July 07, 2014
Here are the basics for performance of a temporal craniotomy. This is a 66 year old female with subtle speech difficulty who on MRI evaluation was noted to have a heterogeneously enhancing mass, within the temporal lobe, consistent with a GBM. She underwent resection of the mass. You can see the positioning of the patient on the operating room table. Supine position was used. Horseshoe incision was marked, centered above the ear, with the extent of the incision to the level of the root of zygoma. Placement of this skull clamp is also shown. Let's go ahead and discuss the incision, the scalp and muscle reflection and completion of the craniotomy. The belly of the knife is used. Raney clips are applied for hemostasis. The muscle may be cut in one layer along with the scalp or in a separate layer. The knife is used perpendicular to the surface of the skull. The temporalis muscle is mobilized in one layer along with a scalp. Monopolar cautery is used to disconnect the muscle from the superior temporal line. The muscle is mobilized as inferiorly as possible, while exposing the root of zygoma. The root of zygoma, identifies the floor of the middle fossa. Here's the palpation of the root of zygoma in this case. And here is anterior, here is posterior. Fish hooks are used, so that the muscle is kept out of our working zone. Two burr holes are placed, one along the posterior aspect of our bony exposure, and one just above the root of zygoma. The dura is generously mobilized away from the inner aspect of the cavity. Generous burr holes are quite effective for reaching the entire surface of the dura that has to be mobilized. Here's the second burr hole. It's important to remember that the middle fossa floor slopes superiorly from the anterior to posterior direction. This fact should be remembered as the craniotomy along the inferior aspect of the bone work is completed. First I complete the more superior cuts, the drill is used, to complete the bone cut, and it should remain perpendicular to the surface of the skull. Any injury to the vein of Labbé during performance of the posterior Burr hole, or the craniotomy should be avoided. If the dura is very adherent, especially in older individuals, multiple burr holes may be necessary to maintain the integrity of the dura during the bone work. The inferior bone cut is quite important. We want to stay as close to the level of the middle fossa floor as possible. If the drill can not be advanced further, the bony cut can be conducted through the posterior burr hole connecting to the cut from the anterior burr hole. Now the bone flap is elevated. Some of the air cells that are violated should be well waxed and epidural hemostasis is secured. I use thrombin soaked gel foam for reaching epidural hemostasis. The dura is open in a curvilinear fashion based over the floor of the middle fossa. Here's the portion of the tumor reaching the pial surface. The dura is mobilized out of our working zone via retention sutures, placed at the root of the dura closer to the edge of the craniotomy. Now we can proceed with tumor resection. Again any of the veins along the posterior aspect of the dural opening should be protected since the vein of Labbé is expected to be there. Tumor removal follows standard microsurgical techniques. Following tumor removal, standard closure is completed. You can see the relatively watertight dural closure. Placement of the bone flap follows. Thank you.
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