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Anterior Pontine AVM and Meckel’s Cave dAVF

April 29, 2016


This is an anterior pontine arteriovenous malformation associated with a Meckel's cave Dural arteriovenous fistula. The video describes the technique of in-Situ occlusion method for obliteration of the malformation and exclusion of the fistula. This is a 48 year old male who presented with a thunderclap headache. CSF evaluation by a lumbar puncture demonstrated evidence of xanthochromia. The malformation is evident along the anterolateral aspect of the brainstem on the right side. The malformation appears to encase the fifth cranial nerve and extends just medial to the fifth cranial nerve and therefore, it's an anterior pontine malformation. Let's go ahead and review the angio-architecture of the malformation and the fistula. The fistula as expected, originates from the tentorial branches of the internal carotid artery, the malformation itself, again, as expected, primarily fed from the superior cerebellar artery and anterior inferior cerebellar artery branches. The superior petrosal sinus does not appear to be involved with a drainage pattern of this malformation. The venous drainage is primarily medial through an anterior pontine vein, and another slightly more lateral brainstem vein, most likely superiorly pointed. This is another higher magnification view of the malformation, showing the feeding vessels from the superior cerebellar artery and anterior inferior cerebellar artery branches. Most of the anterior pontine malformations are not primarily resectable without injuring the brainstem and therefore, in-Situ occlusion of the feeding vessels are most safe in terms of excluding the malformation. The patient underwent a right-sided retro mastoid craniotomy, you can see the curvilinear incision, the location of the transfer sinus and the location of the mastoid groove. Extent of bony removal involved unroofing of the sigmoid sinus, so a more lateral trajectory can be obtained around the sinus and the sinus can be mobilized during Dural opening layer retention sutures. The Dural was opened in a curvilinear fashion. This is a standard technique that I use for extended posterior fossa approaches. Here's the extent of Dural incision. tentorium and their junction. Here's the junction of the two, arachnoid bands are widely opened. We used ICG and flow 800 to evaluate the degree of flow within the neurovascular structures in this area. You can see the seventh and eighth cranial nerves readily apparent, here is the fifth cranial nerve at the depth of our exposure. All the arachnid bands are widely open to avoid any tension on the seventh and eighth cranial nerves. Brainstem auditory evoked responses were also monitored during this procedure. Here's the fifth cranial nerve, you can see it's intimately associated with a malformation, the corkscrew vessels are evident. This is most likely a vessel involved with the arteriovenous fistula. Here's the fourth cranial nerve. More of the feeding vessels from the super cerebellar artery are being exposed, wide opening of the arachnoid bands is necessary, here is the malformation, hogging the root entry zone of the fifth cranial nerve. Here's the vessel most likely involved with the fistula. I did not suspect that this is a draining vein. Some slight bleeding from the surface of the malformation was controlled using gentle electrocautery, again the seventh and eighth cranial nerve, the fifth cranial nerve one of the fistulous connections for the arteriovenous fistula. The drainage pattern for the veins are most likely along the anterior pontine area away from the operative corridor, based on defining on preoperative angiogram. Here's further dissection along this cisternal segment of the trigeminal nerve. To identify the feeding vessels, obviously, complete removal of the malformation is not safe. And the safest method is, just in-Situ occlusion of the feeding vessels to disconnect the malformation circumferentially but leaving the nidus behind. Looking just interior to the fifth cranial nerve you can see some of the draining veins most likely located along the anterior pontine area. Let's go ahead and do an interpretive ICG angiogram to better define the angio-architecture of this malformation and see the character of this vessel here. The flow 800 Color Map will demonstrate that this oddity that I suspected is most likely arterial in nature as it's red and it's very early on during the angiogram. Also, the feeding vessels from the anterior inferior cerebellar artery are quite evident. Here's the location of the tentorium for your orientation. I felt encouraged that I'm safe in terms of taking this vessel. Exclusion of this vessel would allow me to go around the malformation more effectively and see the feeding vessels from the superior cerebellar artery. Here again is some of the nidus of the malformation potentially an arterialized vein more anteriorly. I placed a temporary clip on the suspicious vessel, and the AVM appears quite relaxed, therefore this vessel was excluded and subsequently disconnected. Now it's time for me to find the superior cerebellar artery feeding vessels that are being coagulated here as you can see, one by one, I'm going to disconnect these corkscrew vessels feeding the portion of the malformation just medial. To the axilla of the fifth cranial nerve here, the branches of the superior cerebellar artery that should be carefully protected, they're not traveling toward the malformation, only the small corkscrew vessels projecting toward the nidus inferiorly are being coagulated and