Introduction: Originally decribed as 'Alternating Hemiplegia of Childhood' (AHC), ongoing observation of some children extends into young adulthood.

Methods: Observational longitudinal studies in a small cohort of AHC include phenotype, genotype, EEG and sleep, drug therapy and long-term follow-up. Variablity was noted in age of onset, phenotypic expression, seizure activity, EEG changes especially in sleep, and early response to medications: gamma-hyodroxy butyrate, topiramate, phenytoin, flunarizine and ASA.

Results: In three cases, one had onset in infancy, two in childhood now young adults, still with acute hemiplegic episodes, two continued to have partial-onset seizures requiring AED therapy with reasonable control. All had comorbidities: learning disorder, speech or memory deficits, and spasticity. EEG studies were variable and changed with cerebral development, not specific to AHC. Two had the known genotype. To date the prognosis has been guarded for long-term outcome and quality of life measures are needed.

Conclusion: Although the genotype is known, phenotypic variablity, EEG evolution and response to therapy showed variability into adulthood. A name change may be needed and transition to adult neurology optimised.