Chiari I malformation with syrinx.

The Chiari I congenital malformation is characterized by caudal displacement of the cerebellar tonsils through the cervical canal. Although this malformation is often asymptomatic, coexisting syringomyelia can result in neurologic symptoms. We report a case of progressive ataxia with brainstem dysfunction in an adolescent female manifesting a severe Chiari I malformation with syrinx. Chiari decompression 4 years after initial presentation led to rapid improvement in most of her long-term symptoms. This case demonstrates the importance of consideration of Chiari I with syringomyelia in the differential diagnosis of progressive ataxia and brainstem symptoms.