Spinal muscular atrophy

Atrophy is a partial or complete wasting away of any given body part. Most commonly, however, muscles atrophy for a variety of reasons. In the case of spinal muscular atrophy (SMA), the atrophy is an inheritable condition; it is a group of inherited diseases that result in the gradual degeneration of the spinal muscles. Eventually, it leads to death. The symptoms are obvious, and it is typically diagnosed in the early years of life. Life expectancy depends on the type of SMA an individual has. There is no treatment.

What happens?
In those with spinal muscular atrophy, nerve cells (called motor neurons) are attacked. These neurons are responsible for communicating with the muscles that you voluntarily control, like the arms and legs. The neurons start to die off, communication becomes poor, and gradually, the muscles weaken. Think of these few things and how much your body depends on muscle for them: crawling, walking, breathing, swallowing, and head and neck control. It probably isn’t something you consciously think about, how much you depend on your muscles, but indeed you do. When muscle control is lacking, these movements cannot happen.

Types of SMA
There are different types of spinal muscular atrophy. However, all are somehow inherited. The parents don’t usually have symptoms of the disease, but obviously one or both carries the gene.

Mutation of SMN gene
The most common cause of spinal muscular atrophy is due to a mutation of the survival motor neuron (SMN) gene. It affects anyone from infants to adults.

Mutation of other genes
Other mutations can also result in SMA; not all of them are identified as of today. The similar connection between the mutations is that something causes the muscle fibers to lose connection with the muscles in the spinal cord that communicate when to contract.

Symptoms in an infant include difficulty breathing, difficulty feeding, poor muscle tone, lack of head control, little spontaneous movement, progressive weakness from infant to toddler, very weak infant. Symptoms in a child include frequent and increasingly severe respiratory infections, nasal speech, and worsening posture.

There are different tests that can confirm a diagnosis of spinal muscular atrophy. They include CPK levels, DNA testing, electromyography, MRI of the spine, and a muscle biopsy. Also, a family history will be taken and a muscle and reflex test of the affect infant or child.

The prognosis ultimately depends on the type of SMA the individual has. Those with Type 1 (Werdnig-Hoffman disease), which is the worst, only live to 2-3 years of age; those with type 2, which is not as bad, usually don’t make it through childhood; and those with type 3 can survive until later in life because it is a less severe form of the disease.


There is no treatment for this progressive disease. The only way to treat it is to essentially prevent it by having genetic counseling before a couple decides to have children. Secondary to that, it is important to closely monitor an individual with spinal muscular atrophy. Close attention should be paid to the respiratory system because the muscles that are responsible for breathing become increasingly weak, and so bacteria can easily accumulate. Respiratory infections are quite common among those with SMA, and they can get worse and worse as time goes on. Complications from these infections are quite common. Physical therapy is also an important component to an individual’s lifestyle because it prevents the muscles and tendons from contracting and the spine from curving abnormally. Wearing a brace may be necessary in some cases. In this day and age, there is a lot of technology available, such as motorized wheelchairs and ventilators, which makes things easier in the daily lives of individuals with SMA.

Last updated on Feb 11th, 2011 and filed under Neurological Disorders. Both comments and pings are currently closed.

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