Develop your exposure working medial to lateral.Drill deep troughs 270 degrees around the IAC, down to the level of the posterior fossa dura.Lower the meatal plane over the IAC until it is well-defined.The IAC is located 60° anterior to the blue lined SSCC.The Stenvers x-ray will demonstrate the amount of bone overlying the semicircular canal (SSCC).The SSCC will be perpendicular to the petrous ridge.Begin drilling using a 4-0 diamond burr over the arcuate eminence to identify the location of the superior semicircular canal.Place the House-Urban retractor under the lip of the petrous ridge at the anticipated location of the IAC (based upon the arcuate eminence).Brisk bleeding from the middle meningeal artery at the foramen spinosum may be encountered and can be controlled with bone wax and Oxycel packing.Use cottonoids anteriorly and posteriorly for dural retraction during elevation.Identify the arcuate eminence, GSPN, and petrous ridge.Elevate the dura along the floor of the middle cranial fossa from posterior to anterior so as not to disrupt the greater superficial petrosal nerve (GSPN).Place Oxycel cigars under the bone flap anteriorly, posteriorly, and superiorly.Circumferentially elevate the dura from the overlying cranium, using the bipolar cautery liberally to stop bleeding from the dura.Check exposure: if the bone window is not flush with the tegmen, remove excess bone with rongeur or drill.Elevate bone flap off of dural with Joker elevator.Mark bone flap to ensure easy and properly oriented replacement at end of case.Branches of the middle meningeal artery will be encountered, which are controlled with bone wax or bipolar cautery.Use diamond 4 mm burr, to remove the final layer of bone over the dura.Use a 4 mm (BJG) or 5 mm (MRH) cutting burr to remove the majority of the bone.Hyperventilate patient to end tidal CO2 of 30.Have anesthesiologist administer 0.4 grams/kg of mannitol now.
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