AHC has an onset in early childhood and is associated with several severe symptoms including episodes of one-sided weakness or paralysis, dystonia, intermittent abnormal eye movements and seizures.16,17 RDP often has an abrupt onset of dystonia triggered by a physical or psychological stressor.18,19 In milder cases, symptoms may be restricted to the limbs,20 suggesting that ATP1A3 mutations may cause pathophysiology of spinal motor networks, including lower motor neurons innervating the limbs. Here, ATP1A3 is linked to alternating hemiplegia of childhood.