Supplemental Methods



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The Combined Subtemporal - Transfacial Approach

Supplemental Methods
Pre-operative evaluation consists of MRI of the sinuses and skull base with gadolinium contrast and high-resolution CT without contrast. These imaging studies were performed using a high resolution navigation protocol, allowing these studies to be used with intraoperative stereotactic navigation system. Then, within one week of the surgical date, every patient undergoes angiography with embolization of the extracranial feeding vessels. Since the patient stays in the hospital for monitoring until the surgery, this procedure is ideally performed the day before surgery. It should be noted that after the embolization procedure, almost universally, the physician who performed the embolization points out that even though they could not embolize the intracranial feeding vessels, >90% of the tumor vasculature was controlled. Regardless, our experience indicates that these Stage IVb tumors will bleed extensively from its cut surfaces during the resection.
On the day of surgery, the first step is to perform a modified cranio-orbito-zygomatic approach. This is performed in an extradural fashion by a neurotologist, a neurosurgeon, or a neurotology/neurosurgery team. A standard incision is used (Fig 1a). Then, the skin and temporo-parietal fascia are lifted off of the skull, while the temporalis muscle is left in place (Fig 1b). Care must be taken when elevating over the zygoma not to damage the frontal branch of the facial nerve. To do this safely, the posterior aspect of the zygoma (the root) is identified first. A Freer elevator is then used to carefully elevate the periosteum off of the zygoma starting from its medial/superior surface, dissecting inferiorly until reaching the insertion of the masseter muscle. This is continued anteriorly all the way to expose the lateral orbital rim (i.e. the fronto-zygomatic process).
The zygoma is then cut with a sagittal saw posteriorly and anteriorly, and removed. It is placed in moist gauze on the back table, for re-fixation at the end of the procedure. The temporalis muscle is then elevated off of the skull. It is left attached inferiorly to the coronoid process of the mandible and reflected. The lateral and superior periorbita is released from its attachments to the orbital periosteum. Care is taken to preserve the supraorbital nerve.
Burr holes are then drilled (Fig 1c). The first burr hole is created at the keyhole (the junction of the lateral orbit, the anterior cranial fossa, and the middle cranial fossa). To find this location, large cutting and diamond burrs can be used in this region to precisely locate this trifurcation point. The locations of the other burr holes are less critical. The craniotomy can typically be reduced in size somewhat if the tumor does not involve the orbital apex. In this case, only the anterior portion of the middle fossa dura is necessary to expose; the anterior fossa dura and periorbita do not need to be uncovered. A craniotome is then used to turn the bone flap.
Malleable retractors are then used to judiciously elevate the contents of the middle cranial fossa and retract the temporal horn. Dissection is performed in an extradural fashion to reach foramen ovale, foramen rotundum, and the gasserian ganglion (Fig 1d). Characteristically, tumor will be visible at this point as it extends through the eroded & enlarged foramen ovale and distends cranial nerves V2 and V3 outwards. V2 and V3 are divided at the level of their foramina with a scissors and bipolar cautery. Bleeding can be expected to occur from this point on. While the active bleeding is not heavy, it is persistent and the total volume of blood loss accumulates quickly. Thus, it is wise to warn the anesthesiologist to monitor this closely and transfuse early. However, it is important to note that the application of Surgicel (or other hemostatic agents), a cottonoid patty, and pressure can be used to control the bleeding at any time.
The dissection is carried medially, using the bipolar to separate the superior tumor extension from the dura (Fig 2). The lateral aspect of the cavernous sinus is reached when the amount of bleeding increases substantially and openings in the dura reveal an intraluminal space. Resection must stop at this juncture in order to prevent injury to the CN III, IV, and VI, as well as the internal carotid artery. By this point, the bony circumference of the hole in the skull base should be fully delineated. Together with this, the ongoing cauterization with the bipolar forceps will have shrunk the tumor into the infratemporal fossa, thus separating it from the intracranial space.
While one could stop the subtemporal, lateral approach here, it is desirable to resect as much tumor as possible through the defect in the skull base. By elevating the tumor off of the underside of the bony skull base, reaching through the enlarged foramen ovale, many of the remaining intracranial feeding vessels that originate from the skull base (and which derive from the internal carotid artery) are divided. Much of this is done in a semi-blind fashion, and substantial amounts of Surgicel are placed into this space to push the tumor mass anteriorly off of the skull base.
Finally, the retractors are removed, the bone flap is plated back in place, the temporalis muscle is sutured to the edges of the periosteum, the zygomatic arch is plated, and the wound is closed. An anterior, transfacial approach is then used to resect the remaining tumor, as it has essentially been transformed from a Stage IVb to a Stage IIIa tumor (extension into orbit or infratemporal fossa without intracranial extension). The selection of the approach is up to the surgeon, but either an endoscopic or an open procedure can be chosen. The mass of Surgicel that was left between the tumor and the skull base forms a nice protective layer that defines the dural margin and informs the surgeon performing the anterior approach not to proceed further superiorly. The anterior approach can be performed either the same day as the lateral approach, or within the next several days, depending upon the level of blood loss that has occurred up to this point, patient hemodynamics, the time of day, and the desire of the surgical and anesthesiology teams.




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