Pediatric atlantoaxial instability presenting as cerebral and cerebellar infarcts.

Atlantoaxial instability can lead to severe, permanent neurologic compromise and death if not treated by cervical fusion. However, identification of atlantoaxial subluxation can be difficult owing to the often confusing signs and symptoms. We describe a patient with unexplained transient repeated cerebral and cerebellar signs who had 10 mm of translation of the atlas on the axis owing to os odontoideum with infarcts in the cerebellum and occipital parietal lobes. These correlated with angiographically documented vertebral artery narrowing at the level of the axis and the subsequent low flow to the posterior cerebellum. After stabilization and fusion of the cervical spine, the patient regained normal neurologic function and has remained symptom-free at 2 years of follow-up.