Observe Alternating Hemiplegia of Childhood (OBSERV-AHC) Study

Inclusion Criteria: \- Patients who fit the Aicardi Alternating Hemiplegia of Childhood clinical criteria of any age. The Aicardi Criteria are six : * Paroxysmal hemiplegia episodes. * Bilateral hemiplegia or quadriplegia episodes. * Other paroxysmal manifestations, such as abnormal eye movements, nystagmus, strabismus, ataxia, dystonia, choreoathetosis, tonic spells, or autonomic disturbances. * Evidence of permanent neurological dysfunction, which can manifest as cognitive impairment, developmental delay, and/or persistent motor deficits such as spastic diplegia/quadriplegia, hypotonia, ataxia, choreoathetosis, or dystonia. * Sleep relieves symptoms, although attacks may resume soon after awakening. * First signs of dysfunction occur prior to the age of 18 months. Exclusion Criteria: * Patients who do not have a mutation of the ATP1A3 gene and having only some of the above criteria * Patients and / or their parents / legal guardian having provided their opposition to the study. * Incapacity of patient / parent or other referent adult to participate in the prospective phase of observation of different paroxysmal events of the disease and in the scoring of the Vineland II adaptive behavior scales. * Diagnosis of another disease, which could explain the presence of symptoms mentioned in the criteria of Aicardi.