I opened the dural somewhat differently than most people for a retromastoid craniotomy. This is again a left-sided retromastoid craniotomy. You can appreciate the transverse sinus turning into this sigmoid sinus at the tip of my arrow. This is relatively a sizeable craniotomy for a typical microvascular decompression surgery. However, a larger craniotomy is usually used for resection of tumors. In this case, I opened the dural parallel to the dural venous sinuses. In other words, parallel to the sigmoid and transverse sinus in the fashion you see in this video. This leaves most of the dural over the cerebellum. Number one, protects the cerebellum, and number two, prevents shrinkage and drawing of the piece of the dural, most of the dural that is already away from the intense light of the microscope. I often see that operators open the dural and reflect the dural based over the sigmoid sinus. However, that leaves most of the dural along the edges of the bone very much exposed to the light of the microscope, and that can lead to shrinkage of the dural and difficulty with adequate dural closure. I then place three tack-up stitches to be able to mobilize the sigmoid sinus laterally, and therefore advance my operative corridor around the cerebellar hemisphere. The first stitch is around the sigmoid sinus. The second stitch is along the transverse sigmoid junction. And the last stitch would be somewhat along the more lateral aspect of the transverse sinus. You can see again, most of the dural is left on the cerebellum and is protected from the intense light of the microscope. This allows a nice trajectory around the cerebellum to be able to access the cerebellopontine angles cisterns, and also somewhat elevates and mobilizes the sigmoid sinus away. I use a piece of rubber dam, which is usually a piece of cloth that is cut to the size of a carotenoid, and then slide the cottonoid over the rubber dam to go around the cerebellum. This maneuver protects the cerebellum from friction and the coarse or rough surface of the cottonoid.
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