What are the symptoms of SMA (Spinal Muscular Atrophy)?

Did you know that 1 in 10,000 children and adults in the United States (CDC [Centers for Disease Control &Prevention] statistics) are affected by Spinal Muscular Atrophy (SMA)?  

August is officially celebrated as SMA awareness month all over the US. Let’s look at the signs and symptoms of SMA to understand the disease better. 

Spinal Muscular Atrophy (SMA) is a genetic neuromuscular disorder that affects the ability of your motor neurons to control the voluntary muscles in your body and is characterized by the wasting away of the muscles. Infants, children, and adults of any color or gender can be affected by the disease. There are five clinical types of SMA (types 0,1,2,3,4) and they are distinguished by the severity and the age of onset of the symptoms. 

What happens in SMA? 

SMA is caused due to a genetic mutation in the SMN1 gene (that makes the SMN protein) required for healthy motor neurons.  

These motor neurons (in the spinal cord and the lower part of the brain) that control muscle strength and movement deteriorate. They are unable to send signals from the brain to the muscles, causing them to move. Because the muscles do not move, they shrink (or atrophy). 


People with SMA experience progressive loss of movement, strength, and control of the muscles in various parts of the body. SMA can affect: 

  • Nervous system: SMA leads to defective motor neurons (the special nerves in the spinal cord and lower part of the brain responsible for controlling muscles and movement) leading to impaired motor function, leading to: 
      • floppy or weak arms and legs  
      • movement issues, such as difficulty sitting up, crawling, or walking 
      • muscle twitching or shaking (tremors)
  • Heart: SMA is also associated with Cardiomyopathy. Some people may also experience symptoms, such as: 
      • Breathlessness during physical exertion or at rest 
      • Coughing while lying down 
      • Fatigue 
      • Rapid, pounding, or fluttering Heartbeat  
      • Discomfort or pressure in the chest 
      • Swelling (mostly in Legs, ankles, and feet)  
      • Feeling dizzy, lightheaded, or fainting (syncope) 
      • Bloating or swelling in the abdomen 
  • Lungs: In many cases of SMA, weak respiratory muscles make coughing difficult and clear out mucus, resulting in an increased risk of serious infection of the lungs. A simple cold can quickly develop into something severe like pneumonia. As the respiratory muscles weaken, the following symptoms start to appear: 
      • Breathing difficulties  
      • Respiratory infections  
      •  Chest infections  
      •  Respiratory failure (in severe cases) 

 The symptoms of breathing problems can also include: 

      • Headaches 
      • Difficulty sleeping at night  
      • Excessive sleepiness during the day 
  • Gastrointestinal system: An infant with SMA presents with dysphagia (sucking and swallowing difficulties) caused by muscle weakness in the throat and mouth. SMA also affects chewing, speech, and swallowing, resulting in fasciculations (quivering) of the tongue.  
  • Muscles: SMA is characterized by deterioration and wasting away of muscles and symptoms include: 
      • Muscle weakness  
      • Hypotonia 
      • Fatigue  
      • Spasticity 

SMA can impair a child’s ability to crawl, walk, sit up, and move his or her head. The muscles closest to the center of the body (such as the shoulders, hips, thighs, and upper back) are the most affected. The lower limbs are more affected than the upper limbs, and deep tendon reflexes are reduced.  

If the muscles used for breathing and swallowing are affected, this results in abnormalities in breathing and eating. Kyphosis and scoliosis (Spinal curvatures) can develop if the back muscles weaken. 

  • Bones: SMA affects the skeletal muscles (muscles responsible for movement) and can lead to effects on the bones as well, like: 
      • Bone fractures  
      • Contractures and joint deformities 
      • Hip dislocation  
      • Scoliosis-Scoliosis is a type of abnormal spinal curvature (side to side) caused by a weakness in the muscles that support the spine. Scoliosis can be extremely painful, impair position and mobility, and harm a child’s (or adult’s) body image. Some studies have found that severe spinal curvatures can interfere with breathing also. 
      • Kyphosis-An abnormal forward curvature of the spine caused by weakened muscles that are unable to keep the spine straight. 

Diagnosis & Management 

  • Prenatal tests can determine if your unborn baby has SMA (if you are pregnant and have a family history of the disease).  

SMA prenatal tests include: 

    • Amniocentesis: It’s a procedure in which your obstetrician inserts a thin needle into your abdomen to extract a small amount of fluid from the amniotic sac and examines the fluid for SMA. This test is usually done after the 14th week of pregnancy. 
    • Chorionic villus sampling (CVS): Your obstetrician extracts a small tissue sample from the placenta. CVS can be done as early as the tenth week of pregnancy. 
  • SMA screening programs (newborns) 

State public health laboratories use dried blood spots collected from a baby’s heel within the first 24-48 hours of birth in routine newborn screening to detect genetic disorders such as SMA. 

    • Your doctor may take a detailed history and order several tests, including: 
    • Creatine kinase (CK) activity (blood test) 
    • Genetic examinations 
    • Electromyogram and other nerve tests (EMG) 
    • CT scans 
    • MRI 
    • Biopsy of muscle tissue 

 SMA has no known cure, but these treatments can benefit patients:  

  • Medications like  Nusinersen (Spinraza), Onasemnogene abeparvovec-xioi (Zolgensma), and Risdiplam (Evrysdi) have been shown to improve symptoms like respiration, motor function, and overall survival. 
  • Breathing assistance by a breathing machine or mask/mouthpiece, a breathing apparatus, or in extreme cases a tracheostomy is performed. 
  • Proper diet and nutrition to prevent nutritional deficiencies and dehydration.  
  • Medicine, physical therapy, occupational therapy, and occasionally surgery are used to treat scoliosis. 
  • Groups for counseling and support 

SMA is a rare genetic motor neuron disease that needs a team effort to manage, diagnose and live with. This team includes parents, medical professionals, nurses, therapists, counselors, and a dietitian. The outlook for children with SMA has improved because of medical advancements. 

At Doral Health and Wellness, we have doctors that can help you manage your condition. For more information, you can visit us at 1797 Pitkin Avenue, Brooklyn, New York, 11212, or call us at 1-347-384-5690. You can also visit our website at https://doralhw.org or contact us at info@doralhw.org if you have any queries.