In spinal muscular atrophy, there is a loss of important cells in the spinal cord called motor neurons, which are essential for muscle strength and movement. These motor neurons regulate muscle activity by sending signals from the central nervous system (CNS), which is the part of the body’s nervous system that includes the brain and spinal cord.^1,2

The loss of functioning motor neurons leads to progressive muscle weakness and atrophy (the gradual decrease in the mass and strength of muscles), as muscles stop receiving signals from the CNS.³

Unlike many other rare neuromuscular diseases, there is a clear understanding of the specific genetic cause of spinal muscular atrophy.

Every child with spinal muscular atrophy is affected differently, and it is important to note that symptoms can vary greatly according to the age of onset and disease severity. Children may experience progressive muscle weakness in the muscles closest to the centre of the body, such as the shoulders, thighs, and pelvis. These muscles enable activities such as crawling, walking, sitting up, and controlling head movement. Breathing and swallowing may also be affected.⁷

Spinal muscular atrophy does not affect the neurons responsible for cognition, which is the mental process through which we gain knowledge and understanding through thought, experience, and the senses.^8.9 According to one study, children and adolescents with spinal muscular atrophy have normal intelligence, with IQs in the standard range. Intelligence, cognitive, and behavioural testing may help to prevent school-age children from being bored, under-challenged, or frustrated.¹⁰

If you have a family history of spinal muscular atrophy, your chances of being a carrier are greater than average. In making reproductive decisions, it may be helpful to consult with your physician to learn what mutation(s) are common in your family. Once your family mutation(s) are known, an appropriate test for your situation may be determined:

• If your family mutation(s) are SMN1 deletions, then copy number testing may be appropriate for you
• If your family mutation(s) include a more subtle change in the gene, then your physician and the laboratory may decide whether testing can be done to look for that specific change

If you are unable to obtain your family mutation(s) information, you can still have a copy number test performed. Your chance of being a carrier (before you have testing) will be calculated from your family history. If your results are normal, your chance of being a carrier may be lower.

Speak to your doctor for more information.