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MVD for Hemifacial Spasm: Pitfalls

October 28, 2019


This is a nice video describing the pitfalls during micro vascular decompression for hemifacial spasm. This is a 63 year-old female, who presented with three year history of left sided hemifacial spasms, high resolution MRI of the posterior Fossa revealed evidence of a vascular loop, at the root X zone of the seventh and eighth Cranial nerve complex. Left side of retromastoid Craniotomy was completed. Before we review the intraoperative findings, I would like to review the pattern of incision for this procedure. I use a curvilinear incision and myocutaneous flap in a single layer, which is reflected inferiorally so that the entire muscle scalp bulk is removed out of my way during surgery. A linear incision often bulks up the muscle and the scalp and increases the working distance toward the posterior fossa. Here you can see the landmarks the tip of the mastoid bone, the root of zygoma, the Indian, again, align connecting these landmarks together. Marks via transfer sinus, sigmoid sinus and again align perpendicular from the mastoid groove toward the transfer sinus marks the junction of the transfers sinus and sigmoid sinus. Obviously this incision is to be more inferior, as the junction of inner sinuses does not need to be exposed. Brainstem auditory evoked responses may be monitored as well as the lateral spread reflects. This nice set of illustrations demonstrate the advantages of a myocutaneous flap that's reflected inferiorly here. You can see how the bulk of the muscle is not on there, their retractor, however, for a linear incision, you can, this is a cross section view. A linear incision leads to retractor is cerebellar surface attending retractors to accumulate the bulk of the tissue under the retractor system. Again, increasing the already long working distance toward the ventral aspect of the brainstem. You can see the craniotomy, a left sided retromastoid craniotomy has been completed. The opening is relatively small, just a little bit more than a centimeter and half. The dura is incised parallel to the dural sinuses. Again, the junction of the venous sinuses is not exposed. I use a rubber dam, a piece of club under the Cottonoid to slide the Cottonoid around the cerebellum efficiently. The arachnoid bands over there, lower cranial nerves are exposed and dissected. A lumbar puncture was performed at the beginning of the procedure to decompress the posterior fossa. Forty-five CCFCSF is generally removed at the time of the lumbar puncture. Here you can see the seven and eighth cranial nerve. The lower cranial nerves. It is very important to remember that I follow the ninth cranial nerve until I find the root exit zone of the seventh cranial nerve. I actually avoid any retraction vector parallel to the seventh and eighth cranial nerves to avoid any change in the bearers. You can see that the compressive vessel is very medial and therefore ample amount of dissection around the lower cranial nerves is necessary for me to be able to see the exact side of the compression and assure that the pathology has been handled. Therefore, I'll go ahead and dissect the arachnoid bands or the ninth cranial nerve, sharply, and then continue to mobilize the cerebellum more medially, so I can see the exact side of the compression on the road exits on of the seventh cranial nerve at the level of the brainstem. Also note the use of dynamic retraction can, you can see a vessel there. There it is again, very medial at the level of the brainstem compress in the root exit zone of the seventh cranial nerve. It's very easy to inspect the more distal or cisternae aspect of the nerve and achieve an inadequate decompression of the true pathology. In other words, to compress the vessel, here you can see this side of the compression and the loop of the vessel, but I like to see the exact discoloration. This man is on the brainstem and most likely it's not the cause of the spasms. Go ahead and use dynamics retraction at the exact side of visualization. So I can see the side of the pathology here can see the exact route exit zone of the facial nerve. The discoloration. This assures me that I have found the start of the exact pathology. If a fixed retractor is placed here, it's often very difficult because the retractor creates such a wide area of force that minimizes adequate retraction. here again, you can see the eighth cranial nerve, seventh cranial nerve, the area of the discoloration where the root loop was sitting. I'm very satisfied in the discoloration of the seventh cranial nerve. One more time, the use of pinpoint dynamic retraction to identify the root exit zone of the facial nerve without placing the rest of the structures under undue tension. Now that the pathology has been found, I'll go ahead and use shredded piece of Teflon and make sure not only is there the root X its own of the facial nervous is decompress, Also the area of the brain stem next to the root X it's on of the nerve is also decompress. So I use small pieces of Teflon, mobilized the artery, and then pushed a piece of Teflon toward the brain stem. It's where the brain stem is also decompressed. Here's another piece, slightly bigger to make sure that the nerve is very well padded. Obviously oversize pieces of Teflon have to be avoided to avoid a Teflon Granuloma. can see again, use of dynamic retraction. Both instruments are being utilized to manipulate both the cerebellum and the artery while their nerves are left intact. Here, I can see that the root exit zone is very nicely decompressed. Mouth switches used to keep the image in focus and also move the microscope as necessary to bring various structures in view. No other compressive vessel is found. Another small piece was placed to make sure that the loop is not contacting the cisternae segment of the nerve either. I use irrigation and pull of it to make sure that the Teflon is not going to move after surgery. Having soak gel foam is also used to bath the vessels and to relieve any vasospasm. And as you can see in the final product, the openings relatively small myocutaneous flap was mobilized inferiorally to decrease the work in distance towards the nerve and all of these details, hopefully can facilitate the work of the surgeon and improve the outcome of the surgery. Thank you.

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