For diagnosing spinal muscular atrophy (SMA), certain tests are carried out to check if your child has this condition. Also, a few tests may be done to identify if you are at risk of having a child with the condition.
Tests before getting pregnant
Consult a physician if you are planning a pregnancy and
- You had a previous child with SMA.
- You have a history of the condition in your family.
- Your partner has a history of SMA in their family.
Your physician may ask you to undergo genetic counseling to understand the risk of your child having SMA.
Some of the options that the genetic counselor might suggest include
- Getting pregnant and waiting to see if your child is born with SMA.
- Using donated sperm or eggs to get pregnant.
- Pre-implantation genetic diagnosis (PGD) is done after a woman’s eggs are fertilized in the laboratory and the resultant embryos are tested for SMA before they are implanted in the uterus.
Tests during pregnancy
If during pregnancy, you are aware that there is a risk of your child having SMA, the physician might suggest the following tests
- Chorionic villus sampling (CVS): At 11 to 14 weeks of pregnancy, a sample of cells from the placenta is tested.
- Amniocentesis: At 15 to 20 weeks of pregnancy, a sample of amniotic fluid is tested.
If these tests show a positive result, talk to your physician about your future options. Please note that these tests can slightly increase the risk of miscarriage.
Tests after birth
If you or your child exhibit typical symptoms of spinal muscular atrophy (SMA), a genetic blood test can confirm the condition. In genetic testing, a blood test is carried out to check for the presence of the SMN1 gene (survival motor neuron 1 gene).
The physician may also perform the following tests to diagnose SMA
- Physical examination: To look for signs of SMA.
- Electromyography: This involves the insertion of thin needles into a muscle to detect its functioning.
- Muscle biopsy: The physician removes muscle cells through a needle or by making a small cut in your child’s skin.
- Imaging tests: Computed tomography (CT) scan or magnetic resonance imaging (MRI) helps to visualize the organs and structures inside the body.
- Creatinine kinase test: This test helps to distinguish if a person has SMA or another type of neuromuscular disease.
What is spinal muscular atrophy?
Spinal muscular atrophy (SMA) is a genetic condition that results in weakness and wasting of muscles in infants. It also causes atrophy, where the muscles get smaller.
In SMA, the nerve cells in the brain and spinal cord break down. As a result, the brain can’t send a signal to the muscles to make them move, leading to muscular atrophy. SMA can affect the child’s ability to
- Crawl
- Walk
- Sit up
- Control head movements
Severe SMA can injure the muscles used for breathing and swallowing.
In most cases, SMA is caused by inadequate production of a protein called survival motor neuron (SMN) protein. Rarely, SMA is caused by mutations in other genes apart from SMN.
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