A1.6.5 Alternating hemiplegia of childhood

Infantile attacks of hemiplegia involving each side alternately, associated with a progressive encephalopathy, other paroxysmal phenomena and mental impairment.

Diagnostic criteria:
A. Recurrent attacks of hemiplegia alternating between the two sides of the body and fulfilling criteria B and C
B. Onset before the age of 18 months
C. At least one other paroxysmal phenomenon is associated with the bouts of hemiplegia or occurs independently, such as tonic spells, dystonic posturing, choreoathetoid movements, nystagmus or other ocular motor abnormalities and/or autonomic disturbances
D. Evidence of mental and/or neurological deficit(s)
E. Not attributed to another disorder.

This is a heterogeneous neurodegenerative disorder. A relationship with migraine is suggested on clinical grounds. The possibility that it is an unusual form of epilepsy cannot be ruled out. Mutations in the ATP1A3 gene (encoding the sodium-potassium [Na+/K+] ATPase α3 subunit) are likely to be responsible for at least 70% of cases.