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.
Some cases of AHC are thought to be the result of a channelopathy - the gene ATP1A2 (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.
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.
Referencesnl:Alternating Hemiplegia of Childhood
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