Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a disease that affects a child’s nervous system. It damages the nerve cells that control how muscles work. As a result, a child’s muscles slowly weaken and waste away.

SMA is a genetic disease. A child can get it only if he or she inherits the gene for it from both parents.

Types of spinal muscular atrophy

SMA has several types. Three of them affect children. Each has different symptoms. And each starts at a different age.

  • Type 1. This is known as Werdnig-Hoffman SMA. It’s also called infantile-onset SMA. A child with this type often has symptoms just after birth. An infant may have trouble moving, swallowing, and feeding. The infant may not be able to hold up his or her head. A child with this severe form of SMA usually dies within 2 to 6 years. Children with type 1 often die from breathing problems.

  • Type 2. This is called juvenile or chronic SMA. A child with this type is often diagnosed at age 6 to 18 months. The main symptom is muscle weakness all over the body. This causes trouble walking and standing. Children with type 2 may need help moving around. They may need a walker or wheelchair. They often live into adulthood. But they are more prone to respiratory infections.

  • Type 3. This is the mildest form. It can affect children from 18 months old up to their teen years. The most common symptoms include clumsiness, trouble walking and climbing steps, fine tremor, and muscle weakness. Children with type 3 often have trouble getting up from a sitting position.

Diagnosing spinal muscular atrophy

SMA is diagnosed after symptoms start and after testing is done. For instance, early signs of muscle weakness may point to the disease. Your child’s healthcare provider will also do a physical exam and ask about your child’s health history.

Other tests can confirm SMA. These include:

  • Blood tests. These check for the gene that causes SMA.

  • Muscle biopsy. The healthcare provider takes a sample of muscle tissue to look at under a microscope.

  • Electromyogram. This test can find electrical problems in the muscles.

Treating spinal muscular atrophy

Nusinersen is the first medicine approved to treat children and adults with SMA. Nusinersen is injected by spinal tap (lumbar puncture) around the spinal cord.

SMA can’t be cured. So finding it early is important. Treatment may depend on your child’s age, his or her overall health, and the type of SMA he or she has.

Children with SMA may have problems breathing and swallowing. This is because the disease affects the muscles that control these functions. Children with severe cases are especially at risk for these problems. They may need a breathing machine or nutritional care.

Weak arm and leg muscles can make it hard for a child to walk and stand. A wheelchair or walker can help keep a child independent. Physical therapy and exercise can help, too. They can make it easier to move and stay flexible.

Many children with SMA also have scoliosis. Scoliosis is a condition that causes the spine to curve. A healthcare provider may recommend special devices to help prevent this problem. Surgery may be needed to fix it.

Online Medical Reviewer: Hanrahan, John, MD
Online Medical Reviewer: Kolbus, Karin, RN, DNP, COHN-S
Date Last Reviewed: 2/1/2018
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