What is Alternating Hemiplegia of Childhood (AHC)

What is AHC

What is Alternating Hemiplegia of Childhood (AHC)?

AHC is a rare neurological disorder in which repeated, transient attacks of hemiplegia occur, affecting one side of the body or the other, or both sides of the body. The hemiplegia (paralysis of a portion of the body) ranges from simple numbness in an extremity to full loss of feeling and movement. The attacks may last for minutes, hours or even days and are normally relieved by sleep. The attacks of hemiplegia may alternate from one side of the body to another.

What other symptoms are associated with AHC?

Children with AHC have exhibited a wide range of symptoms in addition to AHC. These include tonic attacks (lack of muscle tone), dystonic posturing (stiffening of extremities), nystagmus and other oculomotor abnormalities (eye disorders), developmental delays, mental retardation and seizures. Not all children suffer from all of these associated symptoms and there is no current evidence to prove that these symptoms are associated with, or caused by, AHC.

What causes a hemiplegic episode?

The causes of hemiplegic attacks differ among children. 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.

Will a child “grow out of” AHC?

Although the name AHC contains “of childhood” in it, 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.

What are the long term effects of AHC?

At this time, AHC would still be considered a “new” disorder due to its relatively recent diagnosis. There is no proof that the disease is fatal or shortens life expectancy is any way, but sufficient documentation is not available at this time. There is developing evidence that AHC may cause ongoing mental and neurological deficits with a progressive course.

What causes AHC and is there a cure?

A de novo mutation in ATP1A3 causes the episodes for 80% of the AHC individuals but other mutated genes cause the episodes for the remaining 20%. The Affected persons 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.

Are there any current treatments for AHC?

The drug Flunarizine (trade name Sibelium) has been used successfully in many cases to lessen the effects of AHC. Other drugs that induce sleep have also been used to reduce the severity and length of attacks. Because the effects of AHC are thought to be cumulative in relation to damage to the brain, reducing the severity of attacks may have significant positive long term benefits.

How is AHC diagnosed?

Many children are initially diagnosed with epilepsy or other seizure disorders and prescribed anticonvulsent medications. While some do suffer from seizures, the use of these drugs are generally unwarranted and produce no benefit. It is unknown how many children are currently misdiagnosed. To properly diagnose AHC, other similar disorders are ruled out. These include vascular disorders, migraines, cerebral emboli, blood dyscrasia, metabolic disorders (such as aminoacidopathies), and mitochondrial disorders (such as MELAS syndrome). Diagnosed can be confirmed by exome sequencing

What is AHC