Spinal Muscular Atrophy: Signs, Causes, Treatment

Spinal muscular atrophy, is a condition affecting children and babies. It affects muscle movement. And a child may experience difficulties in breathing and swallowing as the condition progresses.

Physical Therapy and Rehabilitation for Spinal Muscular Atrophy

A condition that often affects children and babies is known as spinal muscular atrophy or abbreviated as SMA. It affects muscle movement. As the disease progresses, a child may experience difficulties in breathing and swallowing. Learn more about this disease and how it is treated.

What is Spinal Muscular Atrophy?

In a child that has been diagnosed with SMA, there is a breakdown of nerve cells, particularly the motor neurons. It affects the spinal cord and brain. The brain halts messages that aid in muscle control and movement. When this happens, the muscles weaken and shrink. The movement that involves controlling the head, walking, and sitting may become difficult for the child.

Types of SMA

  1. Type 1 or Acute Infantile SMA: This is also known as Werdnig-Hoffman disease and is the most extreme type of SMA and may develop before delivery. During the last three months of pregnancy, mothers may notice weak fetal movements. A large portion of children affected by this SMA type may manifest symptoms before turning eight months. This condition affects muscles in charge of swallowing and chewing. It also affects the muscles in the legs, arms, and chest.
  2. Type 2 or Chronic Infantile SMA: Chronic infantile SMA progresses slowly and is less severe than type 1 SMA. The symptoms manifest between 6 to 18 months old. Children may develop orthopedic problems and may need a wheelchair for movement. Kyphoscoliosis may also occur.
  3. Type 3 or Juvenile SMA: It is also known as Kugelberg-Welander disease, and the symptoms manifest between 2 to 17 years old. The condition progresses slowly but may the severity of this condition can vary per individual. While some children have difficulties standing or walking, others do not develop problems in these areas.
  4. Type 4: This form begins at adulthood and usually affects the legs and upper arms.


This illness is instigated by an autosomal recessive gene. It means that both parents carry the mutated gene. The particular gene affected in this disease is the “survival of motor neuron” gene, which is SMN1 and 2. In some cases, approximately 95 percent, both the SMN1 genes are absent.

In cases where both parents have the mutated gene, there is a 25 percent chance that the pregnancy leads to a child with the disease.


Symptoms of the disease depend on the type of SMA. The common symptoms, however, include the following.

  • Breathing Problems
  • Delayed Gross Motor Skills
  • Decreased Muscle Tone
  • Limited Mobility
  • Muscle Weakness
  • Problems Swallowing and Eating
  • Spontaneous Movements of the Tongue
  • Scoliosis

A child may exhibit floppy movement of the legs and arms. Problems with swallowing are also noted. Furthermore, the child exhibits difficulties in sitting or supporting one’s head. The symptoms are severe and include the following:

  • Diminished Muscle Tone
  • Feeding and Swallowing Difficulties
  • Muscle Weakness
  • Pneumonia
  • Respiratory Problems
  • Tongue Fasciculation (Quivering of the Tongue)

Children under this type could die due to recurring respiratory infections that happen in the first year of life.

2. Symptoms of Type 2

This type affects children aged 6 to 18 months old. Symptoms are moderate to severe. It also affects the legs. The symptoms associated with this type include the following.

  • Absent or Decreased Tendon Reflexes
  • Diminished Muscle Tone
  • Respiratory Problems
  • Twitching of the Muscles

3. Symptoms of Type 3

The signs of this type start to manifest at ages 2 to 17 years old. Though the mildest form of SMA, a child may still have problems getting up from a chair, climbing the stairs, or running. A wheelchair may also be needed later in life. Other symptoms that may manifest include the following.

  • Weakness in Upper Back and Thighs
  • Weakness in Hips and Shoulders

4. Symptoms of Type 4

As mentioned, this type of SMA happens in adulthood. Symptoms include involuntary contractions, breathing problems, and muscle weakness.


A physical exam is done on the child to diagnose SMA fully. Doctors may also go through the family’s medical history. For a definite diagnosis, the following tests are also done.

  • Gene Test: Changes or defects to the SMN gene provide a definite diagnosis of the disease. Aside from the SMN gene, it can also detect another gene linked to SMA which is the “neuronal apoptosis inhibitory protein” gene (NAIP).
  • Electrodiagnostic Test: This is comprised of two tests, namely the electromyography (EMG) test and the nerve conduction study. For EMG, a needle electrode is inserted in the skin. This measures the muscles’ bioelectrical activity. Moreover, it shows if there is damage to the peripheral nerves.

    For nerve conduction studies, an electrode is stuck onto the skin, specifically over a sensory or peripheral motor nerve. Mild discomfort may occur since a small electric shock is emitted through the electrode. This shock stimulates the motor and sensory nerves which is then recorded to see how fast the electricity is carried and how much of it reaches the nerves.
  • Nerve and Muscle Biopsy: If a genetic test fails in confirming the diagnosis, then this procedure is done. Small samples of the nerve and muscle tissue are taken. These are then examined for signs of SMA.


While there has yet to be a definite cure for the disease, treatment is focused on managing the diseases’ complications and symptoms. Treatments include the following.

1. Medications

One medicine permitted by the Food and Drug Administration is Nusinersen or Spinraza. It slows down the progress of the disease and strengthens the individual affected. The medication is injected into the spinal cord. This works by adjusting or modulating the SMN2 gene.

2. Nutrition

Due to problems with swallowing and chewing, some children may not receive the required amount of nutrients needed by their growing bodies. Doctors work with nutrition therapists to ensure children diagnosed with SMA receive proper nourishment. Gastronomy tubes may be inserted to allow the direct flow of nutritious liquid into the stomach.

3. Physical Therapy

Range-Of-Motion exercises are done to help the child’s muscles remain mobile and flexible. Also, to prevent joint tightness and contractures, night splints are used on the wrists and ankles.

4. Respiratory Support

Respiratory problems are one of the common complications of the disease. Treatments to prevent these complications include breathing devices and breathing exercises. Moreover, supplemental oxygen is administered. Immunizations are also given yearly to prevent illnesses like influenza.

Spinal Muscular Atrophy Signs, Causes, Treatment

Leave a Reply

Your email address will not be published. Required fields are marked *