Endoscopic Endonasal Approach to the Upper Cervical Spine for Decompression of the Cervicomedullary Junction Following Occipitocervical Fusion.

Basilar invagination is defined as abnormal upward and/or posterior displacement of the odontoid leading to ventral compression of the cervicomedullary junction. This condition leads to lower cranial neuropathies, sensorimotor deficits, and myelopathy. These symptoms can persist even after posterior decompression, which is an indication for ventral decompression. Transoral approaches to the upper cervical spine carry significant morbidity, limiting their utility. The endonasal approach to the upper cervical spine presents an alternative for patients with amenable anatomy. In this report, we present a case of a patient with type 1 Chiari malformation with persistent symptoms despite adequate posterior decompression through suboccipital craniectomy and C1 laminectomy. A retroflexed odontoid and dorsal clival bone lip contributed to persistent cervicomedullary compression. To address this, we performed a 2-stage procedure: an occiput-to-C4 fusion followed by endoscopic endonasal approach for dorsal clivusectomy, C1 anterior arch resection, and odontoidectomy. In the associated video, Supplemental Digital Content 1 (https://links.lww.com/CLINSPINE/A52), we demonstrate the step-by-step approach for this anterior approach including positioning, dissection through the nasopharyngeal fascia, identification of bony landmarks using an intraoperative CT scanner with 3-dimensional navigation guidance, and drilling/bony decompression of the dorsal clivus, C1, and C2. We also discuss key pearls, pitfalls, and preoperative/postoperative considerations critical to successful outcomes.