What is Spinal Muscular Atrophy?

Spinal Muscular atrophy (SMA) is a genetic disorder affecting motor neurons that control voluntary muscle movement. SMA causes the brain to stop sending messages that control muscle movement due to the breakdown of nerve cells, and consequently, muscles weaken due to inactivity. SMA most commonly affects babies and young children, making it hard for them to develop.

One in every 6,000 babies is born with SMA, and it is one of the most prevalent genetic disorders affecting young children and a major cause of death in infancy. Although it can strike children at any age, more positive prognoses are associated with older children.

The extent of symptoms and subsequent treatment options for SMA depends on the type of SMA they have. It is divided into subtypes 1-4 based on 1) the age of symptom onset and 2) the maximum motor function achieved. There is also a rare form of SMA not linked to chromosome 5 that involves muscles farther away from the center of the body.

At the moment, there is no solve-all cure to spinal muscular atrophy, but there are several treatment options that can improve symptoms and, in some cases, help patients live longer. These disease-modifying therapies have shown optimistic results and have full FDA approval.

Types and Causes of Spinal Muscular Atrophy


SMA is caused by the mutation or omission of the SMN1 gene (located on the 5th chromosome) that encodes the survival motor neuron (SMN), a protein that plays a key role in both the functioning and maintenance of motor neurons. Without the ability to make this kind of protein, muscles are not enabled to receive movement signals from the nerves.


SMN is inherited through an autosomal recessive pattern. It is a genetic disorder that occurs when an individual receives two copies of a broken gene, one from each parent. If an individual received it from just one parent, they would be considered a carrier of the disease, but likely have no symptoms. 


The SMN2 gene can partially compensate for the loss of the SMN1 gene, and patients with more or fewer copies of this gene have varying degrees of functionality based on their ability to compensate. In other words, more copies of the SMN2 gene generally result in milder disease.

Spinal muscular atrophy is broken down into types 1-4 and non-chromosomal. Most cases are progressive meaning that symptoms worsen instead of improving. Generally, the later in life that symptoms develop the better the disease can be managed and treated.

Type 1: Infantile-onset SMA or Werdnig-Hoffman disease

Type 1 is the most severe kind of SMA seen in infants within the first six months of life. In these cases, children may not be able to support their heads or sit up without assistance. There is concern that weakness in muscles that control breathing may occur, and in these cases, most children do not live past the age of 2.

Type 2: Intermediate SMA

Type 3 develops in children 18 months and older. In these cases, muscle weakness occurs but patients can typically walk or stand for limited amounts of time. Later in life, wheelchairs or other assistive devices may be needed for mobility.

Type 3: Juvenile SMA or Kugelberg-Welander Syndrome

Type 3 develops in children 18 months and older. In these cases, muscle weakness occurs but patients can typically walk or stand for limited amounts of time. Later in life, wheelchairs or other assistive devices may be needed for mobility. 

Type 4: adult SMA

Type 4 SMA is linked to the rare development of the disease in adulthood. These cases are usually not severe enough to affect lifespan. Although symptoms will persist, there are physical therapy remedies and treatment centers readily available to manage this form of the disease. 

SMA not linked to chromosome 5

Some forms of SMA are not linked to the SMN1 gene that produces the SMN protein deficiency. These types vary in severity. 

Signs and Symptoms of Spinal Muscular Atrophy

Spinal muscular atrophy symptoms vary a lot depending on the type of SMA a patient has. They can range from mild to severe and/or disabling. Typically, muscles closest to the center of the body are affected. In some cases, if the disease progresses, breathing and swallowing challenges can seriously impact the lifespan of a patient. SMA does not affect involuntary muscles or affect a person’s intelligence. The occurrence of SMA is approximately 1 in 10,000 live births, and SMA affects females and males equally. 

Diagnosis and Treatment of Spinal Muscular Atrophy

SMA can be a hard disease to diagnose, especially in infant children. There is a baseline of questions and tests available to help decipher if you or your child may be symptomatic of SMA. Further, based on the type of SMA that you or your child might have, there are a variety of treatment options and spinal muscular atrophy treatment centers available to help manage the disease. Rest assured, there are options to increase the quality of life and be proactive in fighting this disease.


