November 04, 2014
Let's talk about another paramedian occipital arteriovenous malformation and methods for microsurgical dissection. This is an 18 year old female who presented with an unruptured paramedian occipital malformation. The location of lesion is demonstrated. The malformation is relatively large, primarily fed from the distal branches of the PCA as expected with large draining veins, joining the superior sagittal sinus, and also straight sinus. Patient underwent a right-sided craniotomy. Prior to performance of the craniotomy partial embolization was accomplished to facilitate microsurgical dissection. Here's the exposure of lesion. A large draining vein is apparent. Here's the superior sagittal sinus transfer sinus. First, the arteriovenous malformation is carefully dissected circumferentially. All the draining veins were protected. Some of the embolization material can be quite effective in guiding the planes of dissection. Obviously the large draining vein is kept out of harms way. Small arteries around the vein are coagulated. Here you can see a relative uniform circumdissection around the nidus of the malformation. The deep white matter feeders obviously can be quite problematic. Here's one of them. Some are quite amenable to bipolar forceps, and some are very resistant as they lack robust collagenous walls. Nonetheless, I continue to persist and coagulate these vessels. Sometimes small amount of normal white matter has to be removed around the lumen of the bleeding deep white matter feeder so that a more normal appearing wall of the vessel can be found and coagulated. Here, I continue to disconnect the malformation at the apex of the lesion. It's important not to enter the nidus inadvertently. The mouth switch is quite effective for improving the efficiency of the operation. The bleeding should be controlled in stepwise fashion. One should not just pack the bleeding in one area and continue dissection in another area. The brain is relatively relaxed. The dominant draining vein still protected just behind a malformation. The AVM is gently elevated toward the vein. I sometimes irrigate the operative field with thrombin solution just to induce further hemostasis. Patients can be quite a virtue for slow arterial oozing. Gentle tamponade is also effective as long as the hemorrhage is not significant. Tamponading torrential bleeding leads to intracerebral hemorrhage, retraction of the bleeding white matters and brain swelling. AVM clips can be at times effective. Although I have been overall unimpressed by their benefits. I actually use small permanent aneurysm clips. The AVM was ultimately extracted. Now the resection cavity has to be carefully protected and inspected for any residual malformation. Here some corkscrew vessels are found. Obviously they also have to be removed. As specially in pediatric patients. Any residual AVM can become significant. Here you can see residual feeders of the nidus. We look for clean gliotic surfaces as borders. Can see a significant portion of the malformation unfortunately was left behind. I continued to use the forceps like a pair of scissors to transect the gliotic margins of the malformation and mobilized the malformation away from the operative cavity. Here I run into additional white matter bleeding it's maybe a sign that additional residual AVM is present. And I have to continue further removal of the nidus until hemostasis is reached. Initially I attempted placement of a clip. This helped some, but did not stop the bleeding completely. Such continuous bleeding is quite consistent with presence of residual malformation. And unless the malformation is completely removed, complete hemostasis cannnot be secured. Here's again, some oozing relatively slow. I'm going to inspect the cavity further. Initially gentle tamponade was used. However, later complete resection of the malformation was confirmed both with intraoperative inspection and an intraoperative angiogram. Here's another deep white matter feeder that was controlled using a small permanent aneurysm clip. I was able to achieve good hemostasis without any significant effort. Again, another important sign that the entire malformation has been resected. There's no arterialized draining veins present. The brain appears relaxed. And the postoperative angiogram also confirmed gross-total resection of the malformation and the three months MRI revealed now remarkable findings. Thank you.
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