Avoiding Injury to Cranial Nerves III, IV, and VI in Skull Base Surgery: Anatomic Perspectives in Anterolateral Approaches

Objective: Understanding the anatomy of cranial nerves (CN) III, IV, and VI from different surgical perspectives, as well as their relationships with surrounding structures, is crucial for selecting the most appropriate surgical approach and identifying potentially dangerous surgical maneuvers. We describe the intracranial courses of CN III, IV, and VI as observed through different anterolateral neurosurgical approaches and evaluate the degrees of exposure achieved in each approach. Study Design: Cadaveric. Material and Methods: We divided the CN III, IV, and VI into pre- and postclival segments and performed approaches to expose their postclival portions—including the lateral orbitotomy, supraorbital keyhole, unilateral and bilateral frontal transbasal, pterional, frontoorbitozygomatic, and subtemporal approaches on five cadaveric heads (10 sides). Degrees of exposure were scored by three surgeons in each approach. Results: The postclival segments of the nerves were exposed to varying degrees through the surgical approaches considered. Some of the surgical corridors exposed the nerves to the likelihood of injury more than others. The risk of direct nerve injury was high in the cavernous courses of CN III and IV and the course of all three nerves inside the superior orbital fissure due to the limited maneuverability in these areas. Conclusion: An exhaustive anatomia surgical comparative analysis is important for selecting the most appropriate approach and the safest surgical steps.