Alternating hemiplegia causes short-term weakness of either, or both, sides of the body. The attacks may alternate or sometimes overlap, meaning the second side is affected before the first recovers. The attacks last from less than an hour, which is unusual, to several days. When the attacks are prolonged, the manifestations are not apparent during sleep or for the first fifteen to twenty minutes on waking when they then return. This is a very characteristic finding and when there are bilateral attacks this may allow feeding and drinking to occur in that short clear period after waking. The episodes of hemiplegia are not epileptic in nature but epileptic seizures also occur in about half of those affected and require separate anti-epileptic drug treatment (see entry Epilepsy).
Alternating Hemiplegia of Childhood
Also known as: Alternating Hemiplegia
Alternating Hemiplegia of Childhood (AHC) is a rare neurological condition causing weakness in one or both sides of the body. The condition usually starts in the first 18 months of life, and is often initially signified by episodes of irregular eye movements.
What are the symptoms?
What are the causes?
Alternating hemiplegia is now known to be caused by mutations in ATP1A3, which is one of the genes responsible for the structure of a membrane protein involved in maintaining cell function.
How is it diagnosed?
Clinical diagnosis is based upon display of symptoms in the first 18 months of life, though a range of tests and scans may also be carried out to rule out other conditions.
How is it treated?
The treatment most commonly used is flunarizine (a calcium channel blocker). Other drugs have not been found to be consistently helpful. Management can be complex due to the unpredictable timing of attacks, and bilateral attacks may pose additional hazards for nutrition, hydration and breathing.
Inheritance patterns and prenatal diagnosis
It is autosomally recessively inherited, meaning that a person must inherit two copies of the mutated gene, one copy from each parent, to be affected by the disorder. If a person inherits just one copy of a mutated gene and one normal copy then, in most cases, the person will not be affected by the condition but is a healthy 'carrier'
It can theoretically be found by appropriate gene testing following a first case in the family, although this has never been done, and second cases are extremely rare.