Repeat MVD for Hemifacial Spasm: Pitfalls
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Repeat microvascular decompression for Hemifacial Spasm can be quite tricky and technically hazardous. If certain principles are not respected. This is a 60-year old male who underwent an MVD operation about 10 years ago by a very reputable neurosurgeon. But unfortunately never benefited from any resolution of his spasms. Even immediately after surgery. Repeat MRI evaluation at the time of his presentation. For my evaluation, demonstrated a dolichoectatic artery compressing the root exit zone of the facial nerve. However, there was a very sizable piece of Teflon mobilizing this vessel. I suspected that an arterial branch was initially overlooked at the time of the first index operation. A re-operation was offered. Brainstem auditory evoked responses, and the lateral spread reflects were monitored during the surgery. You can see that left sided retromastoid craniotomy through the previous linear incision. The lateral aspect of his cerebellum is quite adherent to the petrous dura. CSF is drained along the cisterna magna and the lateral surface of the cerebellum is disconnected from the petrous dura. Here's further CSF drainage. Now, they scalding surface of the tentorium is disconnected. I strung my dissection further inferiorly along the turn of the petrous dura toward the floor of the poster fossa. Here are the lower cranial nerves. I identified the ninth cranial nerve and follow its route to reach the route exit zone. Of the seventh cranial nerve. Arachnoid bands are shortly dissected. Here's the tentorium petrous bone. Obviously our dissection will be directed more inferiorally. Here's the previous dissection cavity and a piece of Teflon that was used to mobilize the large dolichoectatic vessel. Here's the ninth cranial nerve. I suspect this seven and eighth complex to be mobilized superiorly immediately by dead piece of Teflon. Here's most likely a piece of Teflon touching the middle cerebellar peduncle. The nerve is most likely, still deeper. And more medial. Here's the fifth cranial nerve above the piece of Teflon. Some of the adherent or two branches are mobilized. Here's probably the root exit zone of the seventh cranial nerve. Can the middle cerebellar peduncle. One of the arterial branches that could be potentially the offending vessel just above the ninth cranial nerve. It can fall on the route of the ninth cranial nerve immediately. Towards the brain stem to find it. Exit zone of the seventh cranial nerve. Some of the branches are mobilized to expand my view toward the medial aspect of the Teflon. You can see use of arachnoid knives to dissect the adherent vessels. The presence of the intense scar adds a different level of complexity to this operation. Now I'm able to work with it. To flown a little bit better under higher magnification. You can see the ninth cranial nerve. You can see the old Teflon. You can see the seven and eighth cranial nerve complex at the level of the brain stem. You can see an offending vessel that was most likely overlooked during the initial index operation. This can be... a large labyrinthine artery traveling between the seventh and eighth cranial nerves. The arachnoid bands are left over the brain stem and the cranial nerves to minimize their injury. Here's a vascular loop contacting the... exit zone of cranial nerve seven around the brainstem. Continue di-sharp dissection to better characterize the route of the vessel that I'm potentially considering an offending vessel. At the shoulder of the nerve no offending vessel was found. I redirect my attention at the axilla of the seventh nerve. This vessel is very adherent to the Teflon and cannot be safely dissected. Therefore I follow the route of the offending vessel. You can see this coming in contact with the exit zone of the seventh cranial nerve. The bearers remain stable. Some of the perforating vessels apparent. The eighth cranial nerve. Here, further dissection of the seven and eighth complex. Mobilization of the offending vessel. However, keeping the vessel away from this seventh cranial nerve can be quite challenging. I continued sharp microdissection. And attempted a number of strategies to keep the vessel away from the brain stem. Since the vessel was very adherent to the old Teflon. I attempted removing part of the Teflon. To create more space. As I could not disconnect the Teflon from the vessel. Unfortunately, ultrasonic aspirator was not effective on removing and evacuating or de-bulking the Teflon. A scissors appear to be more effective. Some reduction in the volume of the Teflon patch was accomplished. Next. I attempted to place a suture within the Teflon. Which was very adherent to the offending vessel. So, that the suture can be sewn into the petrous dura to keep the artery away from the route exit zone of the facial nerve. You can see the Teflon is really embedded in all the surrounding vessels. It's removed and well It's not safe. Here you can see the vector of retraction necessary for mobilizing the offending vessel. I first attempted placing a clip and then suturing the clip to the petrous dura. I used a number of different clip configurations to pull on the Teflon, using a suture. Essentially using the clip as a handle to pull on the Teflon. Here's the suture going directly across the Teflon patch. As the clips did not appear to work well. Here's the suture placed through the petrous dura. Acting as a slang. However, the suture broke through the Teflon and was not a definitive solution. Here you can see the vessel is mobilize. But unfortunately the suture is not maintaining its stability. My last option was using shredded piece of Teflon around the perforating vessels. To mobilize the vessel away from the facial nerve. You can see additional space has been created. I'm gonna go ahead and fill in these spaces with small patches of shedded Teflon. A large piece would place this perforating vessel at risk of avulsion injury. Here, you can see the ninth nerve. The root exits on of the seventh cranial nerve. The offending vessel. Here's the first small pieces of Teflon. Just below the perforating vessel. The next one is placed above the perforating vessel. The two patches straddle the perforating vessel to the brainstem. You can see the second one is more flattened. So, it can be inserted along the length of the offending vessel. Obviously parallel to the access of the vessel. I felt adequate mobilization has been achieved in the vessel is no longer in contact with the facial nerve exit zone. Lateral spread reflex disappeared. After the vessel was permanently mobilized. I can see the facial nerve exits on is discolored. Assuring me that the pathology has been adequately addressed. Here's the magnified view of the operative field. The vector of retraction is not parallel to the seventh and eighth cranial nerves. Post operative CT demonstrated adequate result without any complicating features. Thank you.
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