Technique

Previous reports2–4 have described this procedure in detail. Here, we offer a stepwise depiction of the technique. The head is secured in a lateral supine position. A “U”-shaped incision is made above the ear ( Fig. 30.1a ) and a temporalis fascia flap is raised to facilitate wound closure at the end of the procedure. The temporal fascia is dissected from the temporal muscle and is transposed caudally, while the temporal muscle is transposed anteriorly ( Fig. 30.1b ). A craniotomy is performed with its base parallel to the zygomatic arch and the floor of the middle fossa, just above the root of the zygoma and the mastoid crest ( Fig. 30.1c ). The periosteal dura is carefully dissected from the temporal bone. The foramen spinosum is identified and the middle meningeal artery is located, coagulated, and cut with microscissors ( Fig. 30.1d ). Next, the foramen ovale is seen anteriorly. The bony depression, along with the greater superficial petrosal nerve (GSPN), marks the anterolateral boundary of the drilling area, which is further bound by the arcuate eminence posterolaterally, the internal auditory canal (IAC) inferolaterally, the carotid canal inferiorly, and the trigeminal impression anteromedially ( Fig. 30.1e ). After drilling the petrous pyramid ( Fig. 30.1f ), the dura of the posterior fossa is opened, finding the lateral aspect of the pons and the root of the trigeminal nerve ( Fig. 30.1g ). A T-shaped cut is made over the dura of the temporal lobe and along the superior petrosal sinus (SPS), showing the edge of the tentorium. The SPS is coagulated, cut with microscissors, and sutured at both ends. The tentorium itself is then cut until the tentorial notch is open. This step is performed with care to avoid injury to the trochlear nerve, which runs beneath the medial edge of the tentorium ( Fig. 30.1h ), and completes the exposure. ( Fig. 30.1j )