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

OBJECTIVE: Lesions situated posterolaterally along the mesencephalon present neurosurgeons with a special challenge. The midline and paramedian variations of the supracerebellar infratentorial approaches do not adequately expose this region. The subtemporal approach risks injury to the vein of Labbe. An extreme lateral supracerebellar infratentorial approach with more radical resection of bone superiorly and laterally, and skeletonization of the sigmoid and transverse sinuses, was used to approach lesions at this location in eight patients. The clinical series is presented, and the regional surgical anatomy is described. METHODS: Five cavernous malformations, two juvenile pilocytic astrocytomas, and one peripheral superior cerebellar artery aneurysm located in this region were approached in eight patients. In this extreme lateral approach, the sigmoid sinus is unroofed more superiorly and the bone flap includes not only a posterior fossa craniotomy but also a portion that extends just above the transverse sinus. The dural opening is based along the transverse and sigmoid sinuses. After the cerebrospinal fluid has been drained, the lateral aspect of the brainstem is approached via the cerebellar surface. A proximal tentorial incision offers additional rostral exposure where needed. RESULTS: Seven patients in this series underwent successful resection of their lesion. The remaining patient's aneurysm was clipped successfully with no major complications. CONCLUSION: The extreme lateral supracerebellar infratentorial approach differs from the midline and paramedian supracerebellar infratentorial variants in the area of exposure, patient positioning, and location of the craniotomy. The technique is effective for approaching the posterolateral mesencephalon.