Spinal Muscular Atrophy and Muscular Dystrophy

  • Spinal muscular atrophy (SMA) refers to a group of inherited neuromuscular diseases that affect the nerve cells and the control of voluntary muscles. SMA causes lower motor neurons in the base of the brain and spinal cord to disintegrate, preventing them from delivering the necessary signals for normal muscle function.
  • Bladder and bowel function and hearing and vision are not affected. Also, intelligence remains normal or above average.
  • It is the number one genetic killer of infants and toddlers.

Types of SMA

Type I is the most severe form of SMA. It predominantly affects neurons controlling the mouth and throat muscles and causes problems chewing, sucking, and swallowing. In most cases, various respiratory muscles are affected as well. This type of SMA usually occurs in infants from 0 to 6 months.

Type II is an intermediate form of SMA. One can learn to sit without support but cannot stand or walk without aid. Swallowing and respiratory problems are prevalent. Onset begins at 6 to 18 months of age.

Type III is a milder form of SMA. Weakness of the muscles in mouth and throat is rare, as well as respiratory problems. Individuals with this type of SMA have a normal lifespan, fewer symptoms and complications, and can ambulate at some point in life.

What is Muscular Dystrophy?

  • Muscular dystrophy (MD) is caused by anomalies in genes for muscle proteins. Most of these proteins appear to play a role in supporting the structure of muscle fibers, but some may play a role in the biochemical processes that go on in muscle fibers.
  • The term muscular dystrophy refers to a group of genetic diseases marked by progressive weakness and degeneration of the skeletal, or voluntary, muscles, which control movement.
  • The muscles of the heart and some other involuntary muscles are also affected in some forms of muscular dystrophy, and a few forms involve other organs as well.

Forms of MD

  • The major forms of muscular dystrophy are myotonic, Duchenne, Becker, limb-girdle, facioscapulohumeral, congenital, oculopharyngeal, distal and Emery-Dreifuss.
  • Although there are specific forms of MD with a variety of signs and symptoms, the ones listed here are the most common and prevalent among individuals with MD. For more specific symptoms, please visit our website.

Signs & Symptoms:

  • Muscle weakness
  • May walk with a waddle or gait
  • Loss of balance and coordination
  • Use of some form of durable medical equipment
  • Joint stiffness/spasticity
  • Scoliosis


  • Learning disabilities
  • Heart/cardiac problems
  • Poor respiratory functioning

Note: Due to the overall weakening of muscles in people who have MD, positional asphyxiation is more likely. DO NOT place a person with MD on their stomach, side, or another position that could compromise and make his or her breathing more difficult.