Extreme lateral supracerebellar infratentorial approach to the posterolateral mesencephalon: Technique and clinical experience

OBJECTIVE: Lesions situated posterolaterally along the mesencephalon presen t neurosurgeons with a special challenge. The midline and paramedian variat ions of the supracerebellar infratentorial approaches do not adequately exp ose this region. The subtemporal approach risks injury to the vein of Labbe . An extreme lateral supracerebellar infratentorial approach with more radi cal resection of bone superiorly and laterally, and skeletonization of the sigmoid and transverse sinuses, was used to approach lesions at this locati on in eight patients. The clinical series is presented, and the regional su rgical anatomy is described. METHODS: Five cavernous malformations, two juvenile pilocytic astrocytomas, and one peripheral superior cerebellar artery aneurysm located in this reg ion were approached in eight patients. In this extreme lateral approach, th e sigmoid sinus is unroofed more superiorly and the bone flap includes not only a posterior fossa craniotomy but also a portion that extends just abov e the transverse sinus. The dural opening is based along the transverse and sigmoid sinuses. After the cerebrospinal fluid has been drained, the later al aspect of the brainstem is approached via the cerebellar surface. A prox imal tentorial incision offers additional rostral exposure where needed. RESULTS: Seven patients in this series underwent successful resection of th eir lesion. The remaining patient's aneurysm was clipped successfully with no major complications. CONCLUSION: The extreme lateral supracerebellar infratentorial approach dif fers from the midline and paramedian supracerebellar infratentorial variant s in the area of exposure, patient positioning, and location of the craniot omy. The technique is effective for approaching the posterolateral mesencep halon.