Until very recently, treatments for spinal muscular atrophy (SMA) could only manage symptoms. Existing therapies supported breathing, eating, and mobility functions as muscle weakness inevitably progressed. In the past few years, new treatment options to modify the course of the disease have become available for people with most types of SMA.
Depending on age, SMA type, and the severity of SMA symptoms, people with SMA may require different types of treatment throughout their lives.
Spinraza (nusinersen), the first disease-modifying therapy for SMA, was approved by the U.S. Food and Drug Administration (FDA) in 2016. A second disease-modifying therapy, Zolgensma (onasemnogene abeparvovec-xioi), became available in 2019. Clinical trials to test new treatments for SMA are ongoing.
Both Spinraza and Zolgensma are types of gene therapy. Zolgensma, which is indicated for infants under the age of 2, is administered as a one-time intravenous infusion. Zolgensma is believed to work by modifying the faulty survival motor neuron 1 (SMN1) gene. In people with SMA, the SMN1 gene underproduces survival motor neuron (SMN) protein, which is critical to motor function.
Spinraza is given intrathecally — injected into the spinal canal through which the spinal cord passes – once every four months after the first few loading doses. Spinraza is believed to work by increasing the production of SMN protein by a similar “backup” gene, the SMN2 gene. Spinraza is recommended for most infants with SMA as well as children between ages 2 and 12.
Side effects of both Spinraza and Zolgensma can include abnormal bleeding and vomiting. Zolgensma may cause serious liver injury in some people. Spinraza may cause kidney problems, constipation, headache, fever, and lower respiratory infections.
In some people with SMA, the respiratory muscles weaken, and breathing becomes difficult. Respiratory issues are the most common cause of illness and the most common cause of death for children with SMA type 1 (Werdnig-Hoffmann disease) and SMA type 2. Ventilation assistance can significantly extend life in people with SMA who have breathing problems. There are many types of assisted ventilation systems.
Many doctors advise starting with noninvasive ventilation support. Noninvasive ventilation devices can be used as needed and easily removed for talking or eating. A noninvasive ventilation system involves an airtight mask worn over the nose or nose and mouth. The mask is connected to a machine that delivers air under pressure. The air may or may not be enriched with oxygen. One form of noninvasive ventilation is a bilevel positive airway pressure (BiPAP) machine, which may be used for breathing support when someone with SMA is sleeping or during sickness. A sipper vent is a mouthpiece positioned like a microphone when someone with SMA is sitting in a wheelchair. The sipper vent can make it easier to talk and breathe at the same time.
If noninvasive ventilation is not sufficient to support breathing, invasive ventilation support may be considered. Unlike a noninvasive ventilation system, an invasive ventilation device will penetrate the body. An endotracheal tube, which is placed in the mouth and goes down the trachea and into the lungs, may be used for a few days or weeks before causing irritation. If invasive ventilation support is needed for an extended period of time, the doctor may recommend creating a tracheostomy — a small, surgical hole in the throat — to place a breathing tube directly into the trachea. Many people with a tracheostomy can learn to eat, drink, and talk normally.
In cases where scoliosis (abnormal curvature of the spine) is compromising breathing and lung development, a vertical expandable prosthetic titanium rib (VEPTR) may be implanted. The surgically implanted device attaches to the ribs, and sometimes the spine or hips, and helps straighten the spine and separate the ribs to create space. The VEPTR device is expandable as the child grows. A VEPTR is usually implanted before age 5.
Weak respiratory muscles can also make it difficult for people with SMA to cough and effectively clear mucus from the lungs. Many forms of respiratory therapy can help with this issue. Chest physiotherapy, also called manual or mechanical percussion, involves gently clapping on the chest wall (or using a vibrating device) to loosen mucus. Postural drainage involves placing the child on an incline, with head lowered, to encourage mucus to move upward. An insufflator-exsufflator device, such as the CoughAssist, provides pressure on the airway to produce a coughing effect. A high-frequency chest wall oscillation device, such as the InCourage, comes in the form of a vest that creates vibrations to help move mucus.
