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.


Last updated October 2013 by Professor Brian Neville, Emeritus Professor of Paediatric Neurology, UCL Institute of Child Health and Great Ormond Street Hospital, London, UK.

What are the symptoms?

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).

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

Inheritance patterns
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’

Prenatal diagnosis
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.

Is there support?

Alternating Hemiplegia Support Group

Tel: 01344 560 226

The Group is a self help group, established in 1993. It provides a listening ear and holds an annual family meeting. The Group is in touch with 26 families.

Group details last updated March 2014.


HemiHelp is a membership organisation supporting children and young people with hemiplegia and their families.

From 1 April 2018, HemiHelps’ services are being provided by our team at Contact.

These services include:

For more information you can email

Group details updated April 2018.

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