Spinal muscular atrophy (SMA) and spina bifida are distinct conditions that affect the nerves that allow for voluntary motor control.

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SMA is a group of genetic conditions that gradually affect motor neurons. These are the nerve cells in the spinal column and brain stem that allow for voluntary muscle control. Spina bifida is a congenital abnormality that primarily affects the spine. They are distinct conditions that share some symptoms, such as weakness in the legs.

According to the Centers for Disease Control and Prevention (CDC), spina bifida affects 1 in every 2,758 births in the United States. Spina muscular atrophy is less prevalent, affecting 1 in every 10,000 live births.

This article takes a closer look at SMA and spina bifida and explores their similarities and differences.

The symptoms of SMA often include:

  • muscle weakness that becomes increasingly worse
  • hypotonia, or muscle tone issues
  • breathing, swallowing, and eating problems
  • problems with walking and speaking

SMA is a rare condition with symptoms that often resemble other conditions. Estimates suggest that fewer than 5,000 people in the U.S. have SMA.

People with SMA tend to have atypical changes in their SMN1 genes. There are four types of SMA, of which the most common is SMA1.

Without treatment, many children with SMA1 cannot sit or walk properly and may have severe breathing problems by the age of 2 years. However, with treatment, children with SMA1 can live longer and reach milestones such as sitting and walking.

Children with SMA2 tend to survive until they are adolescents or young adults. Often, people with SMA3 who receive treatment have typical lifespans and can walk independently. However, they may need help with activities such as climbing stairs.

Explore more about SMA.

Spina bifida occurs when the neural tube, a specialized set of cells that form during the first month of pregnancy, does not close properly.

Usually, the top portion of the neural tube develops into the brain, while the bottom part forms the spinal cord and surrounding structures. In people with spina bifida, the neural tube does not close properly, and some spinal bones do not seal.

The symptoms of spina bifida depend largely on its severity. Mild forms of the condition may cause no symptoms.

More severe cases of spina bifida may cause:

  • trouble with bladder and bowel control
  • learning disabilities
  • leg weakness
  • meningitis, or swelling of the brain
  • skin ulcers
  • brittle bones
  • kidney failure

Children with more severe forms of spina bifida may require surgery. With proper treatment, most children born with the condition have typical lifespans.

Doctors recommend that people intending to become pregnant should take 400 micrograms of folic acid a day to help prevent a fetus from developing spina bifida while in the womb.

Read more about spina bifida.

Though SMA and spina bifida are distinct conditions, they can cause similar symptoms that often affect the spine.

Both spina bifida and SMA may cause:

  • muscle weakness, especially in the legs and arms
  • difficulty or inability to walk or use the legs
  • spine abnormalities
  • breathing problems
  • trouble swallowing

Major differences between spina bifida and SMA include the below.

  • The symptoms of SMA tend to progressively worsen, while signs of spina bifida are typically present at birth.
  • People with SMA may experience muscle twitching, which is not a symptom of spina bifida.
  • Doctors can diagnose and occasionally treat spina bifida before birth, unlike SMA.

In addition, some forms of spina bifida can cause symptoms that do not typically happen with SMA, such as:

  • sleep apnea
  • depression
  • kidney failure
  • male infertility
  • trouble controlling the bowel and bladder
  • learning disabilities
  • brain infections and an atypical buildup of pressure in the brain
  • skin ulcers
  • low bone mineral density

Spina bifida and spinal muscular atrophy (SMA) are distinct conditions that share some similarities.

While SMA is a genetic condition that tends to cause worsening symptoms over time, spina bifida is a congenital abnormality typically present at birth.

Both SMA and spina bifida have a range of symptoms and severity. Treatment aims to improve function, assist with mobility, and prevent complications from developing. Severe forms of SMA and spina bifida require regular care and may significantly reduce a person’s lifespan.