Alternating hemiplegia of childhood (AHC) is a rare neurological disorder in which repeated, transient attacks of hemiplegia occur and may alternate from one side of the body to the other. The attacks may last for minutes, hours or even days and are normally relieved by sleep. High stress activities have been know to cause attacks as well as the presence of a cold or upper respiratory problems. Children are affected by bright lights, wind, temperature changes and exposure to water. Many attacks occur for no apparent reason. The disease is not fatal nor known to shorten life expectancy. Its cause(s) is unknown and there is no known cure.
Despite the reference to childhood in the name, there is no evidence to suggest that a child will be cured simply as they age. Many children exhibit a greater degree of ability to handle the attacks or even avoid factors that cause the attacks as they age, but this is not always the case. AHC would still be considered a "new" disorder due to its relatively recent diagnosis. There is developing evidence that AHC may cause ongoing mental and neurological deficits with a progressive course.
The number of known children diagnosed with AHC in the United States is less than 100 and worldwide it may be less than 250. Due to misdiagnosis it is difficult to determine how many children actually have AHC.