In order to get a proper diagnosis, you’ll need to connect with your doctor to determine your symptoms and official diagnosis.

At Home Questions:

Ask these baseline questions if you suspect your child might be symptomatic of SMA: 

  • Has your baby missed any developmental milestones (holding their head up, rolling over, etc)?
  • Does your child have trouble sitting or standing on their own?
  • Have you seen your child have trouble breathing? Swallowing? 
  • When did you first notice the symptoms?
  • Has anyone in your family had similar symptoms?
  • Do you have a genetic predisposition to SMA? Are you (the parent) a known carrier?

Genetic testing

Your doctor can order tests to help diagnose you or your child. A simple blood sample could check to see if any missing or broken genes might cause SMA. Specifically, they look for mutations of the SMN gene on the fifth chromosome. Further, a blood test that checks for CK/creatine kinase could be helpful as this reveals an enzyme that leaks out of weakening muscles.


An EMG (electromyogram) is a nerve test that sends electrical impulses through the nerves to see if they are sending messages to the muscles.

Muscular Biopsy

This test removes a small piece of muscle for examination under a microscope. 

CT Scan

A CT scanner is a powerful machine that makes detailed pictures of the inside of the body. This could help reveal muscle deterioration. 

SMA Treatments

At present, there is no cure for SMA. Affected patients can work with a health care team to manage their symptoms, prevent complications, and improve their quality of life and lifespan. Here is a guide to assembling your care team and treatment plan: 

The Right Doctor

Ask your doctor these baseline questions to make sure you are getting the best possible care and most informed results: 

  • Have you treated others with this condition?
  • What treatments do you recommend?
  • What kinds of therapy do you recommend?
  • What can I do to help my child become more independent?


The FDA has approved three medications to treat SMA:  

  • nusinersen (Spinraza): which adjusts the SMN2 gene and lets it make more protein; used in both children and adults 
  • onasemnogene abeparvovec-xioi (Zolgensma): involves replacing the problem SMN1 gene; used for children under 2 years of age
  • risdiplam (Evrysdi): treatment to stop the SMN2 gene from disrupting the protein production. 

Several other medications to improve muscle and nerve functions are currently in clinical trials, and research has made significant progress in recent years.

Support Devices and Therapies

Depending on the symptomatic area, there are other devices and/or therapies a doctor could advise to treat and manage systems. Wheelchairs, braces, and support devices can improve mobility and keep the patient independent for longer. In some severe cases where respiratory troubles are at play, a doctor could advise special masks or mouthpieces to help with breathing. Further, if nutrition levels are being affected, feeding tubes might be helpful for babies and young children.

Doctors You Might Need

There are a lot of things you can do to improve your child’s quality of life. These specialists can help make decisions about the patients’ health and help organize the management of their care. This is a list of doctors needed for lifelong care and treatment:

  • Pulmonologists – lungs
  • Neurologists – nerve problems
  • Orthopedists – bone problems
  • Gastroenterologists – stomach disorders
  • Nutritionists – food and nutrition
  • Physical therapists – exercise to improve motion

Note; physical therapy to keep joints flexible and slow the progression of muscle wasting and proper feeding to avoid aspiration are essential elements to treatment plans.

Finding a Treatment Center

Keep in mind that every child or adult who has SMA will have a different experience. Creating a treatment plan custom-made for your child will help them have a better quality of life. 

We recognize that it can be extremely overwhelming and isolating to have a child with complex medical conditions. 

George Mark Children’s House Programs develop an individualized care plan for each child, coordinating services among the George Mark care team—pediatricians, nurses, nursing assistants, social workers, child life specialists, palliative aquatics specialists, psychologists, support staff, and volunteers.

We partner with families to bring an element of normalcy and joy into their lives. In addition to our around-the-clock skilled pediatric nursing, we offer everyday activities including play, art, music, movement, and hydrotherapy

Here at George Mark Children’s House, we offer:

  • Transitional care for children who are no longer benefiting from an acute care hospital yet are not able to be cared for at the home
  • End of life care so that a patient’s family can stay in its family suite and surround their child with love and support
  • Respite care for high-quality medical care and appropriate activities, while offering parents and families a short break from the nonstop care at home
  • Bereavement care, offering ongoing support to families following the death of their child