Cadaver-Orbitozygomatic Craniotomy and Extradural Clinoidectomy
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Let's re-review the orbitozygomatic osteotomy and extradural clinoidectomy via a cadaver dissection. Based on the location of the pathology relative to the midline, the head is turned more contralateral curvilinear incision is completed all the way to the contralateral mid pupillary line. And if possible, the superficial temporal artery is protected. Next, is subgaleal dissection is completed for subfascial mobilization of temporalis muscle. Here's the nasion. supraorbital nerve is mobilized out of its groove. The subfascial technique is used to mobilize the fat pad. In other words, the superficial and deep temporal fascia are mobilized along with the fat pad to protect the branches of their frontalis nerve. Here's temporalis muscle. Keyhole is located here. The frontal process of zygoma is exposed in a subperiosteal fashion. This is a modified one-piece orbitozygomatic craniotomy, a full orbitozygomatic craniotomy is not necessary. A cuff of muscle and fascia is left over the superior temporal line to facilitate adequate closure and approximation of the temporalis muscle. The temporalis muscle is then mobilized inferiorly out of our working zone around the keyhole. Here's the area of the keyhole, temporalis muscle essentially mobilized inferiorly in a slightly posteriorly. Here's the frontozygomatic suture. The initial burr hole is placed at the exact side of the McCarty's keyhole. In other words, a few millimeters above and a few millimeters posterior to the frontozygomatic suture. Drilling is conducted at 45 degrees against the surface of the skull. The bone at the roof of the orbit is exposed. The periorbital exposed as well as the dural of the frontal lobe. All three structures should be exposed within the burr hole. Accurate placement of this burr hole is quite important for efficient and accurate completion of the one-piece modified orbital psychosomatic craniotomy. First osteotomy involves the frontal bone, starting from the posterior burr hole, reaching all the way to the level of the orbital rim. I advanced the drill all the way until further progress is not possible. In other words, the foot plate touches the rim of the orbit. The drill can then be lean more forward, turned around it's own axis, creating small amount of opening within the bone for the heel of the foot plate to be removed first. This also creates some space for the osteotomy at the rim of the orbit later. You can see the osteotomy at the level of the orbital rim. This part of the bone is quite thick. Next another osteotomy is completed over the pterion and the latter aspect of the sphenoid wing. Next the osteotomy across the frontal process of zygoma is completed. The periorator is protected. This art is the joins the bony cut over the area the pterion. The next more important maneuver involves using an osteotome to fracture the hoof of the orbits. Alternatively, a small osteotome can be used through the keyhole to cut across the orbital rim. Next, the lateral five millimeter of the meningo-orbital band is cut and the doodle over the anterior aspect of the temple bone is reflected. This maneuver nicely exposes the clinoid process. The clinoid process is hollowed out and the optic nerve is unroofed. Here's the optic nerve that was unroofed, here's the remainder of the clinoid process that was cored out. After the clinoid process was removed, you can see the optic nerve, the carotid artery within the cavernous sinus. Portion of the orbital roof may also be resected for additional unobstructed view of the subfrontal trajectory after the dural opening. Here you can see the final product of an orbitozygomatic craniotomy which involves removal of the bone over the roof of the orbit as well as an extradural clinoidectomy and all these maneuvers allow an unobstructed and expanded view toward the parasellar areas. Thank you.
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