Atlantoaxial Synovial Cyst: Case Report and Literature Review

Degenerative cystic lesions of atlantoaxial joints are rare and generally believed to be due to mechanical instability. There is currently no consensus on the management of such lesions in symptomatic and asymptomatic patients. Both conservative and surgical strategies have been described. Surgery may involve anterior or posterior approaches with and without decompression and instrumentation.

We present a case report of a 45-year-old man who presented with new onset weakness and ataxia. Physical examination revealed decreased motor function in all extremities as well as positive Hoffman sign and ankle clonus bilaterally. An MRI of cervical spine showed a large atlantoaxial, T-2 hyperintense cystic lesion with cord compression and cord signal changes.

A C1 partial laminectomy was performed with resection of the cyst and C1-2 instrument fusion. Intra-operatively, the cystic lesion was found to be anatomically connected to the right C1-2 atlantoaxial joint with pathology showing fibroconnective tissue and chronic inflammatory changes. Post-operatively there were no complications and the patient was discharged to a rehabilitation facility. The patient was regaining gait and hand function by 3 months after surgery.

Atlantoaxial synovial cysts are rare and the optimal surgical approach has not been determined. We further conducted a literature review and found a total of 70 other cases of atlantoaxial synovial cysts reported to date in the literature. We attempt to analyze available data and evaluate anterior versus posterior approaches and the need for decompression, amount of cyst resection, and instrumentation.