Alternating hemiplegia of childhood

Alternating hemiplegia of childhood (AHC) is a rare genetic disease which causes intermittent paralysis and progressive mental retardation starting in childhood.

Symptoms
AHC usually occurs before four years of age and can present in either a severe or a less severe form.


 * The less severe form has a good prognosis and is indicated by episodes occurring primarily at night, and can often be related to migraines. There is no neurological impairment in this form of AH.


 * The severe form is indicated by the usual paralysis, mental impairment, gait and balance impairment, excessive sweating, and changes in body temperature. Seizures and movement disorders can also be present.

Etiology
Some cases of AHC are thought to be the result of a channelopathy - the gene (an isoform of the sodium-potassium ATPase) has been implicated in at least one family. There is overlap with the syndrome of familial hemiplegic migraine in which the ATP1A2 gene undergoes a different mutation.

Treatment
Drug therapy includes flunarizine, a calcium channel blocker. It may help to reduce the severity and duration of attacks of paralysis associated with the more serious form of alternating hemiplegia.

Prognosis
Children with the benign form of alternating hemiplegia have a good prognosis. However, those who experience the more severe form have a poor prognosis because intellectual and mental capacity do not respond to drug therapy, and balance and gait problems continue. Over time, walking unassisted becomes difficult or impossible.