Abstract
BACKGROUND: Retro-odontoid pseudotumors are soft tissue lesions behind the odontoid process, commonly associated with chronic atlantoaxial instability from rheumatoid arthritis, Down syndrome, and untreated injuries. Surgical techniques have evolved to address these histologically benign lesions when their mass effect causes cervical myelopathy. Historically, these were treated by direct spinal cord decompression via a transoral odontoidectomy. It is now understood that most retro-odontoid pseudotumors will regress with atlantoaxial fixation and fusion. Although uncommon, cystic masses can be associated with retro-odontoid pseudotumors and can create a secondary space-occupying lesion contributing to further cord compromise. Such cysts have been described in the extradural compartment. More uncommonly, they can erode through the ventral dura mater. OBSERVATIONS: A 63-year-old female with prior C4-7 anterior cervical discectomy and fusion presented with worsening gait instability and myelopathy. MRI confirmed a retro-odontoid pannus with an adjacent left-sided cyst causing severe spinal cord compression. Intraoperatively, the cyst was discovered to be extradural and adhered to the ventral dura, prompting a transdural approach for resection. LESSONS: A paucity of literature exists regarding the management of symptomatic retro-odontoid cysts. This report demonstrates key steps of a transdural approach for the resection of a large retro-odontoid cyst with strong adherence to the ventral dura, accompanied by an intraoperative video and graphical illustrations. https://thejns.org/doi/10.3171/CASE25757.