Resolution of cystic deterioration of the C1-2 articulation with posterior fusion: Treatment implications for asymptomatic patients

Background: The authors previously reported anterior decompression of C1-2 synovial cysts and subsequent posterior fusion in a large series. Although the surgical morbidity and mortality were acceptable, prior reports of stand-alone C1-2 fusion with resolution of cyst compression presumptively by correction of joint instability were intriguing and did not involve the morbidity associated with the transoral procedure. Methods: Three cases of retroodontoid cysts that resolved after posterior instrumentation and fusion are presented. These cysts were not associated with rheumatoid arthritis. An additional nine cases from the literature in which fusion was performed without cyst extirpation are reviewed. Results: Three patients presented with retroodontoid cysts. Two patients underwent posterior occipitocervical fusion with instrumentation alone. One patient underwent transoral decompression followed by occipitocervical fusion with instrumentation. In this one patient, magnetic resonance imaging performed early after the transoral procedure demonstrated substantial residual cyst. In all cases, follow-up magnetic resonance imaging performed 6-19 months later demonstrated near-complete resolution of the cysts. A literature review was done to find all other similar cases. Demographics, clinical presentation, imaging, and surgical outcome of these cases were analyzed. Conclusions: In asymptomatic patients with a synovial cyst of the atlantoaxial junction, posterior fusion alone may lead to complete resolution of the cyst; however, in neurologically symptomatic patients with similar lesions, cyst decompression coupled with posterior fusion is recommended to ensure the highest chance of cyst resolution and clinical improvement.