Spinal Muscular Atrophy



Spinal muscular atrophy (SMA) is a genetic condition that affects the nerves which control muscle movement – the motor neurons.

SMA is classified into types 1 to 4 depending on severity. Babies with SMA type 1 rarely live beyond three years of age, whereas people with type 4 have a normal life expectancy.

It is named ‘spinal’ because most of the motor neurons are located in the spinal cord. ‘Muscular’ is in the name because it mainly affects the muscles that don’t receive signals from the motor neurons. ‘Atrophy’ is the medical term for wasting away or getting smaller, which is what generally happens to muscles when they’re not active.

SMA affects muscles throughout the body, although the muscles closest to the trunk of the body – the shoulders, hips, and back – are often most severely affected. Sometimes, feeding and swallowing can be affected. Involvement of respiratory muscles (muscles involved in breathing and coughing) can lead to an increased tendency for pneumonia and other lung problems.

Sensation and the ability to feel are not affected. Intellect is normal and it is often observed that people with SMA are bright and sociable.

SMA is a relatively common ‘rare disorder’. Approximately one in 6,000 babies born is affected, and about one in 40 people are genetic carriers. There is no cure, but there are some promising treatments being tested in clinical trials.