Download The Combined Subtemporal - Transfacial Approach Supplemental

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