Spinal Muscular Atrophy

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Spinal muscular atrophy (SMA) is a genetic disease that affects the spinal cord and nerves, resulting in muscle wasting and weakness.

It is an autosomal recessive disease. This means that both males and females are equally affected, and that two copies of the gene, one inherited from each parent, are necessary to have the condition. When both parents are carriers, there is a one in four, or 25 percent, chance, with each pregnancy, to have a child with SMA.

What are the symptoms of spinal muscular atrophy?

Spinal muscular atrophy is sometimes difficult to diagnose, as symptoms can resemble other conditions or medical problems. Each child may experience symptoms differently. There are four types of spinal muscular atrophy based on symptoms and age of onset. The child may have the following symptoms:

  • Type I (also called Werdnig-Hoffman or infantile-onset SMA). This is the most severe type of SMA and may be present at birth. Infants have problems holding their head, sucking, feeding, swallowing and typically move very little. The muscles of the chest are also affected. The motion of the tongue is described as having “worm-like” movements. Many children will not survive past the age of two to six years because of breathing problems.
  • Type II (juvenile SMA, intermediate SMA or chronic SMA). This form of SMA is seen in children from six months to 18 months of age. They typically have generalized muscle weakness and may require braces, walkers or a wheelchair for assistance. Life expectancy may extend to the 20s and 30s.
  • Type III (also called Wohlfart-Kugelberg-Welander or mild SMA). This form of SMA affects children older than 18 months of age or as late as adolescence. These children show signs of clumsiness, difficulty walking, mild muscle weakness and may be developmentally delayed. These children live long into their adult years.
  • Type IV. This form of SMA affects adults in their 30s and 40s, resulting in a walking disability.

How is spinal muscular atrophy diagnosed?

Diagnostic tests that may be performed to confirm the diagnosis of spinal muscular atrophy include the following:

  • Blood tests
  • Muscle biopsy
  • Genetic tests
  • Electromyogram (EMG).

How is spinal muscular atrophy treated?

There is no cure for spinal muscular atrophy. The key to medically managing spinal muscular atrophy is through early detection.

The goal of treatment is to prevent respiratory problems and provide adequate nutritional care to the child since the swallowing and breathing muscles can be affected by this condition.

The extent of the problem is dependent on the severity of the condition and the presence of other problems that could affect the child. In severe cases, a breathing machine may be required to help the child breathe easier.

The health care team educates the family after hospitalization on how to best care for their child at home and outlines specific clinical problems that require immediate medical attention by his or her doctor. A child with spinal muscular atrophy requires frequent medical evaluations throughout his or her lifespan.