ATP1A3 and alternating hemiplegia of childhood: Mutations in ATP1A3 gene are responsible for a continuum spectrum of disorders encompassing different entities, such as early-infantile epileptic encephalopathy (EIEE), AHC, cerebellar ataxia with pes cavus, optic neuropathy and sensorineural hearing loss (CAPOS), recurrent encephalopathy with cerebellar ataxia (RECA), and rapid-onset dystonia-parkisonism (RDP) [107,217,218,219].