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Craniotomy and Decompression for Glossopharyngeal Neuralgia

January 17, 2015

Transcript

There is much controversy, about what is the best technique, for MVD, or neurotomy, for glossopharyngeal. I have used Cranial Nerve 9 transection, and microvascular decompression surgery for cranial nerve 10, with great success, in managing this pain syndrome. This video reviews the technical nuances for this procedure. This is a 69 year old patient of mine who presented with, right-sided glossopharyngeal neuralgia, as well as syncopal episodes. On this high resolution, T2 axial MRI. There is evidence of vascular loop at a tip of my arrow, as well as the black arrow. At the axilla of the lower cranial nerves entering the jugular foramen. You can see there's also another vast conflict on the left, but unequivocally this patient had evidence of the pain on the right side and syncopal episodes. He subsequently underwent a right-sided retromastoid craniotomy. The patient was positioned in a lateral position, and a curvilinear incision was used. I'm going to review the plating of the incision as you can see, the initial horizontal line is drawn from inion, to the poster rooter zygoma. The second line is a vertical line over, the groove of the mastoid. The junction of these two lines defines the junction of transfers and sigmoid sinuses. Since most of the work is done along the lower cranial nerves, the summit of our incision does not need to expose the junction of these dural sinuses. Therefore we plan a curvilinear incision whose summit, is about one centimeter below the junction of dural sinuses. The shoulders moved out of the way, to create extra space. The myocutaneous flap is reflected inferiorly. Again this is a right sided rich mastered approach, you can see the mastoid, and the mastoid groove here, and we essentially start our burr hole, and expand it, to create a craniectomy, starting at the tip of the mastoid groove. Following completion of an expanded craniectomy, which is typically just slightly larger than a quarter coin a curvilinear neural opening, is completed parallel to the sigmoid sinus, as well as the floor of the posterior fossa. You can see the edge of the sigmoid sinus was exposed, during our initial craniectomy. One of the crucial landmarks in this procedure is, where to start the section around the arachnoid membranes, of the CPA angle. As you can see, this is the petrous spondura, as it's turning around to, become the floor of the posterior fossa. This curve defines the location where we start, our dissection along the lower cranial nerves. Gently, the cerebellum is lifted, super medially the arachnoid membranes are exposed, they're sharply cut, and again, micro scissors are used to open the arachnoid membranes widely over the lower cranial nerves and avoid any undue traction on the nerves. Fixed retractors are avoided. You can appreciate the 9th cranial nerve, that can be separated from the 10th cranial nerve rootlets. Here's the vascular conflict. As you can see, right, pushing the 9th nerve toward us, this is very typical of the finding during this approach. Here's choroid plexus. We'll go ahead and create more space to be able to manipulate the vessel. We first transect the 9th cranial nerve. We have had almost no complication in doing so. After nerve is transected, very close to the brain stem, We'll go ahead and dive our attention, to mobilize the artery away from the axilla of the 10th cranial nerve. This is a very difficult region to expose and I mean the axilla of the 10th cranial nerve, and the surgeon has to work very closely in that area, while avoiding significant traction on the lower cranial nerves. This is another anatomy of the 7th and 8th cranial nerve, just for understanding of anatomy, not that the section around this region is necessary, and you can see in this patient how, the 7th cranial nerve and 8th cranial nerve were very much separated from each other. I just made sure that there are no arachnoid membranes necessarily placing traction, on these nerves during our manipulation. After we have assured that these nerves are safe, we divert our attention back to the lower cranial nerves. I start using small pieces of shredded Teflon, to mobilize this anterior loop, away from the axilla of the 10th cranial nerve. Again, this is area that cannot be directly visualize, otherwise the traction on the vagus nerve can be significant and can lead to a post operative, a swallowing difficulty. So I'll go ahead and start using, small pieces shredded Teflon, and just insert them between the brain stem, the nerve, and the vascular loop. Often a number of shredded pieces of Teflon are necessary, the perforators as you can see are carefully protected, and this step-by-step, gradual mobilization of the artery using small pieces of shredded Teflon seemed to be the safest way in my hands, to mobilize the artery completely, away from the fissure, the medial fissure between the 10th cranial nerve and the brain stem. Here's another piece that was inserted. We'll go ahead and see that the artery has been relatively well mobilized away. However, additional pieces are placed to completely exclude any contact between, the root takes its own of the 10th cranial nerve and artery, as well as any contact between the brainstem, and the vascular loop. As more pieces of shredded Teflon are placed, occasionally some kink in the vessel can be present. And we assure that this kink is not exclusive. And an intraoperative micro-doppler ultrasonography is used to assure that the flow is intact, which is in this case, it was. And again, it's not just adequate to decompress the root entry zone of the nerve. The brainstem has to be also thoroughly, decompressed all the way above, as you can see of the nerve and below the nerve, to assure that all the areas of contact, between the vascular loop are excluded. And here is where you demagnify the viewer of our operative corridor and the final results. The dura is approximated in a watertight fashion and a cranioplasty performed, and the rest of the incision closed, in the anatomical layers, thank you.

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