By Dr_Trisha-Macnair Published 01/21/2016 16:07:00 | Views: 544

What is it?

Spinal muscular atrophy (SMA) is a condition that affects the nerves in an area of the spinal cord called the anterior horn. These nerve cells become damaged, breaking the link between the brain and the muscles. As a result, the muscles can't be used and become wasted or atrophied.

SMA affects the voluntary muscles (especially those closest to the trunk of the body) used for activities such as crawling, walking, head and neck control and swallowing.


There are several different types of spinal muscular atrophy: type I (severe, also known as Werdnig-Hoffmann syndrome), type II (intermediate) and type III (mild, also known as Kugelberg-Welander disease) affect children, while there are a variety of types of adult-onset SMA that develop later in life.

Type I may begin before birth (lack of foetal movement in late pregnancy) or shortly afterwards, and an affected baby is rarely able to lift his head or develop normal movement. Swallowing, feeding and breathing may be difficult, and the child rarely survives to the age of two.

Type II usually appears in the first couple of years. The child may reach adulthood, although they may need help to sit or stand, and strain on the muscles can cause complications.

Type III may be diagnosed as late as adolescence. Those affected may have problems walking or getting up from sitting.

Unlike types I, II and III, which aren't usually progressive, adult-onset SMA tends to progress very slowly, although it's not usually life-threatening. Symptoms are variable and depend on the muscles affected. Fatigue may be a problem, but the muscles used for swallowing and respiratory function are rarely affected.


Types I, II and III SMA are autosomal recessive conditions and affect boys and girls equally. It's estimated that more than 1 million people are carriers of SMA.

Adult-onset SMA may be autosomal recessive, autosomal dominant or X-linked recessive (a form of SMA known as Bulbo-SMA or Kennedy's syndrome). In a few cases, adult-onset SMA results from genetic mutations acquired during life rather than inherited.


Currently, there is no cure or treatment to repair the nerve damage, but support care including physio and respiratory drainage are very important. Within affected families, once the abnormal gene has been identified, carriers can be detected by a blood test, and antenatal screening using CVS (chorionic villus sampling) is available.

By Dr_Trisha-Macnair 01/21/2016 16:07:00

Subscribe to comments feed Comments (0)

total: | displaying:

Post your comment. Registration not required

  • Bold
  • Italic
  • Underline
  • Quote

Please enter the code you see in the image: