Bipartite Atlas With Os Odontoideum and Synovial Cyst Case Report and Review Literature

Study Design. Case report and review of the literature. Objective. To present an os odontoideum with bipartite atlas and synovial cyst at the C1-C2 junction in a 13-year-old girl and to review the relevant background literature. Summary of Background Data. Bipartite atlas associated with os odontoideum and synovial cyst at the C1-C2 junction is extremely rare. Methods. The patient's clinical presentation, evolution of physical findings, and sequential radiologic studies. Surgery of the bipartite atlas with os odontoideum and synovial cyst. Posterior fixation between occipital and C 2 without resection of the mass was performed. Results. The patient had significant improvement and spontaneous regression of the cyst was identified on the follow-up magnetic resonance imaging (MRI) taken 3 months after posterior fixation. To our knowledge, no case of a bipartite atlas with os odontoideum and synovial cyst with complete recovery of an accompanying quadriparesis after reduction has been previously reported in English medical literature. Conclusion. We described a rare association of an anterior arch defect, posterior arch aplasia, os odontoideum, and synovial cyst at the C1-C2 junction. This case report supports surgical intervention of synovial cyst with craniovertebral instability using posterior fixation without resection of the cyst.