Alternating hemiplegia is a rare childhood neurological disorder that is characterized by recurrent episodes of paralysis that involve one or both sides of the body, multiple limbs, or a single limb.
The paralysis may affect different parts of the body at different times and may be brief or last for several days. Oftentimes these episodes will resolve after sleep. Affected children may also have abnormal movements involving stiffening or "dance-like" movements of a limb, as well as walking and balance problems. Some children have seizures.
Alternating hemiplegia is extremely rare – approximately 1 in 1,000,000 people have this disorder. It develops in childhood, most often before the child is 18 months old. Most children do not have a family history of the disorder; however, recent studies have show that some children with a family history have mutations in the ATP1A2 gene. Mutations in this gene have previously been associated with families affect by familial hemiplegic migraine.
Children may have normal or delayed development. There are both benign and more serious forms of the disorder. Children with the benign form of alternating hemiplegia have a good prognosis. Those who experience the more severe form have a poor prognosis because intellectual and mental capacities do not respond to drug therapy, and balance and gait problems continue. Over time, walking unassisted becomes difficult or impossible.
Hemiplegic attacks can be brought on by particular triggers, and management of alternating hemiplegia often centers around avoiding common or known triggers. While triggers vary greatly from person to person, there are also some common ones which are prevalent in many patients. Common triggers include:
While avoiding triggers may help, it cannot prevent all hemiplegic episodes because many occur without being triggered. Because attacks and other associated symptoms end with sleep, various sedatives can be used to help patients sleep.
Drug therapy including flunarizine may help to reduce the severity and duration of attacks of paralysis associated with the more serious form of alternating hemiplegia.