Introduction: The petroclival region and cerebellopontine angle represent areas of anatomical complexity
at the skull base. An adequate access route must be prioritized, limiting the potential
injury of critical neurovascular structures. The transcochlear approach is a lateral
corridor that offers suitable exposure and control of structures such as the petrous
internal carotid artery. However, this procedure must be carefully indicated due to
the functional losses it entails, including hearing loss and, possibly, facial nerve
paralysis. The endoscopic endonasal approach, on the other hand, presents the advantage
of limiting brain retraction and improving time of recovery.
Method: Four embalmed human cadaveric specimens were used for anatomical dissection. The
petroclival region was exposed on each side through the transcochlear and endocopic
endonasal transclival approaches. Through imaging-based navigation, stereotactic annotation
points were collected. The corridor’s volume was assessed for both the endoscopic
and lateral approach. The area of exposure at the ventral aspect of the pons was measured,
along with a differentiation of the areas lateral and medial to cranial nerve VI.
The length of cranial nerves VI, IX, and X, and basilar artery was determined. Angles
of attack were collected for critical neurovascular structures on each of the exposed
surgical fields.
Results: An endoscopic endonasal transclival and transcochlear approach were dissected bilaterally
on each specimen. The endoscopic endonasal corridor provided greater anteromedial
exposure in relation to cranial nerve VI, improving maneuverability for lesions crossing
the midline. The transcochlear approach provided greater exposure posterolateral to
cranial nerve VI, in addition to exposure of the cerebellopontine angle. Maneuverability
around cranial nerve VI at Dorello’s canal was improved through the lateral corridor
given its direct trajectory for instrumentation and visualization. Maneuverability
around cranial nerves IX and X was also favored by the transcochlear approach.
Conclusion: The endoscopic endonasal approach provides adequate exposure anteromedial to cranial
nerve VI, with significantly less bone drilling and anatomy distortion. Lateral corridors
should be considered when lesions have considerable posterolateral extension. The
transcochlear approach provides adequate exposure laterally, with additional control
of the petrous carotid, yet it completely abolishes hearing function and patient selection
should be carefully planned.
