We report a rare case of synovial cyst of the dens (odontoid process)
in a 61 year old women with no previous history of trauma. She had pro
gressive symptoms of 1 year's duration due to spinal cord compression.
Magnetic resonance imaging of cervical spine revealed a large mass po
sterior to the dens which was compressing the spinal cord near the cer
vicomedullary junction. This lesion was at first considered radiologic
ally to represent an exuberant pannus formation or a meningioma of the
foramen magnum, but subsequent surgical intervention and pathological
examination revealed that it was a synovial cyst. Similar cases repor
ted in the literature are reviewed and discussed.