Basal Occipital AVMs
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Let's review tenets for resection of basal occipital arteriovenous malformations. This is a 52 year-old female who presented with a three centimeter unruptured left basal occipital arteriovenous malformation. You can see the location of the mass in relation to the tentorium, as was the lateral extent of the lesion. A cerebral arteriogram demonstrated the angioarchitecture of this malformation, primarily fed by the distal branches of the posterior cerebral artery, with a large dominant draining vein reaching within the interhemispheric space to join the superior sagittal sinus. The nidus is relatively compact. This patient was placed in a lateral position using a lumbar drain. The left side was placed down so gravity retraction can be used to open the interhemispheric space for reaching the inferior and the medial aspect of the occipital lobe. The craniotomy exposed the superior sagittal sinus and the torcula. Here's the area of the superior sagittal sinus. Here's the left side. A small portion of the bone also on the right side was removed. So retention sutures can be removed to mobilize the sinus contralaterally and open the interhemispheric corridor. The dura opening is standard in a curvilinear fashion based over the superior sagittal sinus. Here's the draining vein that is localized early on and protected. Two retention sutures are placed within the posterior aspect of the falx to mobilize the superior sagittal sinus. You can see another draining vein there. A small corticotomy was necessary to expose the nidus, which is again, relatively compact. There was a small cyst associated with this malformation. The nidus of the malformation is readily visible. Standard techniques were used to circumferentially dissect the malformation while preserving the draining pedicle more superiorly. Here you can see some of the gliotic margins. The avium is being released along its circumference. The feeders are being carefully disconnected. Here's a more medial aspect of the avium that is being disconnected. The nidus was removed. However, some bleeding was encountered along the superior portion of our resection cavity. Small residual was suspected, and this area was carefully inspected and bleeding was controlled. You can see the draining vein is quite dark now. I'm very satisfied with the results of the resection, specially with the degree of darkness of the draining vein. Post-operative angiogram demonstrated complete resection of the malformation and the MRI did not reveal any complicating features. The patient did not suffer from any visual field deficits. The important learning points are, adequate positioning to mobilize the hemisphere using gravity retraction, to work both medial to the falx and involve the tentorium. Obviously localize the draining vent early to keep it out of harm's way, and continuous circumferential dissection and ensuring that the draining vein has turned dark blue. I routinely perform intraoperative angiography to confirm gross total resection of the malformation. Thank you.
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