December 02, 2015
This video describes techniques for an anterior transpetrosal approach or an anterior petrosectomy for resection of a more superiorly located petroclival meningioma. This is a 42-year old female who presented with progressive double vision, most likely related to trochlear nerve palsy. She had previous history of radiation for a brain stem glioma, that is no longer apparent, and was noted to have this meningioma along the petroclival region and most likely, as you can see a little bit more, posterior located than a traditional petroclival meningioma. The lesion does stay above the internal auditory canal and therefore is a reasonable candidate for a anterior petrosal approach. There's really no easy other approach to reach this lesion. orbitozygomatic trional approach will have limitations in terms of reaching the posterior pole of the tumor. Let's go ahead and review the very details of the anterior petrosal approach. This cover of image from Dr. Roten describes the final operative route after the petrosectomy's completed. You can see that this is right-sided approach. This is the floor of meta fossa, the greater superficial petrosal nervous. apparent here V3 is apparent here. Obviously trigeminal nerve that tentorium has been cut also reflected posteriorly. You can see the ventral lateral aspect of the brainstem, the seven and eight cranial nerve would be just about below the lip of the bone here. This is really the reach of the entropy tri-sectomy and you can see the third nerve and fourth nerve, and therefore the tumor has to be very much confined to this region. This is a very inflexible approach, and if the tumor is beyond the margins associated with the borders here, it is going to be difficult to expand this approach or customize it after the initial exposure. The most anteromedial aspect can be limited by the clivus. We'll go ahead and start with the patient positioning and linear incision is used. You can see the location of the zygoma and incision goes all the way to the lower edge of the zygoma. And it's just anterior to the ear with a hope of preserving the superficial temporal artery. The head is tilted slightly toward the floor, so gravity retraction will facilitate the position of the temporal lobe. The head is turned approximately, as you can see up to 70 degrees or possibly more to be able to get the superior sexual sinus or sexual suture nearly parallel to the floor. This linear incision is completed. One nuance that's really important is to undermine the scalp and cut the attachment of the temporalis muscle parallel to the superior temporal line in order to be able to mobilize the muscle effectively and take advantage of the linear incision to expose as much of the temporal bone as possible. A burr hole is placed as you can see at the root of the zygoma, the root of the zygoma was exposed here. This is an important landmark to assure that we're as inferior as possible. And essentially the root of the zygoma is followed, and the craniotomy is created as close to the floor of the middle fossa as possible. Here is the root of zygoma, here as you can appreciate in dislocation and lip of bone over the middle fossa is stroke away thoroughly and mastoid air cells that are potentially interred are well laxed. Longboard drain is used. This is the middle meningeal artery passing through the four-minute spinosum. This is the greater superficial petrosal nerve and posterior to anterior dissection of the dura is completed to preserve this nerve as much as possible. So location of the semicircular canals, please refer to the text of this chapter for further details about the anatomy. The middle meningeal that is quite isolated and cut. Sometimes ponal wax mixed with Surgicel is used to plug the, foremen spinosum. Here again is a the anatomy of the area, knowing that this is the, again, the greater superficial petrosal nerve to orient the two images together. You can see how I dissect from posterior to anterior. The arcuate eminence is apparent. Here is the Doppler ultrasound identifying the location of the internal quarter artery that owns a incompetent roof. Here is a start of a P-trisectomy. Here again is another kind of a image demonstrating the anatomy of the region and where we're gonna be working. Obviously we want to be able to remove this piece of the bone and protect the cochlea and the semicircular canals as much as possible. Here moving more toward the IAC, V3 enters here in just about behind the trail. internal carotid artery would be in that location Two retractors are placed to be able to mobilize the dura, but as mentioned previously, the lower membrane is very important. Here is pushing of the dura over the poster versus being exposed. We continue going and leave alone anteriorly Here, additional bone removal reaching the larger aspect of the clivus. And thin shell of bone is left behind and then gently mobilized away from the dura The internal carotid artery was not mobilized in this case, as it was unnecessary due to the location of the tumor being slightly more posteriorly. Now we're really getting to the most inferior extent of our exposure. Further drilling here essentially may not add more to the exposure as you're drilling into the clivus and essentially perpendicular to it. Here opening of the dura first parallel to the roof or parallel to the access of the middle fossa. In this situation, I gently elevated the temporal lobe and open the arachnoid membranes to achieve more relaxation, before the second cut over the dura toward the tumor was completed. Here's the edge of the tentorium we'll look for the fourth nerve before any incision is made in that area. The fourth nerve could not be found. You appreciate the antero lateral aspect of the brainstem just about here. I use a Carla knife to cut the edge of the tentorium, just where the tumor