June 16, 2015
Petrosal AVMs are rather non-eloquent and their resection is relatively safe. This is the case of a 74 year old male with a known petrosal malformation who presented with a large cerebellar intracranial hemorrhage. These are the imaging studies prior to his presentation, with the hemorrhage on the axial MRI images. You can see the location of the nidus facing the petrosal bone. On the enhanced images again, you can see the location of the malformation on the lateral aspect of the cerebellum. A lateral vertebral injection angiogram demonstrates the nidus of the malformation, the feeding vessels primarily from their superior cerebellar artery, as well as the posterior inferior cerebellar artery. The main draining vein joins the tentorium as part of a cerebellar hemispheric vein. An AP injection of the vertebral artery also demonstrates the nidus of the malformation, and the draining vein joining the transfer sinus. At the time of the presentation with a hemorrhage the patient was neurologically compromised, you can see the size of the hemorrhage. Patient was suffering from hydrocephalus, he underwent placement of an external ventricular drain, and subsequently an emergent lateral suboccipital, as well as a retro mastoid craniotomy. Here's the transfer sinus, sigmoid sinus. We're on the right side. Patient in the latter position. The wedge of the cerebellum affected by the hemorrhage was removed. This cap of cerebellum is essentially non-functional since it is been completely disconnected by the hemorrhage. Usually patrosal AVMS are approached via a retro mastoid craniotomy. Going around the cerebellum to reach the cerebellopontine angle, and tackle the malformation tangentially. This is an unusual case because the hemorrhage has already created a corridor by disconnecting the superficial cap of the cerebellum. I continue to work around the malformation, disconnect the white matter feeding vessels. Always the hematoma is evacuated as soon as possible to provide cerebellar relaxation and minimize the amount of retraction on the surrounding normal cerebellum. Right now I'm working along the inferior margin of the malformation, as well as laterally you can see the dura over the petrous bone. Essentially we went through the affected cerebellum to reach the petrosal surface of the malformation, all the feeding vessels from the PICA are disconnected. Now, that the more inferior and latter aspect of the malformation is disconnected, I continue to divert attention to the medial part of the malformation. Often the medial part is the most difficult because that's where the white matter feeders originate from. Here you can see the nidus of the malformation continuing the white matter desection more medially. I stay beyond the boundaries of the nidus to make sure the white matter feeders are controllable. I left this piece of the video relatively unedited to show some of the strategies for management of the bleeding from the nidus. Aggressive suctioning over the nidus obviously should be avoided. Some of the white matter feeders close to the malformation as you can see can be quite problematic. You see that one of these white matter feeders close to the nidus started to cause bleeding, and the issue here is that as you try to control this white matter feeder you end up getting closer and closer to the nidus leading to more hemorrhage, and obviously any acute change of the hemodynamics of the malformation without disconnection of the all feeders can be quite problematic. Here I persisted and attempted to control the bleeding via coagulation because I felt most of the feeders were disconnected besides the one coming over the superior aspect of the cerebellum. If most of the malformation is not disconnected, I usually use a piece of cotton soaked in thrombin with gentle tamponade, the bleeding from the malformation can stop readily. So, as that bleeding was controlled I had diverted my attention along the dura of the petrous bone. Here's the petro tentorial junction again petrous bone tentorium working at the level of the junction to disconnect some of the SCA feeding vessels coming over the lateral slope of the cerebellum. Now, they being disconnected, malformation appears relaxed. Now, I continue to complete the more superomedial part of the AVM disconnection. This is the part where most of the SCA feeding vessels travel over the medial slope of the cerebellum to reach the nidus. Here are some of the final attachments from the interior cerebellum. Obviously the draining vein is located superiorly and is left intact during the entire procedure. We're getting to the very final feeding vessels from the SCA. Let's go ahead and disconnect those, so that next the vein can be disconnected and the malformation delivered. Again, here working through the subpial space to find a feeding vessels. One is here, obviously they shouldn't be evolved inadvertently. So, now the malformation is disconnected, the draining vein is coagulated and cut, the nidus is removed. Hemostasis is secured by coagulating the edges of the peel surfaces where the feeding vessels enter the nidus. I also use thrombin solution to irrigate the operative field. This maneuver further promotes hemostasis, as you can see here without the use of suction. Postoperative CT scan demonstrated complete removal of the hematoma, no complicating features, and the angiogram also confirmed complete disconnection of the malformation without any AV shunting. Thank you.
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