MVD for Hemifacial Spasm: Principles
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This video reviews the nuance of technique for microvascular decompression for hemifacial spasm. This is a 62-year old male with disabling left-sided hemifacial spasms. MRI evaluation revealed a dolichoectatic vertebral artery with an associate branch of the PICA compressing the root exit zone of the facial nerve. Patient underwent small left-sided craniectomy. You can see the location of the mastoid groove. The craniectomy is relatively small and it's placed just at the highest point of the mastoid groove. The transfer sinus is not exposed. Just the most posterior limits of the sigmoid sinus is unroofed. You can see that the craniectomy is just a little bit larger than one centimeter. It's in fact about 12 or 13 millimeters. A curvilinear incision was used and a myocutaneous flap was reflected inferiorally. As the petrous dura curves around to become the floor of the posterior fossa, I advanced the cottonoid patty and find the lower cranial nerves through the arachnoid bands. These bands are opened and additional CSF is released. Next I go ahead and use the knife cranial nerve as a roadmap to find the root exit zone of the facial nerve. Here you can see my operative trajectory was directed more inferiorally, the cerebellum was untethered from the ninth cranial nerve, numerous vessels are present within the cisternal segment of the facial nerve, but the offensive vessel most likely is located at the root exit zone of the nerve at the level of the brainstem. Here's the eighth cranial nerve, seventh cranial nerve, a vascular loop is apparent, dynamic retraction is used. The vessel is mobilized. You can see a large vascular loop. Here's the diathetic vertebral artery that was present on the MRI. Here's exactly the route takes its own of the facial nerve. The loop is mobilized. You can see the clear indentation caused by the vascular loop and the discoloration at the level of the root exit zone of the nerve near the brainstem. Finding this indentation and discoloration is quite important to provide the confidence that the surgeon has found a pathology that is responsible for the patient's spasms. Again, the facial nerve is located there. You can see the discoloration, the indentation in the brain stem, very nice demonstration of a Pethel anatomy is evident. Again, the eighth cranial nerve, seventh cranial nerve, labyrinthine artery often travels between these two. Pieces of shredded Teflon is used to mobilize the offensive compressive vessel away from the root exit zone of the nerve. You can see the use of dynamic retraction and bimanual dissection to place the shredded Teflon pledgets without using fixed retractors. And other pieces inserted to make sure that the artery is thoroughly away from the brain stem. I'm pretty satisfied at this point. Another small piece can further assure no contact in a delayed fashion between the artery and the nerve. And here's the vascular loop. You can see its entire segment is decompressed away from the brain stem and not just a part of it. This thorough decompression is quite paramount for addressing the cause of neurovascular conflict. Irrigation is used, making sure the implants are not moving. They appear to remain in their initial place. Here's another view of our decompression and placement of the Teflon pledgets. This is a demagnified view of our operative corridor. Cerebellum appears very healthy via the use of dynamic retraction. You can see again the size of the craniectomy relative to my thumb. All the air cells are thoroughly waxed to avoid formation of any postoperative CSF fistulas. And the dura is approximated primarily in a watertight fashion. Thank you.
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