Chiari I malformation: association with seizures and developmental disabilities.

Chiari I malformation, a congenital abnormality in which deformed cerebellar tonsils are displaced downward through the foramen magnum, commonly presents in patients with headache or symptoms of dysfunction of the cerebellum, brain stem, and cervical spinal cord. We report 11 children with Chiari I malformation who presented with seizures and developmental delay in motor or language function with or without autistic features. To our knowledge, an association between Chiari I malformation and seizures or neurodevelopmental deficits or both has not been previously reported. We believe that Chiari I malformation should not be considered an incidental finding in these patients, but may be a marker for subtle cerebral dysgenesis. Chiari I and II malformations may constitute a complex but continuous spectrum, related to the timing and severity of a shared underlying embryologic mechanism.