Symptomatic cervical synovial cyst associated with an os odontoideum diagnosed by magnetic resonance imaging: case report and review of the literature.

STUDY DESIGN: The first case of a synovial cyst of the upper cervical spine associated with os odontoideum diagnosed by magnetic resonance imaging is presented.

OBJECTIVES: To evaluate distinct magnetic resonance imaging findings of a cervical synovial cyst located anterior to the cord and discuss its association with os odontoideum. These findings may guide further investigations.

BACKGROUND: Synovial cysts of the spine are uncommon findings. They occur mostly dorsolaterally and with greatest frequency in the lumbar spine and are rarely symptomatic. No association with os odontoideum has been reported before.

METHODS: A single subject with symptoms of deterioration in his hand functions was examined by a 2. 0-T magnetic resonance imager.

RESULTS: Magnetic resonance imaging of the cervical spine showed an os odontoideum connected to the body of C2 by a synovial joint that had a cystic extension posteriorly compressing the cord.

CONCLUSION: Synovial cysts should be considered in the differential diagnosis of an extradural mass of the upper cervical spine. Magnetic resonance imaging should be the choice in the investigation of such cases.