Spinal muscular atrophy (SMA) is an inherited genetic neuromuscular disorder that causes muscle weakness. SMA is caused by a mutation in the SMN1 gene, leading to the degeneration of motor neurons (nerve cells responsible for movement) in the spinal cord. Sometimes, scoliosis occurs in infants or children with SMA. Scoliosis is a sideways curvature of the spine and, in SMA, it commonly occurs as a result of muscle weakness. There are several treatment options for scoliosis.

What Is Scoliosis?

Neuromuscular scoliosis is different from idiopathic scoliosis — in idiopathic scoliosis, the cause is uncertain or unknown. On the other hand, effectively controlled neuromuscular scoliosis is a common deformity of the spinal cord that occurs as a result of many neuromuscular disorders, including SMA.

Scoliosis is progressive. In other words, the spine curvature occurs gradually as the child grows, although scoliosis can get worse even after the child stops growing. The natural progression of scoliosis can cause lung capacity and movement problems, which can contribute to some of the symptoms of SMA.

What Does Scoliosis in SMA Look and Feel Like?

Scoliosis commonly occurs in children with SMA. It can develop in SMA type 1, type 2, and type 3. Research suggests that children with SMA 2 develop scoliosis most often compared to the other types. Spinal deformities can also occur in other forms, known as kyphosis (a backward or hunchback curve of the spine) or lordosis (a forward curve of the spine). According to the SMA Foundation, approximately one-third of people with scoliosis in SMA have kyphosis, lordosis, or a pelvic tilt combined with their scoliosis.

Scoliosis in SMA is also associated with breathing problems and reduced mobility. As the spinal cord curves, it changes the shape of the back. This change affects how much room the lungs have to expand. When the lungs can’t expand enough, respiratory distress (problems breathing that decrease oxygen supply to organs) can occur. Mobility is also negatively affected, and scoliosis increases the stiffness of the hip joints. The pelvis can also be affected, becoming uneven and rotated to one side (called pelvic obliquity). All of these effects together can make scoliosis a painful component of SMA.

What Causes Scoliosis in SMA?

Scoliosis in SMA is a result of muscle weakness around the spine. This muscle weakness is due to the genetics underlying SMA. The primary cause of SMA is a mutation or deletion in the SMN1 gene, the gene responsible for producing survival motor neuron (SMN) protein. SMN protein plays an essential role in the health of nerves at the base of the brainstem and in the spinal cord. When a person doesn’t make enough of this protein, their nerve cells die and their muscles weaken or atrophy (waste away). When the weakened muscles can’t support the spine, scoliosis can occur.

Treating Scoliosis in SMA

There are several options for treating scoliosis in people with SMA. Although bracing is possible, spinal surgery is the most common treatment for scoliosis caused by SMA. According to the SMA Foundation, there is controversy in the field of orthopedics about whether bracing has an effect on slowing spine curve progression. There are, however, a few options for scoliosis surgery, and advances in techniques for spine surgery have helped increase the quality of life in people with scoliosis and SMA.

Spinal Fusion Surgery

Spinal fusion surgery is one option for surgical treatment. This procedure involves fusing spinal vertebrae, eliminating movement between the vertebrae. Usually, a piece of bone is inserted into the space, although sometimes plastics or metals can be used. In one study, children who underwent spinal fusion surgery were about 10 years old, on average. Although these children were still growing, spinal fusion surgery effectively controlled spine curvature progression and pelvic obliquity even at a 10-year follow-up (post-surgery).

Growing Rods

Growing rods are expandable devices anchored at both the top and bottom of the spine using hooks and screws. Research shows that growing rods are an effective way of treating scoliosis in children with SMA who have few complications. Additionally, growing rods allow the spine to continue growing, whereas the spine can’t keep growing after spinal fusion surgery.

A newer method known as magnetically controlled growing rods has also been shown to be an effective treatment option, improving quality of life, increasing mobility, and reducing the psychological distress associated with undergoing multiple surgeries.

Building a Community

The social network mySMAteam is for people with spinal muscular atrophy and their loved ones. On mySMAteam, members come together to ask questions, share advice and experiences, and make connections with people around the world who understand life with SMA.

Have you experienced scoliosis with SMA? Share your experience in the comments below, or start a conversation by posting on mySMAteam.