What is Alternating Hemiplegia of Childhood (AHC)
Alternating hemiplegia of childhood is a rare nervous system disorder. It causes abnormal movements, weakness, or complete loss of movement.
What are the causes?
Most of the time, AHC is caused by a genetic defect (mutation) in the ATP1A3 gene. This gene makes a protein that is needed for normal nerve and brain function. This mutation usually happens for the first time during conception (de novo mutation). It is not one that is passed down through families.
In some children, other genes may be involved in AHC. Some of these genes may be passed down through families (hereditary).
Sometimes, no cause can be found.
In some children, certain activities or exposures can trigger signs and symptoms of AHC. These may vary from child to child. Attacks may also occur without triggers. Common triggers include:
- Extreme heat or cold.
- Loud noises.
- Changes in sleep.
- Strong smells.
- Bathing or swimming.
- Bright lights.
- Certain foods.
- Stress.
- Fear.
What increases the risk?
In very few cases, a gene that causes AHC can be passed down through families. There are no other known risk factors for AHC.
What are the signs or symptoms?
Symptoms usually start by the time a child is 18 months old.
Symptoms can range from mild to severe and can happen on one or both sides of the body. The affected side may switch. However, complete loss of movement usually occurs on one side of the body (hemiplegia). Attacks of AHC may come and go. They also may change. Signs and symptoms may occur every day or only every few weeks or months. They may last minutes, hours, or days. Sleep often relieves an attack of AHC. In some children, symptoms get worse and more frequent over time.
Eyes that jerk or drift out of position may be one of the first signs of AHC. Other signs and symptoms include:
- Other abnormal eye movements.
- Weakness.
- Loss of the ability to move (paralysis).
- Numbness.
- Uncontrolled movements.
- Clumsiness.
- Poor balance.
- Unusual and painful body positions.
- Changes in behavior.
- Learning problems and developmental delays.
- Loss of learned skills.
- Changes in body temperature.
- Shortness of breath or wheezing during an attack.
- Seizures.
How is this diagnosed?
Your child’s health care provider may diagnose AHC based on the signs and symptoms that your child develops over time. These are similar to the signs and symptoms of many other nervous system conditions of childhood. Your child may need many tests to rule out other conditions before getting a diagnosis of AHC. These may include:
- MRI of the brain.
- Blood tests.
- Cerebrospinal fluid test.
- Electroencephalogram (EEG) to measure the electrical activity in the brain.
If these tests do not show another cause for the symptoms, your child may have a blood test to look for the ATP1A3 gene.
How is this treated?
There is no cure for AHC. However, some treatments can prevent and manage attacks. You may work with a team of medical specialists to come up with the best care plan for your child. Help from special education therapists, physical therapists, nutrition experts, and mental health professionals can improve your child’s quality of life. Your child may also need to take medicines, such as:
- Calcium channel blockers to make attacks occur less often.
- Sedatives to end an attack.
- Antiseizure medicines to prevent seizures.
Follow these instructions at home:
- Learn as much as you can about your child’s condition.
- Learn what triggers may cause your child’s attacks. Avoid these if possible.
- Work closely with your child’s team of health care providers.
- Give medicines only as directed by your child’s health care provider.
- Keep all follow-up visits as directed by your child’s health care provider. This is important.
Contact a health care provider if:
- Your child has new symptoms.
- Your child’s symptoms last longer or become more frequent.
Get help right away if:
- Your child has a seizure.
- Your child has trouble breathing.
