Posterior Petrosectomy: Cadaver Dissection
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Let's use this cadaveric dissection video to describe the nuances of technique for a posterior petrosectomy. You can see the curvilinear incision based over the ear. You can see this is the exposure on the right side. Following completion of the incision, the scalp flap is reflected inferiorly, and the suboccipital, as well as temporalis muscle are also mobilized inferiorly, as well as posteriorly, respectively. The fascia may be harvested for reconstruction of the dural defect, and the skull base. Here's the elevation of the temporalis muscle. Here's the root of sarcoma. Here's the mastoid groove. A burr hole is placed at the junction of the squamous, and prior to mastoid sutures. Here, you can see the burr hole at the junction of these two suture lines. This maneuver should expose the dura just above the transverse-sigmoid junction. Here, you can see the location of the junction. Next, the burr hole is placed just below the transverse sinus or the posterior fossa dura. You can see the burr hole there. Additional two burr holes are placed on both sides of the transverse sinus more medially in this area. Here, you can see placement of two additional burr holes, straddling the transverse sinus. These burr holes allow dissection of the venous sinuses from the inner aspect of the calvarium. A lumbar drain is traditionally used during the operation to relax the dura and allow it's effective mobilization away from the inner table of the bone. The burr holes are relatively generous. The bone flap is elevated, additional burr holes may be necessary to protect the dura. Obviously, this initial burr hole should not be inferior enough to penetrate the petrous bone. As you can see, the craniotomy bony cuts over the dural venous sinuses, are performed using a B1 without a footplate to avoid any risk of injury from the footplate to the dural sinuses. Same technique is performed over the transverse sinus. The bone flap is subsequently elevated. Next, the mastoidectomy, allows exposure of the presigmoid dura. Small islands of bone, very thin ones, shells of thin bone may be left over the sigmoid sinus to protect its lumen and avoid any injury to its roof. Here, you can see extension of the mastoidectomy and exposure of the air cells, the antrum will be in view in a moment. The appearance of the cortical bone signifies the presence of the nearby semicircular canals, that should be protected. Here, you can see the antrum, the cortical bone over the semicircular canals, the sigmoid sinus. We've continue remove all the bone over the presigmoid dura while protecting the jugular bulb. And pulmonary irrigation is used. You can see the area of the presigmoid dura. Some of the bones of the inner ear may be exposed and should be left alone as much as possible. You can see the cortical bone over the semicircular canals. This cortical bone is filtered out, without violating the membranous portion of this semicircular canals. This additional bony removal provides ample amount of space to enter the presigmoid dura. The tentorium is cut, obviously just posterior to the petrous ridge. The fourth nerve is protected, the edge of the tentorium is identified, and the nerve is found before the tentorial incision is extended all the way, medially. Here, you can see the presence of the nerve, early identification of the trochlear nerve, avoids its injury. You can see that dural incision is being extended, just posterior to the point where the nerve enters the dura. Here, you can see the exposure of the ventral lateral ponds, the fourth nerve. You can also appreciate the trigeminal nerve located at this part of the dissection field. Again, this vein is also apparent, some of the branches of the superior cerebellar artery may also be evident in the region. This approach is quite versatile for resection of fibrous and vascular meningiomas within the petroclival area. Thank you.
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