Endoscopic Skull Base Surgery to the Ventral Wall of the Posterior Fossa

Objective: Pathological processes in the ventral skull base of the posterior fossa are rare entities. Many surgical approaches to the clivus, the dorsum sellae, and the tip of the pyramid have been described. The transcondylar, subtemporal, transsphenoidal, and transoral avenues are suitable microsurgical approaches and are often combined with endoscopy. In the last few years, endoscopic skull base surgery came more and more into the focus. The endoscopic transsphenoidal approach was extended by bony resection of the clivus or the pyramid to reach 7 different pathologies of the ventral wall of the posterior fossa.

Method: A pure endoscopic transnasal navigated approach was used in 5 operations. Entities included 1 clivus chordoma, 1 chondrosarcoma,1 metastasis of the posterior clinoid process, 1 CSF fistula of the clival dura, 1 basilar impression of the dens, 1 cholesterol granuloma, and 1 Rathke cyst of the pyramid tip. The four-hand and two-nostril technique with a 4-mm, 0-degree endoscope was used. A thin sliced computer tomography served for neuronavigation, and registration was achieved with surface matching.

Results: Tumor reduction of 90% was achieved in the giant clivus chordoma and the chondrosarcoma, complete resection was attained of the metastasis and of the dens up to the base of C2 , the CSF fistula was sealed, the cholesterol granuloma was completely drained, and the Rathke cyst was completely resected. The aim of the procedure was reached in all cases. No transformation to microscopic technique or a second procedure via a different trajectory was necessary. No infection, bleeding, or new neurological deficits were encountered.

Discussion: The transnasal pure endoscopic approach is suitable for pathological processes of the ventral wall of the posterior fossa. In this small series, the complication rate was low with only minor side effects of the approach observed. Endoscopic transnasal skull base surgery should be considered as a technique to operate in the clivus, the ventral craniocervical junction, or the tip of the pyramid.