Nine patients with an AHC phenotype did not have a mutation in ATP1A3 on direct gene sequencing, but the majority (6 of 9, 67%) had the same dynamic cardiac electrical abnormalities observed in the ATP1A3 mutation carriers, with 1 patient even requiring the insertion of a pacemaker due to symptomatic conduction disease. Here, ATP1A3 is linked to alternating hemiplegia of childhood.