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Pterional Craniotomy: Nuances and Pitfalls

November 11, 2018

Transcript

Efficient performance of Pterional Craniotomy is important and this video reviews technical nuances and pitfalls for this operative corridor. Starting with patient positioning, we will discuss the incision. Incision starts just the centimeter into the tragus and stays essentially behind the hair line. Extension of incision more posterior over the frontal lobe is not necessary as the surgical target often resides within the subfrontal area for the pterional approach. Incision starts again enter to the tragus, travels just perpendicular to the superior temporal line. Then stays behind the hairline right afterwards and often can extend slightly past the midline toward the contralateral mid pupillary line. You can see the single pin behind the ear in order to provide a large unobstructed space for performance of the craniotomy. Again, the incision is very much the behind hairline and further posterior extension is not necessary. The malar eminence is the highest point in positioning of the head. The belly of the knife is used to start the incision from the frontal side of the incision. The incision stops where the temporal starts. Reyneke clips may be used for hemostasis. Next, a white spatula is used to bluntly dissect over the temporalis fascia and the knife can be used to efficiently open the incision while preserving the superficial temporal artery branches. Bipolar cautery is used for coagulation of larger caliber leaders of the scalp. Next, sharp dissection over the temporalis fascia is conducted until the keyhole is palpated. The branches of the frontalis nerve travel here, and one should not cut perpendicular to them. Here is palpating the keyhole or the final process of zygoma. Here is the fat pad. A subfascial technique may be used to protect the frontalis nerves. Again, you can see the use of monopolar electrocautery to cut parallel to the frontalis nerve and not perpendicular in this direction. The nerves travel in the superficial fascia of the fat pad and not within the fat pad. Again, not cutting perpendicular to the nerves is important for preservation of frontalis branches. A cuff of temporalis muscle is left behind for closure. Next, I undermine the fat pad. The muscle is further cut more posteriorly placed under tension. Extension to the root of zygoma is not necessary typically. Blunt dissection of the deep temporalis fascia may be performed to minimize the risk of temporalis atrophy after surgery. Single burr hole is placed just below the superior temporal line more posteriorly. I do not place burr hole in the area of the keyhole for a number of reasons. Number 1 is for cosmetic satisfaction and preservation of bone in the area of the keyhole. This single large keyhole is covered by the temporalis muscle and is therefore cosmetically more appealing. Next, you can see the Number 3 Penfield dissector can be used to widely dissect the dura all the way to the area of the lateral aspect of sphenoidal wing. I avoid dissecting over the areas where the craniotomy will not be performed. In other words, beyond the edges of the craniotomy to avoid epidural bleeding. Here, you can see how the dissector can be used very strategically to dissect the dura from underneath the skull surface effectively. The drill B1 with a foot plate is used to conduct a temporal osteotomy. The drill is advanced all the way to the lateral aspect of the sphenoid wing and then turn around itself 180 degrees to create enough space within the bone for the drill to be removed effectively and without much efforts. Now, the frontal osteotomy bony cut is completed. You can see that the P1 bit is kept perpendicular to the surface of the skull at all times. It may be toggled slightly to dissect the dura away from the inner surface of the skull bone so you can seem significant exposure of the frontal. Though be, it's not usually necessary for a subfrontal approach. Next, a B1 without a footplate is used to conduct additional osteotomy over the sphenoid wing and slightly over the area of the supraorbital region. This allows a very flushed trajectory toward the roof of the orbit without leaving a ledge of bone over the area of the supraorbital region. This is a critical area which is typically the operative trajectory which should remain unobstructed by the ledge of the bone. Next, the bone flap is cracked at its based over the lateral aspect of sphenoidal wing. You can see a very nice bony cut parallel to the roof of the orbit. The bone over the latter aspect of sphenoid wing will also be removed using celeron drawers. First, the bone is dissected away using a Number 1 Penfield dissector. Here, you can see the thick bone or the area of this supraorbital region that was able to be cut effectively using the B1 without a foot plate. This improves the efficiency of the procedure rather than leaving an edge of bone here and then spending significant amount of time removing the edge of the bone with another trail later. Two tack-up stitches are placed. One over the temporal region and one over the frontal region. I use gelfoam powder soaked in thrombin to again, efficiently control epidural bleeding specially along the edges of the craniotomy and from the cancellous bone. Here again, is removal of the lateral aspect of the sphenoid wing. A critical part of this craniotomy performance is making sure that the bone over the roof of the orbit is drilled so that, a very flat unobstructed trajectory towards the anterior skull base is reached. This important step can obviate the use of orbital zygomatic craniotomy for a number of reasons around the circle of Willis. Then the periorbita is not exposed. Just the bone is drilled until a very thin sheet of bone is left over the orbit. A finer drill bit maybe use to continue drilling in this area. The lateral aspect of sphenoid wing may be trailed all the way to the edge of the superior orbital fissure. Here, you can see the lateral aspect of the clinoid process may be exposed. Although, this video shows part of the extradural clinoidectomy. This clinoidectomy may not be needed in every case and should be tailored. You can see the lateral aspect of the orbital meningeal band was transected for about a millimeter or so. This is also called the frontal temporal dural fault. And then, the dura is elevated gently from the dura that covers the lateral aspect of the cavernous sinus. This nicely exposes the clinoid process which may be drilled if necessary. This patient was suffering from Asymptomatic Middle Sphenoid Meningioma. And therefore, an extradural clinoidectomy was initially performed to decompress the optic nerve early on during the procedure. Here, you can see the very flat trajectory by drilling the bone over the roof of the orbit. Here you can, the performance of the extradural clinoidectomy and optic nerve decompression. Retractors are often unnecessary as long as the dura has been mobilized at the level of the supraorbital fissure. Here, you can see the optic nerve. The rest of the bone is gently mobilized away from the nerve while minimizing the use of the drill directly over the dura of the nerve. Now, the dura may be opened in a curvilinear fashion. I leave fair amount of dura over the brain intact, so that the frontal lobe is protected. As you can see the dural opening is just over the area where this up frontal operative trajectory is used for. You can see the tumor extending laterally over the dura of the Sylvian fissure. And the rest of the procedure can be conducted as necessary for tumor removal. I think this video is a nice example of how the pterional craniotomy can be conducted efficiently. I have tried to exclude a number of steps that may be unnecessary. However, further steps may be needed for performance of orbital zygomatic craniotomy which will be covered in a different video. Thank you.

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