Endoscopic endonasal approach to the ventral cranio-cervical junction: Anatomical study

Objective. In order to develop an endoscopic endonasal approach to the ventral cranio-cervical junction and odontoid process under the concept of a minimally invasive surgical strategy, a cadaver study was performed. Methods. Sixteen artery-injected adult head specimens were used. Endonasal endoscopic approach was made through one- or two-nostril routes following the Jho's endonasal paraseptal technique. Rod-lens endoscopes, which were 2.7 or 4 min in diameter, 18 cm in length with 0-, 30-, and 70-degree lenses, were used. Results. Surgical landmarks leading to the craniocervical junction were the inferior margin of the middle turbinate, nasopharynx and Eustachian tube. The nasopharynx was readily identified following the inferior margin of the middle turbinate. The line drawn between the Eustachian tubes indicated the juncture between the clivus and atlas. With a midline mucosal incision, the ventral cranio-cervical junction was exposed. Odontoid resection was performed with removal of the anterior arch of the atlas. Clival resection can be performed as much rostral as required. Manoeuverability of the surgical instruments was better with a two-nostril technique than with a one-nostril. Although the entire midline clivus was accessible rostrally, C-2 was the caudal limit through this endonasal route. A suturing device needed to be developed for mucosal or dural closure for live operations, Conclusion. This cadaver study demonstrates that an endoscopic endonasal approach to the ventral cranio-cervical junction and odontoid process can be a valid alternative to the conventional transoral approach.