Intradural Synovial Cyst of the Upper Cervical Spine: A Rare Cause of Symptomatic Cord Compression

Background: Synovial cysts are commonly observed soft-tissue masses of the spine, typically extradural and located in the lumbar region. We describe a very rare symptomatic case of a C1-C2 intradural synovial cyst.

Case Description: A 78-year-old female presented with progressive left side weakness, paresthesia, and hyperreflexia. The magnetic resonance imaging revealed a well-circumscribed, subtly enhancing lesion medial to the C1-2 facet, causing cord compression and edema. Using neurophysiological monitoring, surgery included a modified laminectomy of C2 with the removal of the C1 posterior arch. When the dura was opened, a sizable intradural extramedullary lesion was encountered, the cyst was successfully drained and partially resected. The histopathological diagnosis was consistent with a synovial cyst. Postoperatively, the patient's strength on the left side improved gradually until she was fully ambulatory. Postoperative imaging showed no recurrence at 8 months follow-up.

Conclusion: Synovial cysts should be considered among the differential diagnose of C1-2 cysts. They can occur intradurally and compress the spinal cord resulting in a significant neurological deficit. Cyst excision may be accomplished utilizing a limited laminectomy for cyst identification and drainage, accompanied by partial resection of the cyst wall. Such intervention can lead to good clinical outcomes.