Spinal muscular atrophy (SMA) is a group of hereditary diseases that gradually destroy motor neurons. SMA can be fatal if not treated or not caught early enough, but modern screenings can help identify SMA earlier and also help determine whether you and your partner are carriers.

Carriers have one copy of the defective gene. To develop SMA, your child typically needs two copies of the gene (one from you and one from your partner). If you’re both carriers, your child has a 25% chance of developing SMA.

SMA affects about 1 in 10,000 babies born in the United States.

Keep reading for more information on how doctors screen for SMA, its causes, diagnosis, and possible treatments.

Screenings the risk of SMA can occur before conception. During pregnancy and after birth there are screenings for the condition itself.

SMA is a recessive condition. This means that for your baby to develop SMA, they’d need to inherit a copy from both you and your partner.

If you’re concerned that you may carry the recessive gene, you can get carrier screening. Carrier screening for SMA requires a blood draw and is about 90% effective in detecting carriers.

If you receive positive results, you may want to have your partner tested as well. In rare cases, your baby may be born with SMA not caused by the mutations tested for in carrier screening.

Once you become pregnant, there are tests to screen for SMA in your first and second trimesters:

  • chorionic villus sampling (CVS) at 10 to 14 weeks
  • amniocentesis at 16 to 20 weeks.

Since 2018, SMA screening shortly after birth has been a routine test in 48 U.S. states. Healthcare professionals draw a small amount of blood from the heel and test your newborn for various genetic conditions, including SMA.

Early detection can help improve your baby’s outcome because it can allow healthcare professionals the opportunity to monitor and treat SMA quickly. Doctors can treat the condition with nusinersen (Spinraza), a medication that can help prevent SMA from getting worse.

When caught early, treatment can begin before symptoms start. Symptoms vary based on the type of SMA and may include:

  • Type 0: They have decreased muscle tone, reduced fetal movement, inability to reach milestones, heart defects, and severe weakness.
  • Type 1: They have trouble sucking, swallowing, or breathing and very weak, never reach the milestone of sitting on their own.
  • Type 2: They have muscle weakness that may prevent standing or walking but likely won’t affect the face.
  • Type 3: They may be able to stand and walk, but muscle weakness will slowly cause issues with mobility later in life.
  • Type 4: They reach all their milestones, and symptoms of weakness in proximal muscles occur in later teen years or adulthood.

Type 0 or 1 are the most severe types and are associated with early death by age 2. Modern therapies can help keep babies alive when administered quickly after diagnosis.

SMA occurs due to changes in your baby’s genes that affect their motor neurons.

The most common form of SMA occurs from changes to the survival motor neuron 1 gene (SMN1) on chromosome 5q. The gene is responsible for making survival motor neuron (SMN) proteins.

Without these proteins, your baby’s muscle neurons disappear, which leads to muscle weakness and wasting away of their muscles. This can quickly lead to mild to severe symptoms that can be deadly in more severe forms.

In most cases, to pass it on, both you and your partner have to pass the defective or missing gene on to your child. In other words, for your child to develop SMA, they need two defective copies.

If they only get one bad copy, they won’t have any symptoms and become a carrier themselves.

In most U.S. states, doctors order newborn blood draws to check for various conditions, including SMA. This screening process is about 95% effective in detecting SMA. A doctor may order additional testing or refer your baby to a neurologist for further testing and diagnosis.

If your child is older, a doctor may look for signs and symptoms that could indicate SMA. Some symptoms they check for can include delays in:

  • walking
  • sitting independently
  • holding their head up
  • standing
  • rolling over
  • other motor milestones

If they suspect SMA, they’ll likely order genetic testing or refer your child to a neurologist for proper diagnosis.

Early detection and treatment can generally improve outcomes. According to one article, recent innovations in treatment have changed therapeutic approaches for type 1 SMA from palliative care with the expectation of early death to treatments that can help a child grow and thrive.

Currently, there’s no cure for SMA, but recent advancements can help keep your child healthy and delay or possibly prevent fatality.

The Food and Drug Administration (FDA) approved nusinersen (Spinraza) in 2016 for both children and adults. The injection is safe for both children and adults and helps to increase the production of SMN proteins.

Another therapy, onasemnogene abeparovec-xioi (Zolgensma), became available in 2019 as an option in children younger than 2. The medication targets motor neurons to help improve muscle movement and function.

In 2020, the FDA approved risdiplam (Evrysdi) for children over the age of 2. It’s similar to Zolgensma.

In addition to therapies, you may want to consider therapies for your child such as:

  • stretching exercises
  • occupational
  • physical therapy
  • rehabilitation
  • speech
  • providing good nutrition
  • assistive devices, such as braces or wheelchairs

You can build a care team for your child based on their physical needs. A care team may consist of several different doctors and therapists, such as:

  • speech, occupational, physical, or other therapist
  • neurologist
  • pediatrician
  • nutritionist

Researchers continually look for new and effective treatments for SMA. Since the gene discovery, scientists have been looking for ways to effectively treat and manage SMA.

If you’re interested, you can talk with a doctor about having your child join a clinical study. Clinical studies help researchers find new treatments and may one day provide a cure for SMA. For example, researchers are continuing to research gene replacement therapy for people with SMA.

Several screenings both before and after birth can help determine whether your child has SMA. Early diagnosis can help improve your child’s overall outlook.

Treatments often involve the use of medications to help stop continued progression as well as various therapies. You may also want to get your child involved in a clinical trial to help discover new therapies and potentially a cure one day.