Radiology Resident Case of the Week

Os Odontoideum

September 26, 1996

Clinical Sx:
Local neck pain, stiffness or spasm, upper or lower extremity weakness, episodes of paresis or paresthesias, headaches, torticollis, or gait disturbances.

Etiology/Pathophysiology
Unknown. Some evidence suggests that this is an aquired problem secondary to trauma.

Pathology:
Complete separation from the axis of a malformed small odontoid which allows hypermobility at C1-C2. The odontoid remnant may even be fused with the clivus.

Miscellaneous
Hypertrophic changes involve the normal location of the anterior C1 arch.

Imaging

DDX
Split atlas secondary to anterior and posterior arch rachischisis.

Key references
Diagnosis of Bone and Joint Disorders. Resnick and Niwayama, 2nd ed. 1988.

Essentials of Neuroimaging. Kirkwood. Churchill Livingstone. 1990.

Radiology Review Manual. Dahnert. 1996.

ACR Code

Keywords:

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Last Modified: April 24, 1997