Cerebellar infarction secondary to os odontoideum.

A 43-year-old man developed cerebellar infarction due to atlantoaxial dislocation associated with os odontoideum. Cervical X-ray films confirmed os odontoideum, and conventional angiography revealed irregular narrowing of the right vertebral artery at the axis level. A correlation between the vertebral artery lesion and atlantoaxial instability was shown with 3-dimensional (3-D) computed tomographic (CT) angiography. This is the first case of atlantoaxial dislocation with vertebral artery stenosis demonstrated 3-D CT angiography. 3-D CT angiography can support the conventional angiography with respect to the diagnosis and management of vertebral artery insufficiency associated with occipitocervical deformity.