Anatomo-Surgical Classification of Endoscopic Endonasal Transclival Approaches

Aim of the Study: This study provides a simple anatomo-surgical classification for the endonasal endoscopic transclival approach to skull base pathologies based on our experience.

Methods: Based on “the ventral rule of three” we categorized the transclival approaches into upper, middle, and lower clivus approaches, or a combination of the three. We described the surgical landmarks, neurovascular structures at risk and the area of exposure for each anatomical corridor. After retrospectively reviewing the series of approaches at our institution over the last 10 years we observed the types of pathology that each approach transclival is most suited for.

Results: We identified 156 cases, of which 45 were chordomas, 40 were meningiomas, 11 were chondrosarcomas, 10 were craniopharyngiomas, and 50 were miscellaneous pathologies.

The superior transclival approach was found to be useful for retroinfundibular craniopharyngiomas and upper extension of other tumors. This corridor goes from the posterior clinoids to the sellar floor and is limited laterally by the parasellar ICA. It provides access to the interpeduncular cistern and its contents.

The middle transclival approach was used particularly for clival chordomas, chondrosarcomas, and petroclival meningiomas. It extends from the sellar floor to the lower face of the sphenoid sinus and is limited laterally by the paraclival ICA. This corridor gives access to the prepontine cistern with its contents.

The inferior transclival approach was ideally suited for inferior extension of chordomas and foramen magnum meningiomas. The corridor goes from the lower face of the sphenoid sinus to the foramen magnum. It is limited laterosuperiorly by the lacerum segment of the ICA and lateroinferiorly by the occipital condyles. It exposes the premedullary cistern and its contents.

Conclusion: The classification described provides a simple and schematic way of selecting the best corridor for a particular lesion based on its location along the clivus, anticipating and thus minimizing the potential complications.