is. Often the incision is made in this location. However, in this case, because the location of the tumor was slightly unusual. I plan to do the trust and trial cut in the reverse direction in order to be able to expose the tumor effectively after the tumor has been identified. Bleeding from the posterius to the cavernous sinus can be quite annoying during transection of the tentorium and plum hemostatic agents should be used to fill in the space between the leaves of the tentorium, where the venous lakes are located. Here you can see the first cut that was made parallel to a temporal dura. The most critical part here is the fifth cranial nerve or the trigeminal nerve can be easily transected. As you can see, between the leaves of the dura as the nervous entering the poster aspect of the Cavernous Sinus. Aggressive quiet relation around the nervous avoided flow. Silver was used to again, create a temper notch between the leaves of the tentorium, where the venous lakes are located. Dura incisions are made in very small increments to assure no injury to the fifth cranial nerve. Here's the tumor being mobilized from the edge of the tentorium, working on both sides of the tentorium. This is the third nerve. Again, the anterior aspect of the tumor that's been globalized wants to border of the tumor anteriorly as identified. We can go ahead and appreciate if our dural incision within the tentorium was adequate and if further incision is necessary. So now that we have completed our super tentorial incision within the tentorium, we'll go ahead and do a separate incision in the posterior fossa dura at the area of the picture-sectomy. Now we connect the two incisions together to be able to expose the infratentorial section of the tumor here. Here now you can see the Infratentorial portion of the tumor, this is the fifth nerve, the dura and the posterior fossa, the tentorium or medially the nerve is being released from the tentorium so that I can work both above and below the nerve to remove the tumor. Here's again, the last pieces of dura along the edge of the tentorium, I was unable to find the trochlear nerve, despite my significant efforts to find the nerve Here's the tumor that was originating from the edge of the tentorium, and now that it is de vascularized, it can be debarked and dissected away from the surrounding structures. The ultrasonic aspirator is in nucleating, the tumor, which is quite fibrous. Now the arachnoid membranes are sharply cut and the tumor is mobilized. The basilar artery will be along the most posterior and medial aspect of the capsule and it's perforators that could be adhering to the tumor capsule, have to be looked for. This small operative space demands that the tumor is generously debarked before the capsule is mobilized. Here is the ventral lateral aspect of the midbrain. The tumor capsule is being mobilized away from the brain stem, and we'll be running into that rack node membranes of the basil artery. Just about in that location. You can see someone with perforators and working both above and below the trigeminal nerve to dissect the tumor without blindly pulling on the tumor fragments. The arachnoid planes against the brainstem are protected you can see here this' the basil artery and the arachnoid membranes that are sharply cut. You will see momentarily, there'll be some bleeding from the one of the perforators or the basil artery debt will be carefully managed via a piece of cotton rather than aggressive, quite relation around these vital structures. Here is more medial aspect of the tumor that is being taken away from the brain stem. There's minimal retraction on the brain stem, but rather more manipulation of the tumor capsule. Piece of cotton is used to protect the peel membranes over the brainstem. You can see the arachnoid membrane over the basil artery. There were some bleeding here that I discussed a moment ago, which I wasn't really sure if it's venous or arterial, however, all six were not used to necessarily blindly quagga late that PO of the brain stem. A piece of cotton soaked in thrombin was used to gently tap or dry the place, since the pressure of the bleeding was not very significant. You can see that the edges of the tumor very carefully inspected before they are removed. Here's the, portion of the third nerve that was adherent to the pole of the capsule, just leaving the brain stem. More debarking is performed here is working through the arachnoid membranes along the anterior aspect of the tumor. The tumor is entering the cavernous sinus at this location. And I did not pursue removal of the tumor that was located into the cavernous sinus where the tumor is being cut at the location where it entered the sinus. Here's the medial arachnoid membranes, the tumor capsules almost completely removed besides a small part in the cavernous sinus. Here's the basil of artery, a panoramic view of the ventral lateral aspect of the brain stem. This is where the tumor enter the cavernous sinus. I'm just cleaning up the edges there. So the third nerve in thrilling the cavernous sinus, and here's the funnel view of the surgery. As you can see the fifth nerve, the third nerve was, is located here, and it was elevated by the tumor. This is the ventral lateral aspect of the brainstem. This is the basilar artery, some of the perforators, really a nice view for lesions located in this area. Here again is another view. One wax was used to obliterate all the mastered aerosols along the middle fossa, and the post on prepare of MRI in this patient demonstrated gross total resection of mass. As you can see, I might expect their small amount of tumor left within the cavernous sinus, this' special recovery from surgery without any untoward effects and her diplopia, which was very mild before surgery remained stable. Thank you.
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