Spinal muscular atrophy (SMA) is treated with a combination of disease-modifying drugs and supportive care tailored to the patient’s age, disease severity, and functional ability. Three FDA-approved therapies now exist that target the root cause of SMA: insufficient production of a protein essential for motor nerve survival. Alongside these drugs, respiratory support, nutritional management, and orthopedic care play critical roles in maintaining quality of life.
Why Treatment Timing Matters
SMA is caused by a mutation in the SMN1 gene, which leaves the body unable to produce enough of a protein that keeps motor neurons alive. Without this protein, the nerve cells that control muscles gradually die, leading to progressive weakness. All three approved treatments work by either boosting this protein’s production or replacing the faulty gene entirely, so the earlier they’re given, the more motor neurons they can protect before damage becomes irreversible.
The evidence on early treatment is striking. In clinical trials of presymptomatic infants (identified through newborn screening before symptoms appeared), 100% of babies treated with gene therapy achieved independent sitting, 79% could stand on their own, and 64% walked independently. By contrast, among infants already showing symptoms of the most severe form, 49% achieved sitting with support and 82% reached motor milestones that would never occur without treatment. Comparative studies consistently show that presymptomatic treatment leads to better outcomes than treatment started after symptoms appear, which is why newborn screening programs have become so important.
Gene Therapy: A One-Time Infusion
The gene therapy for SMA delivers a working copy of the SMN1 gene directly into a child’s cells using a harmless virus as a carrier. It’s given as a single intravenous infusion, meaning one treatment is intended to last a lifetime. This therapy is approved for children under 2 years of age with confirmed genetic mutations, and the child must weigh between about 2.6 and 21 kilograms at the time of infusion. Premature infants need to reach their full-term gestational age before receiving it, because the required steroid medication given alongside the infusion could affect neurological development in preterm babies.
Real-world data from a study of 343 children across Germany, Austria, and Switzerland confirmed that the treatment’s effects hold up over time, with sustained benefits at a median follow-up of over five years. Both children treated before symptoms appeared and those treated after symptom onset maintained their gains, and the safety profile remained favorable across a range of ages and weights.
Spinal Injections Every Four Months
The first drug approved for SMA, nusinersen, works differently. Rather than replacing the missing gene, it helps a backup gene (SMN2) produce more functional protein. It’s delivered through a lumbar puncture, a needle inserted into the fluid surrounding the spinal cord. The initial phase involves four loading doses: the first three given two weeks apart, with the fourth dose 30 days after the third. After that, maintenance injections continue once every four months, indefinitely.
This treatment is approved for all ages and all types of SMA, making it an option for older children and adults who aren’t eligible for gene therapy. The repeated spinal injections can be uncomfortable, and some patients with scoliosis or spinal fusion hardware may need imaging guidance to ensure accurate needle placement. Despite these challenges, the treatment has shown meaningful improvements in motor function across clinical trials involving both infants and later-onset patients.
A Daily Oral Medication
Risdiplam is a liquid taken by mouth once a day. Like nusinersen, it boosts protein production from the backup SMN2 gene, but it works throughout the entire body rather than just in the spinal fluid. It’s approved for patients 2 months of age and older, with no upper age limit, making it the most broadly accessible of the three treatments.
Dosing is weight-based for younger or smaller patients: children under 2 receive 0.2 mg per kilogram of body weight daily, those 2 and older weighing under 20 kg receive 0.25 mg/kg, and anyone 20 kg or above takes a flat 5 mg dose. Because it’s a liquid that can be given at home with no needles or hospital visits, many families find it the most practical option for long-term daily use. It can also be administered through a feeding tube for patients who have difficulty swallowing.
Choosing Between Treatments
The choice among these three therapies depends on a child’s age, weight, disease type, and family preferences. Gene therapy is a one-time option but only available to children under 2. Nusinersen requires ongoing spinal injections but has the longest track record and broadest age approval. Risdiplam offers the convenience of daily oral dosing at home. In some cases, clinicians use combination approaches, such as gene therapy followed by an oral or injectable treatment, though guidelines on combination use are still evolving.
Breathing Support
Weakness in the muscles that control breathing is one of the most serious complications of SMA, particularly in its more severe forms. Proactive respiratory care has been shown to extend survival and reduce hospitalizations. The two main tools are a bilevel positive airway pressure (BiPAP) machine, typically worn during sleep to help keep the airways open, and a mechanical cough assist device, which helps clear mucus from the lungs by simulating a natural cough.
For infants with SMA type 1, proactive care often starts within the first three months of diagnosis, with BiPAP used during all sleep periods and cough assist performed at least twice daily. This approach represents a significant shift from older supportive strategies that relied mainly on supplemental oxygen and suctioning, which addressed symptoms but didn’t prevent the underlying airway problems. Some children with severe respiratory involvement eventually need a tracheostomy for long-term ventilation, though the newer disease-modifying drugs have reduced how often this becomes necessary.
Nutrition and Feeding
Swallowing difficulties are common in SMA, especially in types 1 and 2. When oral feeding becomes unsafe or insufficient (due to aspiration risk or the sheer effort of eating), a gastrostomy tube (G-tube) is often placed. This small tube, inserted through the abdomen directly into the stomach, allows nutrition and medications to be delivered without relying on impaired swallowing. For many families, a G-tube reduces stress around mealtimes and helps ensure consistent calorie intake, which is important because children with SMA are prone to both undernutrition and, in less mobile patients, excess weight gain.
Orthopedic Management
Scoliosis, or curvature of the spine, develops in the majority of children with SMA types 1 and 2 because the muscles supporting the spine are too weak to hold it straight during growth. Bracing can help manage mild curves and improve sitting posture in younger children, but progressive curves typically require surgical correction. Spinal fusion, the standard procedure for severe scoliosis, is usually performed around age 12 to 13, when patients are close to skeletal maturity. The surgery stabilizes the spine and can improve breathing mechanics by preventing the ribcage from being compressed by a worsening curve.
Hip dislocations and joint contractures (where joints become stiff in a fixed position) are also common. Physical therapy, stretching programs, and sometimes bracing help maintain range of motion and comfort. Regular standing, whether independently or with a standing frame, supports bone density and joint health even in children who cannot walk.
Physical Therapy and Rehabilitation
Regardless of which drug treatment a patient receives, ongoing physical and occupational therapy remains a cornerstone of SMA care. Therapy focuses on maintaining the range of motion that exists, strengthening muscles that still function, and adapting activities so patients can participate as fully as possible in daily life. For children, this often means working on sitting balance, hand function, and mobility with adaptive equipment like power wheelchairs. For adults with milder forms, therapy may center on preserving walking ability, managing fatigue, and adapting workspaces. Aquatic therapy is particularly popular because the buoyancy of water allows movements that gravity makes difficult on land.