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Parietal AVM: Managing Disturbing White matter Feeders

April 29, 2016


This video reviews resection strategies for a parietal AVM that was embolized, and also discusses management of deep white matter feeders. I will also briefly review the performance of parasagittal craniotomies. This is a 28-year-old female who presented with seizures, and on MRI evaluation was diagnosed with a paramedian parieto-occipital arteriovenous malformation. The malformation was primarily fed by the distal branches of the MCA. It ran into the superior sagittal sinus. There were also some feeding vessels from the posterior circulation. The lumbar drain was installed. There are various methods available for drainage of CSF through the lumbar cisterns, either a lumbar drain can be placed or a lumbar needle can be inserted and left in place, and a IV tubing can be connected to the needle. To avoid any displacement of the needle, I place additional padding around the hub of the needle. These blankets are taped in place and protect the needle from being inserted deeper into the spine inadvertently during the procedure. A curvilinear incision was used using neuronavigation over the right parieto-occipital area. Location of the midline is also marked Skin incision is completed. I'll review the technique for a parasagittal craniotomy. Cerebellar retractors are positioned in place. Pericranium is mobilized. I can see the location of the sagittal suture. Burr hole was placed over the superior sagittal sinus. Kerrison rongeurs are used to expand the burr hole. Hemostasis is obtained via thrombin-soaked Gelfoam. The bone flap is elevated. The initial bony cut is performed over the convexity, and the last bony cut is completed over the dural sinus. Tack-up sutures are inserted. I use thrombin-soaked Gelfoam to achieve hemostasis within the epidural space. So here's the cortical anatomy of the vessels for this malformation. You can see a relatively normal-appearing vein mixing with an arterialized vein. Here is, again, the dominant vein of this malformation, and most likely the rest of the malformation is hiding on underneath this area. Here are some of the cortical feeding vessels to the malformation. Let's go ahead and review the fluorescein angiographic findings for this malformation. You can see, again, a mixing of the contents of the normal vein with the contents of an arterialized vein. It's an interesting finding using higher magnification of such mixing of the two veins. Here are some of the feeders and then the draining vein, again, demonstrating the hemodynamic changes within this malformation, as expected. Some of the later findings within the angiogram. I continue to dissect around the malformation and control the cortical feeding vessels. I preserve as much of the normal brain as possible. The portion of the malformation close proximity of this normal vein was transected. Now I continue the parenchymal phase of the dissection. Here is a cortical or near cortical feeding vessel that has a robust wall and can be coagulated via the bipolar forceps. Obviously the primary draining vein is protected. Here is the area of the dissection around the interhemispheric fissure. The primary vein appears more collapsed. Now the deep white matter feeders can be quite challenging, especially when the malformation is over-embolized. These deep white matter feeders can become more functional when some of the more larger pedicles are embolized. I continue to circumferentially dissect the nidus of the malformation. The AVM's being mobilized. Here's the hemodynamic findings within the malformation, and the vein is still functional in this area. However, I'm going to transect the malformation since there is no venous drainage more laterally from the nidus. This disconnection allows me to mobilize the malformation based over the primary draining vein. Again, you can see these deep white matter feeders that were quite problematic in this case, despite staying outside of the area of the nidus. Small aneurysm clips were used that were partially effective in controlling the bleeding. I continue the dissection through the white matter, using the clips as necessary to control the bleeding. The vein appears darker. Therefore, most of the feeders should be excluded by now. You can see how combustive and non-competent the walls of the white matter feeders are, and they're not really very responsive to bipolar coagulation. Another clip was used in this case. I continue to further disconnect the malformation. Again, the major draining vein is much darker. Most of the malformation appears to be disconnected. Ultimately, the primary draining vein was also coagulated and disconnected. And the nidus was removed. Cutting into the nidus just to demonstrate the architecture of the malformation. Most of the nidus disappears collapsed. Final stages of the operation and achieving hemostasis. Aggressive coagulation within the resection cavity was avoided since the brain appeared very edematous and hyperemic. Under the circumstances, aggressive coagulation can often lead to more bleeding. Postoperative angiogram demonstrated complete exclusion of AV shunting, and a three-month MRI confirmed adequate removal of the mass without any ischemic or other complicating features. Thank you.

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