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“Conservative” Posterior Petrosectomy

July 29, 2016

Transcript

Conservative posterior petrosectomy, an alternative to regular, more radical posterior petrosectomy, where the semicircular canals are skeletonized. In the conservative form of posterior petros approach, the semicircular canals are not skeletonized. The bone over the Trautmann triangle or pre-sigmoid area is removed just enough so that the dura anterior to the sigmoid sinus is exposed, and this form of exposure, or skull-based approach, can be utilized for smaller petroclival meningiomas along the anterior, as well as anterolateral aspect of the brainstem. Incision is relatively standard, in the form of a regular posterior petrosal approach. This is a right-sided approach. The root of zygoma is exposed. Temporalis muscle is reflected. Obviously, this is a cadaveric dissection. You can see the squamous suture, the parietomastoid suture, the lambdoid suture. Two burr-holes are placed just anterior and posterior to the sigmoid sinus, as well as superior inferior to the transfer sinus. Bone flap is elevated and a mastoidectomy is completed. The dura is mobilized so that the mastoidectomy can begin. Here, you can see the bone just anterior to the sigmoid sinus. The sigmoid sinus is marked with the arrow. So the bone just anterior to the sigmoid sinus is removed just enough, so there is a working corridor anterior to this dural sinus so that the anterolateral aspect of the brain stem can be reached. The tentorium is transected just parallel or posterior to the petrous ridge. Fourth nerve is protected along the tentorial incisura. And here you can appreciate the exposure of the fifth cranial nerve root exits shown as in the last seventh and eighth cranial nerves. The exposure is relatively good. Other cranial nerves within the posterior fossa can be also further exposed. You can see the bone over the semicircular canals are left alone. This form of pre-sigmoid craniotomy or osteotomy can be quite effective in reaching cavernous malformations along the ventral lateral aspect of the brain stem. This is a more minimalistic posterior petrosal approach. Here you can see the fourth cranial nerve that is being released from the arachnoid bands. Here's the final exposure that can be achieved through this corridor. More of the arachnoid bands can be dissected so the vasculature in this area is more visible. Again, I refer to this exposure as a conservative posterior petrosectomy, or a pre-sigmoid osteotomy. Thank you.

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