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.