In some people with SMA, the muscles involved in chewing and swallowing become weak. When these muscles weaken, it becomes difficult to eat and increases the risk for aspiration (inhaling food particles into the lungs). It may become necessary to use a feeding tube system that bypasses the mouth and esophagus.
There are many types of feeding tubes. A gastric or gastrostomy tube (G-tube) is one of the most common types of feeding tubes. G-tubes are placed surgically through the skin and into the stomach. A nasogastric (NG) tube is introduced through the nose and placed into the stomach, while nasoduodenal (ND) and nasojejunal (NJ) tubes enter the nose and empty into the small intestine.
Liquid nutrition for tube feedings may be purchased commercially or made at home. People with feeding tubes may still eat by mouth for pleasure, if the risk of aspiration is not too great.
A speech-language pathologist (SLP) can help overcome problems with speech and swallowing that develop due to weakness in the tongue, throat, and respiratory muscles. An SLP may teach strategies for safer swallowing, conserving breath while speaking, or using adaptive language techniques if communication becomes difficult.
Physical therapy (PT) can help people with SMA maximize their function, strength, and endurance. After an evaluation to assess goals and needs, a physical therapist may focus on strengthening exercises, energy conservation techniques, fall prevention, or getting the best use out of mobility aids. For people with severe SMA, PT can improve positioning, determine better bracing to prevent contractures (permanent shortening of a muscle or joint), and address range of motion. For children with SMA, PT can help them set and work toward goals of mobility and independence and delay the onset of complications.
Occupational therapy focuses on increasing independence in activities of daily living, whether in the home, at work, or in school. For instance, an occupational therapist may address fatigue while typing on a keyboard.
Nearly all children with SMA develop scoliosis. There are many different approaches to treating scoliosis. Some doctors recommend using braces to improve quality of life and delay scoliosis surgery. Scoliosis is progressive in most cases and can lead to the development of problems with breathing and other functions. For these reasons, scoliosis surgery is generally recommended after age 10, or when children have finished growing. There are several options for the correction of scoliosis. Surgeries include spinal fusion and the implantation of growing rods or a VEPTR device. Doctors may recommend a combination of these approaches to best address scoliosis.
There is no specific diet that is recommended for everyone with SMA, nor is there evidence that any diet can help treat SMA. However, people with SMA may have some specific nutritional needs. While fasting over many hours, our bodies break down muscle for glucose. Since muscle is lost in SMA, this can pose a nutritional strain on the body. For this reason, people with SMA may benefit from a diet high in protein and complex carbohydrates such as whole grains, lentils, and root vegetables. Some doctors recommend individuals with SMA take nutritional supplements such as creatinine or coenzyme Q10.
To limit long fasting periods, frequent smaller meals may be preferable to a few large meals. Difficulty chewing and swallowing are common symptoms of SMA. Changing the consistency of food can help make it easier to eat and lower the risk for aspiration.
It is crucial for babies and small children with SMA to get enough nutrients and calories for brain growth and development. A nutritionist familiar with SMA can help by creating a nutrition plan that adapts as the child’s nutritional needs change.
Older children and adults with SMA may need to control how many calories they take in, since a lack of effective exercise can lead to weight gain. Always talk to your doctor before making changes to diet — some special diets may be harmful for a person with SMA, and certain nutritional supplements may cause dangerous interactions with medications.
Physicians have differing opinions on the role of exercise for people with SMA. Most doctors recommend exercising as much as feels comfortable for optimal physical and psychological health. Exercise may help protect the joints from injury, preserve range of motion, and support healthy blood circulation. However, some doctors worry that too much exercise may speed the progression of muscle loss in SMA. More research is needed to better understand how much exercise is beneficial in SMA.
People with SMA are particularly prone to respiratory infections. It is recommended to get a flu vaccination each year to help avoid infection. It may also be beneficial to avoid large gatherings where exposure to infection is likely.