The anterior subtemporal, medial transpetrosal approach to the upper basilar artery and ponto-mesencephalic junction

OBJECTIVE: To describe and anatomically analyze the amount of exposure provided by an anterior subtemporal, medial transpetrosal approach to access the upper third of the basilar artery, ventral mesencephalon, pens, and posterior cavernous sinus. PATIENTS AND METHODS: The outcomes of six patients who underwent surgical treatment via the anterior subtemporal, medial transpetrosal approach at our institution during the past 2 years were reviewed. The series included three patients with subarachnoid hemorrhage from low-lying basilar apex aneurysms, one patient with intraparenchymal hemorrhage from a pontine cavernous malformation, and two patients with slowly progressive cranial neuropathies secondary to petroclival tumors. Thirty dry temporal bone specimens were also measured to quantify the height of petrous bone resection and added proximal basilar artery exposure. RESULTS: The surgical exposure was greatly enhanced in each instance, allowing each lesion to be treated in a straightforward manner with minimal added morbidity (one trochlear nerve palsy, one worsening of a preexistent oculomotor nerve palsy). Our subsequent morphometric analysis indicates that an additional 1 to 1.5 cm of basilar artery, clivus, and pens exposure over that of a standard anterior subtemporal approach is provided by this technique. CONCLUSION: This approach combines the wide view of the subtemporal approach with the more proximal exposure afforded by a medial petrosectomy. The widened visualization of the ventral pens and mesencephalon minimizes cranial nerve morbidity, greatly facilitates dissection of low-lying aneurysms, and provides proximal basilar artery control that would otherwise be obscured by the petrous ridge.