Alternating hemiplegia of childhood is a rare syndrome of episodic hemi- or quadriplegia lasting minutes to days. Most cases are accompanied by dystonic posturing, choreoathetoid movements, nystagmus, other ocular motor abnormalities, autonomic disturbances, and progressive cognitive impairment. Alternating hemiplegia of childhood-1 (AHC1) is caused by heterozygous mutation in the ATP1A2 gene on chromosome 1q23. (OMIM)