Tomokazu Ito, Masahiro Hayashi and Toshihiko Ogino
Department of Orthopaedic Surgery, Yamagata University School of Medicine, Yamagata City, Japan

Synovial cysts of the cervical spine are extremely rare. We describe an 8-year-old boy with atlantoaxial subluxation and hypoplasia of the dens. Magnetic resonance imaging showed a round lesion, posterior to the odontoid process. This mass was characterized by a low signal intensity on T1-weighted images, and high signal intensity on T2-weighted images. The retrodental synovial cyst disappeared after posterior atlantoaxial arthrodesis.

Key words: synovial cyst; cervical spine; MRI; transarticular screw fixation