What is spinal muscular atrophy in children?

Spinal muscular atrophy (SMA) is a disease of the nerves and muscles caused by certain genes. It affects the motor neurons in the spinal cord. It causes muscle wasting and weakness.

What causes spinal muscular atrophy in a child?

SMA is caused by a faulty or missing gene called SMN1. SMA is an autosomal recessive disease. This means that all children are equally affected. And it means that one copy or missing copy of the faulty gene from each parent (2 total) are needed to cause the condition.

If both parents are carriers, they have a 1 in 4 chance for a child with SMA with each pregnancy. Carrier testing is usually done only if a child in the family is known to have SMA. In the U.S., newborns are now screened for the disease.

Which children are at risk for spinal muscular atrophy?

A child is more at risk for SMA if they have a parent or sibling with the disease.

What are the symptoms of spinal muscular atrophy in a child?

There are several types of SMA that affect children. They vary in the age when symptoms first appear, the seriousness of symptoms, and how symptoms get worse. Symptoms can also occur a bit differently in each child. The different types of SMA include:

• Type 0. This is the rarest and most severe type. It is found before a child is born. Newborns with this type may have joint or heart defects. They also have problems breathing. Many die within 6 months after birth.

• Type 1. This is also called Werdnig-Hoffman or infantile-onset SMA. This is a very severe type of SMA and may be present at birth. Infants have problems holding up their head, sucking, feeding, and swallowing. They tend to move very little. The muscles of the chest are also affected. The child moves their tongue in wormlike movements. Children with type 1 often die by age 2 because of breathing problems.

• Type 2. This is also called intermediate SMA. This form of SMA is seen in children from age 6 months to 18 months. Children with type 2 have overall muscle weakness. They may need braces, a walker, or a wheelchair. They can often live into adulthood.

• Type 3. This is also called Kugelberg-Welander or mild SMA. Symptoms may appear in children between ages 2 and 17 years. These children show signs of clumsiness, trouble walking, and mild muscle weakness. They may have delayed motor development. Children with type 3 live long into their adult years.

• Type 4. This form is uncommon and affects adults, typically in their 30s and 40s. It causes a walking disability.

The symptoms of SMA can be caused by other health conditions. Make sure your child sees a healthcare provider for a diagnosis.

How is spinal muscular atrophy diagnosed in a child?

SMA is sometimes hard to diagnose. The healthcare provider will ask about your child’s symptoms, past health, and your family’s health history. Your child will have a physical exam. Your child may also have tests, such as:

• Blood and saliva tests.  Babies may be screened for the condition shortly after birth. Older children may have tests that measure levels of a muscle enzyme. Genetic tests to check for conditions that tend to run in families are now a more common way to check for SMA.

• Muscle biopsy.  For this test, a healthcare provider removes a small sample of the muscle and checks it under a microscope. This is done rarely now that genetic tests are widely available.

• Electromyogram (EMG). This test measures the electrical activity of a muscle or a group of muscles. An EMG can show abnormal electrical muscle activity caused by conditions that affect the nerves and muscles.

How is spinal muscular atrophy treated in a child?

Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how bad the condition is.

There is no cure for SMA. The goals of treatment are to:

• Prevent breathing problems in children who have affected breathing muscles

• Give breathing support with a machine (ventilator) if needed

• Give nutritional support to children whose swallowing muscles are affected

These medicines can be used to treat SMA:

• Nusinersen. This medicine may help children with SMA achieve motor milestones that would not normally happen without treatment. It's injected into the cerebrospinal fluid.

• Onasemnogene abeparvovec. This medicine replaces the defective gene with a normal one. The gene is carried to the nerve cells by a benign virus.

• Risdiplam. This medicine helps nerve cells make more of the SMN protein. It's given by mouth.

Your child may be able to try other SMA treatments that are still being tested in clinical trials. Talk with your child’s healthcare provider to find out if there are any clinical trials you should consider.

Talk with your child’s providers about the risks, benefits, and possible side effects of all treatments.

What are possible complications of spinal muscular atrophy in a child?

Depending on the type of SMA, possible complications may include:

• Aspiration (when fluids or small bits of food get into the airways)

• Contractions of muscles and tendons

• Scoliosis, or curvature of the spine

• Trouble breathing due to muscle weakness and scoliosis

SMA has no cure. Treatment is supportive. It focuses on preventing complications of weakness. The severity of muscle weakness determines likelihood of survival.

How can I help prevent spinal muscular atrophy in a child?

Your healthcare provider may advise genetic counseling. You can discuss with a counselor the risk for SMA in a future pregnancy.

How can I help my child live with spinal muscular atrophy?

The healthcare team will talk with you about how to best care for your child at home. Consider talking to a medical social worker who is familiar with SMA to discuss the long-term care needs of your child, including health insurance coverage options. Children with SMA need regular visits with their healthcare providers.

Care for you and your family is also very important. Connect with support groups for help. Organizations, such as the Spinal Muscular Atrophy Foundation, can offer emotional support and helpful information to you and your family. Get counseling for yourself and family members to help deal with the ongoing stress.

When should I call my child’s healthcare provider?

Call the healthcare provider if:

• Your child has symptoms that don’t get better, or get worse

• Your child has new symptoms

• You have concerns about how to effectively care for your child at home

Key points about spinal muscular atrophy in children

• SMA is a disease of the nerves and muscles caused by certain genes. It affects the motor neurons in the spinal cord. It causes muscle wasting and weakness.

• SMA is caused by a faulty or missing gene. All children are equally affected. One copy or missing copy of the faulty gene from each parent (2 total) is needed to cause the condition.

• A child is more at risk for SMA if they have a parent or sibling with the disease.

• There are several types of SMA that affect children. They vary in the age when symptoms first appear, the seriousness of symptoms, and how symptoms get worse.

• SMA has no cure. One new treatment can result in improved motor function. The other goals of treatment are to treat breathing and nutrition problems.

• Your child may be able to try new SMA treatments that are still being tested in clinical trials. Talk with your child’s healthcare provider to find out if there are any clinical trials you should consider.

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:

• Know the reason for the visit and what you want to happen.

• Before your visit, write down questions you want answered.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.

• Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.

• Ask if your child’s condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if your child does not take the medicine or have the test or procedure.

• If your child has a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your child’s healthcare provider after office hours. This is important if your child becomes ill and you have questions or need advice.