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The Upper Petroclival Region as Seen Through Different Surgical Windows: An Extensive Anatomosurgical Study
05 February 2020 (online)
Background: Lesions involving the upper petroclival region—including meningiomas, vascular malformation, chordomas, chondrosarcomas, and plasmacytomas—can be approached through several different operative windows. Given the complex anatomy of the upper petroclival region, including retrosellar area and interpeduncular fossa, it is essential to understand the conventional and topographic anatomy of this region from different surgical perspectives as well as the complex surrounding neurovasculature. We describe the surgical anatomy of the upper petroclival region and present an analytical evaluation of the degree of exposure provided by several different surgical approaches.
Methods: Using 12 cadaveric specimens (24 sides), subfrontal, pterional, fronto-orbitozygomatic, middle fossa anterior transpetrosal, subtemporal, translabyrinthine, and retrosigmoid approaches were performed. The anterior and antero-lateral approaches were extended by anterior and posterior clinoidectomies and unroofing of the optic canal, in addition to other periclinoid and pericavernous maneuvers. The subtemporal and middle fossa approaches were extended by incising the tentorium. To quantity exposure, the upper petroclival region was divided into four compartments by an axial plane passing along the petrous ridges and a sagittal plane passing through the lateral border of the posterior clinoid process, including the lateral and medial supra- and infratentorial compartments. The neurovascular structures occupying each compartment were described and evaluated analyzing degree of exposure and surgical accessibility and maneuverability throughout the different approaches.
Results: The anterior approaches provided wide exposure of the upper petroclival region, but the deep trajectory and number of neurovascular structures encountered limited maneuverability, whereas the anterolateral approaches offered adequate visualization and maneuverability of the surgical targets. Though, the narrow surgical corridors provided by the pterional and fronto-orbitozygomatic approaches without pericavernous maneuvers did not offer the same surgical maneuverability. The lateral approaches required significant cerebral retraction, but the subtemporal approach provided the most direct corridor to the basilar apex. The retrosigmoid approach did not provide visualization of the interpeduncular fossa but allowed for good visualization of the region lateral to CN III, although it involved deep corridors, significant cerebellar retraction, and limited surgical maneuverability.
Conclusion: Surgical approach selection to the upper petroclival region depends upon the size, nature, and general location of the lesion, as well as on the capability of the particular approach to better expose the area of interest. Adequate preparation and dissection of the surgical corridors whether extradural as initial preparation for a combined intraextradural approach or as the main avenue of surgical exposure, widens the available working space, and facilitates access to the upper petroclival region. While the subtemporal approach provides the most direct access to the upper clivus, the limitations and pitfalls of temporal lobe retraction should be carefully considered.