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Spinal Muscular Atrophy


​​Spinal muscular atrophy, also known as SMA, is a condition affecting the spinal cord that causes progressive muscle weakness and atrophy. (Atrophy is the shrinkage of muscle.) SMA is a genetic condition and typically becomes evident during infancy.

As of 2021, Nebraska Legislature passed a bill that added newborn screening for muscular atrophy. Early intervention provides the best opportunity for treatment and to change the natural course of SMA.

Types of Spinal Muscular Atrophy

There are four types of spinal muscular atrophy, but only three affect children. They are categorized based on the age symptoms begin and severity of the symptoms.

  • Type 1 starts showing around 3 months of age but affects infants from birth until 6 months of age. This type is the most severe.
  • Type 2 begins showing symptoms between 7 and 18 months of age. This type is moderate to severe.
  • Type 3 is known as juvenile SMA and starts showing anywhere from 18 months of age to adolescents. This type is the mildest.

Causes of Spinal Muscular Atrophy

Spinal muscular atrophy is typically caused by complications with the SMN1 (survival motor neuron 1) gene. This gene is passed on from one or both parents. If a child has SMA, the gene was passed on by both parents. The SMN1 gene can also be passed on by one parent, but the child with more than likely not show signs of SMA. Genetic testing can be done to determine how likely it is a child will have SMA.

Symptoms of Spinal Muscular Atrophy

The symptoms of SMA vary depending on each child and when symptoms first appear. Generally, the later symptoms appear in life, the less severe the SMA diagnosis.

The following are symptoms parents may see in a child with SMA:

  • Fasciculations (quivering tongue)
  • Muscle thinning
  • Decreased muscle tone
  • Weak cry
  • Difficulty chewing and swallowing
  • Tire quickly during feeds
  • Inability to hold head up
  • Inability to roll or sit
  • Trouble lifting or carrying items
  • Scoliosis or kyphosis
  • Breathing problems

Treatment of Spinal Muscular Atrophy

While there is no cure, there is SMA treatment available, which will alter the natural course of the disease. This treatment varies based on severity of symptoms and age. The treatment will be used as a tool to help relieve symptoms and sustain mobility. There are currently three FDA-approved treatments available for spinal muscular atrophy.

Pediatric Neurology