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Alternating Hemiplegia of Childhood (AHC)

What is Alternating Hemiplegia (AHC)?

Alternating Hemiplegia of Childhood is a rare neurological disorder that develops in childhood, most often before the child is 18-months old.

The disorder is characterized by recurrent episodes of paralysis that involve one or both sides of the body, multiple limbs, or a single limb. The paralysis may affect different parts of the body at different times and may be brief or last for several days. Oftentimes these episodes will resolve after sleep. 

There are both benign and more serious forms of the disorder.

What are the symptoms of Alternating Hemiplegia of Childhood (AHC)?

Children with alternating hemiplegia exhibit a wide range of symptoms. These include:

  • Tonic attacks (lack of muscle tone)
  • Dystonic posturing (stiffening of extremities)
  • Ataxia (lack of coordination when performing voluntary movements)
  • Nystagmus (fast uncontrollable movements of the eyes that may be side to side, up and down, or rotary)
  • Ocular motor abnormalities (eye disorders)
  • Developmental delays
  • Seizures 

Up to 50% of children with AHC develop “true seizures” sometime during the course of their illness.

What causes Alternating Hemiplegia of Childhood (AHC)?

In at least 2/3 of individuals, alternating hemiplegia is caused by a mutation in the ATP1A3 gene.

In rare cases where alternating hemiplegia runs in families, it is thought that the disorder is inherited as an autosomal dominant trait. 

How is Alternating Hemiplegia of Childhood (AHC) diagnosed?

A diagnosis is based upon identification of characteristic symptoms, a detailed patient history, a thorough clinical evaluation and a variety of specialized tests.

The specific diagnostic criteria are: 

  • Onset of symptoms before 18 months
  • Repeated episodes of hemiplegia that sometimes involve both sides of the body
  • Quadriplegia that occurs as an isolated incident or as part of a hemiplegic attack
  • Relief from symptoms upon sleeping
  • Additional paroxysmal attacks such as dystonia, tonic episodes, abnormal eye movements or autonomic dysfunction
  • Evidence of developmental delay or neurological abnormalities such as choreoathetosis, ataxia or cognitive disability
  • Cannot be attributed to another cause

What are the treatments for Alternating Hemiplegia of Childhood (AHC)?

Drug therapy including verapamil may help to reduce the severity and duration of attacks of paralysis associated with the more serious form of alternating hemiplegia

Where can I find out more about Alternating Hemiplegia of Childhood (AHC)?

Alternating Hemiplegia Articles