Alternating hemiplegia of Childhood is a condition that causes transient weakness of either, or both, sides of the body. The attacks may alternate or sometimes overlap, that is the second side is affected before the first recovers. Attacks start in the first eighteen months of life but the earliest episodes are often unusual irregular eye movements. 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.
What causes it?
Scientists discovered in 2012 that, in 75% of those affected, AHC is caused by specific mutations in the gene ATP1A3. (See “Cause of AHC identified” section). Affected children usually have significant learning disabilities and motor organisational problems, including unsteadiness. Although there is a concern that these problems may increase with repeated episodes, the available evidence does not support this.
All children and young adults are different and have different triggers. Some common ones are as follows:
- Water – bathing and swimming.
- Changes/extremes of temperature.
- Bright lights and loud noises.
- Fluorescent lights/Low energy bulbs
- Strong odours(Perfumes etc)
- Childhood illnesses and infections.
- Tiredness and lack of sleep.
What’s the treatment
The treatment most commonly used is flunarizine (a calcium channel blocker). Other drugs have not been found to be consistently helpful. Management is complex because of the multiple impairments and episodic deterioration. Bilateral attacks (those that occur on both sides of the body) may pose hazards for nutrition, hydration and breathing.
As each child is so different with this condition a treatment or medication that works for one will not necessarily work for another.
From a parents point of view other drugs that have been beneficial on individuals include topamax, epanutin, pitzotifin.
Various other anti-convulsant drugs are used and anti-migraine drugs have been tried.
Cause of AHC identified
Cause of Alternating Hemiplegia identified
An international consortium of scientists, led jointly by researchers at UCL’s Institute of Neurology and Duke University, USA, has identified the specific genetic mutation that causes Alternating Hemiplegia, a rare neurological condition affecting an estimated one child in every million. Using the newest genetic technology, next-generation sequencing, the study published in Nature Genetics, showed that de novo mutations in the gene ATP1A3 cause the condition (de novo mutations are genetic mutations not present in the parents’ genes). This particular genetic mutation is present in 75% of those affected by AHC.
Alternating Hemiplegia is characterised by onset in infancy or childhood of episodes of weakness of one side of the body; later in the course of the disease, both sides may be affected at the same time. The weakness typically gets better, but reoccurs in the next episode. The symptoms can vary from child to child and from day to day. For many affected individuals, other symptoms also occur, including speech, swallowing, and behavioural problems. Intellectual difficulties, movement disorders and epilepsy can also occur. The variety of symptoms and signs, and their variation over time, can lead to delays in diagnosis, multiple tests and investigations, and sometimes use of inappropriate treatments. So far, no definitive diagnostic test has been available, and a rational understanding of the disease has not been possible.
This study paves the way for future rational treatments for the condition, through a better understanding of underlying disease mechanisms. Whilst this will take some time, the discovery will have a direct impact in enabling more rapid, specific diagnosis of the condition, preventing unnecessary tests and misdirected treatment.
Jill Bailey, from the UK Alternating Hemiplegia Support Group said: “The discovery of the gene has given hope to parents whose lives are dominated by alternating hemiplegia. Our hope is that in the future a drug will be found that stops our children suffering these awful hemiplegic attacks. Our hope is that more money will be available for further research. Our hope is that our children will have a better life.”
The research was jointly led by Professor Sanjay Sisodiya at UCL and Professors David Goldstein and Mohamed Mikati at Duke University, and is published in Nature Genetics. The study was funded by several sources; Professor Sisodiya’s funding was from The Wellcome Trust.