cut. Small bleeding from one of the feeding vessels is timely controlled. Then you can see the characteristic corkscrew vessel going to the malformation along the entry ponds that is being coagulated and cut. Most of the feeding vessels appear excluded, Now I come inferior to the root entry zone of the nerve and disconnect these feeding vessels from the anterior inferior cerebellar artery. There has to be more dominant feeding vessels, more medial to the nerve, especially one or two from the trunk of the basilar artery, most likely this is the one from the trunk of the basilar artery that has been carefully disconnected and cut. Again any corkscrew vessel just medial to the nerve projecting superiorly toward the nidus has to be coagulated and cut. Here appears to be one more just at the very depth of our dissection cavity. Now I come more superiorly and just above the nerve, disconnect some of the feeding vessels along the entry ponds going to the nidus of the malformation which is essentially encompassing the nerve and the brainstem around the axilla of the nerve. Here are the vessels of the superior cerebellar artery that are protected. Here's the fourth cranial nerve The vessels obviously have to be carefully preserved to avoid cerebellar and brainstem ischemia. In some of the small corkscrew vessels at the root entry zone of the nerve are also very carefully coagulated without any surrounding neural injury. Some of the very deep vessels along the inferior aspect of the nerve are being re coagulated, the tiny ones going to the malformation are being disconnected. You can see the seventh and eighth cranial nerve complex that is being carefully mobilized inferiorly using dynamic retraction, here's the sixth cranial nerve entering the Dorello's canal. Appears that all the feeding vessels just below the nerve are disconnected. I attempt to transect them when possible to minimize the risk of recanalization. And is the nerve, here is another ICG and flow 800 evaluation for the vessels that are remaining just medial to the axilla of the nerve. And here you can see that the remaining vessels just entering the tentorium are most likely fistulous and are related to the Dural arteriovenous fistula. So, these vessels are disconnected, you can see they have a very thick wall, they are arterialized as expected, they're part of the Dural arteriovenous fistula fit by the tentorial branches of the internal carotid artery. Disconnection of this fistulous connection allows further mobilization of the arterialized vein related to the fistula in adequate visualization medial to the axillary of the nerve to assure that all the small feeding vessels to the malformation are disconnected. Here is part of the fistula that is most likely involving the Meckel's cave following the trigeminal nerve into the Meckel's cave. I attempted to coagulate this part of the fistula as well. Here you can see an vessel turning inferiorly, most likely not related to the malformation. Obviously this artery has to be protected. You can see how important it is for every vessel to be carefully inspected before it is sacrificed, so brainstem ischemia does not occur. Continue to work around the fifth cranial nerve to assure that all the small feeding vessels are identified. Here you can see maybe a small feeding vessels that was overlooked during my prior inspection, and that was taken care of as well. You can see this superior cerebellar artery branches that are not involved at this segment with a malformation. I continue to dissect around the arterialized fistula that was disconnected more anteriorly to make sure there are not small feeding arteries to the malformation that specifically involves the cisternal segment of the trigeminal nerve. Here's the nerve, looking at the depth of the brainstem, I do not see any clear feeding vessels to the nidus, here is this sixth cranial nerve entering its foramen. Here's part of the Meckel's cave fistula that is just anterior to the cisternal segment of the trigeminal nerve. Some of the feeding vessels to the fistula are apparent. I coagulated some of these feeding vessels to disconnect any remaining Dural arteriovenous fistula around the Meckel's cave. This appears to be just a vein. Just at the area of the Meckel's cave, I attempted to coagulate as many of these vessels as possible. Obviously visualization along the anterior aspect of the nerve can be quite limiting. Also attempted to avoid any injury to the nerve, here are some of the small feeding vessels to the Meckel's curve fistula, These are being also coagulating and disconnected. You can see the work angle is quite oblique and difficult. After I disconnected those feeding vessels, all the veins appeared dark and collapse. You can see some of the feeding vessels along the posterior aspect of the nerve that were also coagulated. The final interoperative ICG and flow 800 Color Map demonstrates no evidence of arterialization of any of the veins around the nerve. I'm quite satisfied with the results of disconnection. You can see perforator off of the basilar artery that is , this vessel was left intact. And the post operative angiogram demonstrated complete obliteration of the tentorial Dural arteriovenous fistula, also the distal along the Meckel's cave. In addition, the arteriovenous malformation is completely obliterated without any evidence of arteriovenous shunting. This patient had some worsening of his facial numbness, but otherwise remained completely neurological intact and made an excellent recovery and subsequently returned to work. Thank you.

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