Quantitative Analysis of Exposure of Staged Orbitozygomatic and Retrosigmoid Craniotomies for Lesions of the Petrous Apex and Clivus with Supratentorial and Infratentorial Extension

Introduction: Alternatives to transpetrosal approaches in the management of petroclival tumors include two-stage approaches utilizing orbitozygomatic (OZ) and retrosigmoid (RS) craniotomies. The aim of this project was to investigate the supratentorial and infratentorial exposure of the clivus obtained by this staged approach.

Methods: Formalin-fixed silicon-injected specimens underwent stereotactic imaging. Six paired OZ and RS craniotomies were performed. Areas of exposure were determined utilizing neuronavigation.

Results: The area of exposure of the parasellar region and clivus via OZ craniotomy was 640 ± 75 mm. Excellent visualization of the parasellar region, cavernous sinus, and upper cranial nerves was accomplished. The brainstem corresponding to the superior one quarter of the clivus was visualized. The area of exposure of the clivus and petrous bone through the RS was 1930 ± 250 mm. There was a region of overlap in exposure between the craniotomies in the upper quarter of the clivus.

Conclusions: Significant exposure of the parasellar region, clivus, and surrounding bony landmarks can be obtained by a strategy of staged OZ and RS craniotomies. The primary limitation is exposure of the contralateral half of the clivus from its superior quarter to the foramen magnum. This strategy represents an alternative to transpetrosal approaches for petroclival lesions.