Alternating hemiplegia of childhood (AHC) is a rare neurological disorder of uncertain etiology, though growing evidence strongly supports mutation of the ATP1A3 gene as the primary cause of this disease. AHC is named for the transient episodes, often referred to as attacks or episodes, of hemiplegia from which those with the disorder suffer. These hemiplegic attacks can cause anything from mild weakness to complete paralysis on one or both sides of the body, and they can vary greatly in duration. Attacks may also alternate from one side of the body to the other, or alternate between affecting one or both sides during a single attack. AHC is associated with many symptoms besides hemiplegia, and the majority of these become apparent in early infancy. AHC typically presents before the age of