A diagnosis of spinal muscular atrophy (SMA) is usually confirmed by genetic testing.
Genetic testing is used to check for faulty genes. To do this, a blood sample will be taken for analysis.
If you or your child are referred for genetic testing, the doctor will ask about your family's medical history to see if there are neuromuscular conditions in your family. Neuromuscular conditions are those that affect the nerves and muscles.
A physical examination will also be carried out. The examination will look for signs of things such as:
- muscle weakness and wastage
- reduced or absent tendon reflexes
- twitching of individual muscle fibres
Several other tests, such as an electromyography test or a muscle biopsy may be carried out to help confirm a diagnosis of SMA. These two procedures are described in more detail below.
Electromyography
During an electromyography (EMG) test, a thin needle is inserted through your skin and into your muscle.
The needle is used to detect the electrical currents of the muscle, both at rest and during activity. This can help determine whether any muscle weakness is caused by a disease in the muscle itself or is the result of a lack of nerve supply. A lack of nerve supply indicates SMA.
Muscle biopsy
During a muscle biopsy, a small sample of muscle tissue is taken for analysis. The sample, which is usually taken from the thigh, is examined under a microscope. However, with the wide availability of genetic testing, muscle biopsies are rarely done nowadays to diagnose SMA.
