram demonstrated the size and aggressive AV shunting within the malformation. Multiple PCA or posterior cerebral artery feeding vessels, were leading to the malformation. More specifically, there was a very dominant one leading to the malformation. The drainage pattern as expected joins the Galenic system. Due to inaccessibility of the feeding vessels from the PCA during the initial stages of dissection, the dominant feeding vessels from the PCA to the malformation was embolized. However, there were numerous other feeding vessels from the PCA leading to aggressive amount of AV shunting. Patient when resection using a paramedian leading her incision, here is the midline or the sagittal suture, the affected occipital lobe or the left one was placed in the dependent position so that gravity can facilitate mobilization of the occipital lobe away from the focis. In addition, a lumbar drain was used for this procedure. Here's the exposure, the mid-line dural was opened in a curvilinear fashion based or the superior sagittal sinus. You can see that drainage of CSF through the lumbar drain and gravity retraction mobilizes the occipital lobe spontaneously away from the focis and the tentorium located here. The initial steps of dissection involved opening of the arachnoid membranes over the clinanik system, identifying the draining veins and feeding arteries. Here's the edge of the posterior aspect of the foci. Joining the tentorium, this location, here's that embolized dominant PCA branch, the embolization material can function as neuro navigation so that preoperative angiogram findings can be transposed over intraoperative findings. Here's another PCA branch leading to the malformation located here. This PCA branch is being isolated. I initially wasn't sure if this is a vein or an artery, very arterialized veins can look very similar to arteries. Here's the nitis of the malformation. Further dissection along the posterior foci was necessary to expose the tentorium and better define the angio architecture and the borders of the malformation. Again, here is another look of the malformation. Further dissection was completed to make sure arterialized veins are differentiated from feeding arteries. Before I transect anything more anteriorly, I decided to circumferentially disconnect the malformation. Here's the nitis heavily populated by large veins that are wrapping around the nitis. All these veins have to be carefully protected since they're in the main drainage system of the malformation. You can see the malformation is quite tense, not easily mobilizable away from the brain. Here's further dissection along the posterior foci leading to tentorium. I wanted to assure myself there are no other feeding vessels coming around the edge of the tentorium to the malformation more posteriorly, all arachnoid bands are being dissected. Small dural feeding vessels should be coagulated and cut, again, you can see gravity retraction being quite effective in mobilizing the brain without the use of fixed retractors. Here you can see the portion of the poster of foci, some of the trans dural feeding vessels to the malformation. I'll go ahead and move my dissection more posteriorly eventually. So that the foci tentorial junction is quite evident. Here, now I can see more inferior edge of the malformation, again, I continue to move posteriorly. You can see the foci tentorial junction just about here. Now I am disconnecting the malformation along its more superior and posterior borders. Here you can see the very tense malformation with a large vein wrapping around the malformation. Some point during the surgery, one may feel that this malformation has both fistulas and AVM features. Now moving along, the more lateral port of the malformation, using sharp dissection, enter into the nitis and these veins should be carefully avoided. Now this appears to be more of a draining vein, actually leading to the Galenic system. Initially it's a very arterialized feature led me to believe that it can be an artery. Here's another corkscrew vessel leading to the malformation along the posterior aspect of the foci. This one was easily control upon its rupture, again, embolization material from that dominant feeding vessel of the PCA. All arachnoid bands are generously opened. So the surgeon can understand the surrounding cerebrovascular anatomy effectively. Here's potentially another feeding vessel to the malformation, again the embolization material. I continued to now disconnect the malformation along its inferior aspect, this cork school vessel that was leading to the malformation from the distal PC, it branches was also coagulated and sacrificed. Here is another vessel. I continue to follow that vessel. It appears that it ends up into that distal PCA dominant branch, here is removal of the clot, but as you can see, removal of the clot within the lumen led to bleeding of the vessel that was previously embolized. However, the vessel was coagulated in a timely fashion. So this dominant branch of the PCA is now completely disconnected. Here is another branch of the PCA leading to the malformation. This branch is also quite coagulated and cut. As you can see, one has to remain patient, carefully expose the cerebrovascular anatomy and make sure all the feeding vessels are reliably identified, transected, and cut. Here's the more the de magnified view of the operative corridor with the AVM located here. Now I'm going to divert my attention more posteriorly, see if there is any other feeding vessels to the malformation. Again dissecting more posteriorly along the area, very close to the foci tentorial junction. You can see these large vessel, again, its identity has to be confirmed first, here's the draining vein. I suspect this is arterial. This is draining vein. Let's go ahead and do an ICG to confirm our suspicion. Before I do that, the temporary occlusion of this vessel did not lead to any AVM swelling. Again, increasing my suspicion that this is an arterial rather than venous structure. I see, as you confirm the character of that vessel as arterial and therefore that vessel was also sacrificed. I continued to go around the malformation, again, the dominant draining vein is protected at all costs. It's temporal occlusion revealed minimal amount of swelling of the malformation. So most of the malformation is now disconnected and can be mobilized anteriorly. However, this nitis is quite big and it's challenging to remove it without aggressive retraction of the occipital lobe. So I'll go ahead and do my best to shrink it a little bit using bipolar coagulation. Dynamic retraction was used to reach the more lateral pole of the malformation. And here's another ICG showing minimal flow within the vein at the tip of my arrow. Therefore, the malformation is just about ready to be extracted. The vein was clipped and cut. The final steps of the operation involve removal of this large mass. In this case, a piecemeal removal of the malformation was necessary to avoid cortical injury. Obviously this maneuvers should be avoided at all cost on unless all the feeding vessels are this disconnected. So the larger portion of the malformation was removed. The small residual portion of the malformation will be removed in the second stage. So here's the second stage. Here's the occipital lobe that was entered. And the occipital horn of the lateral ventricle, here is its wall. Obviously this malformation reached the ventricle at this location. The malformation was disconnected sharply from the more medial wall of the ventricle. This illustrates an exposure toward the occipital horn of the lateral ventricle using the inter mesospheric occipital approach. Here's the last piece of the avion that is being delivered. This last piece was also excised. Hemostasis was secured, postoperative angiogram revealed complete disconnection of the malformation and the CT scan did not reveal any complicating features, although this patient's vision worsened slightly after surgery, this worsening significantly improved at the three months follow up, thank you.

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