January 19, 2016
Let's review the basic principles of anterior petrosectomy or the anterior petrosal approach, briefly using a cadaveric dissection. You can see the incision in this cadaver is relatively curvilinear. I usually use a straight incision just anterior to the ear, while protecting the superficial temporal artery in the cadaver because of the stiffness of this scalp, a larger scalp flap was elevated. You can see the temporalis muscle is being reflected anteriorly. A bone flap was also elevated. You can see the root of the zygoma in this case, the size of the bone flap which is about 2/3 anterior to the EAC and 1/3 posterior. However, the location of that bone flap has to be adjusted to their location of the pathology and its relationship to the internal auditory canal. And you can see the root of the zygoma re-identified here. The elevation of the scalp flap, mastoid aerosols have to be waxed. If they are open during the craniotomy, I use a lumbar drain during the surgery and make sure that dura remains intact during the elevation of the bone flap. Here the overhanging bone over the middle fossa will be drilled away so an unobstructed view toward the middle fossa floor is possible. It really is usually effective during the operation. The air cells are invariably entered. Next, the middle meningeal artery is transected at the level of frame and spinosum and the dura is elevated from poster to enter direction to protect the greater superficial betrothal nerve. Here, you can see the drilling over the area of the petrous apex. CT or navigation can assist with wander removal during the surgery. The traditional landmarks are as follows, the anterior border of the resection is just posterior to the Douro over the mandibular branch of the trigeminal nerve. The lateral border of only resection is the greatest professional petrosal nerve. And the poster order of the only removal consists of the auditory canal and cochlea. You can see the bone can be quite dense in this area. When you remove all us continued, fixer tractors are generally necessary, pointed and move all this continue until the dura of the poster fossa is encountered. As you can see here, the IC is protected. In this case, I inadvertently toward the door over the poster fossa in this cadaver because of the attenuation of the dura. And you can see now the dura in the middle fossa is opened in a T fashion and disconnected to the opening within the posterior fossa. The trigeminal nerve is trans-versing just at the junction of the posterior and middle faucet dura along the posterior aspect of the cavernous sinus and Durham opening has to be carefully conducted in that area to avoid any injury to the trigeminal nerve. Here's the door opening and the T fashion tour the poster fossa. Here, you can see that trigeminal nerve that was protected during the dural opening and the extend of the exposure toward the ventral lateral aspect of the poster fossa. Again, here's the trigeminal nerve. I'll stop the video right there to show you again, the opening from the middle fossa toward the posterior fossa, the antero lateral aspect of the brain stem the location of the trigeminal nerve and how it can be quite hidden within the dura of the middle fossa, joining the dura of the posture fossa. Thank you.
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