Spinal muscular atrophy (SMA) is an inherited neurodegenerative disorder characterized by progressive muscle weakness. Currently, no cure is available for SMA, but there are treatments that may help manage the condition. Several experimental therapies also are in development.

SMA patients do not produce enough of a protein called survival motor neuron (SMN), due to a mutation in the SMN1 gene. Another gene, SMN2, also can produce some SMN protein, but it is less stable. 

The type of treatments a patient needs depends on the severity of symptoms and should be determined by a team of healthcare professionals.

Disease-modifying therapies

Evrysdi

Evrysdi (risdiplam) is the first oral treatment for all types of SMA in patients 2 months and older. The U.S. Food and Drug Administration (FDA) approved it in August 2020. Roche and Genentech (a member of the Roche Group), who developed it in collaboration with PTC Therapeutics and the SMA Foundation, are marketing it.

Evrysdi is a small molecule that treats SMA by increasing the amount of functional SMN proteins. It allows a more stable form of the protein to be made from the SMN2 gene.

Spinraza

Spinraza (nusinersen), by Biogen, was the first disease-modifying therapy for SMA that the FDA approved in December 2016 to treat SMA in both infants and adults. The treatment also boosts the ability of the SMN2 gene to produce more functional SMN protein. 

Zolgensma

Zolgensma, a gene therapy developed by AveXis, a Novartis company, uses a genetically engineered virus to deliver a healthy copy of the SMN1 gene to the body to increase the levels of functional SMN protein. The FDA approved Zolgensma in 2019 to treat all types of SMA in patients up to age 2.

Other treatments

Other treatments that researchers have not specifically investigated in SMA may be beneficial to manage disease symptoms or prevent complications.

For example, muscle relaxants such as baclofen, tizanidine, and benzodiazepines can ease spasticity, when muscles become stiff and tense.

Jaw spasms, excessive saliva production, and the inability to swallow can cause drooling in SMA patients. Amitriptyline, Robinul (glycopyrrolate), or AtroPen (atropine) may address these issues.

Physical and occupational therapy

Physical therapy may help maintain muscle strength and range of motion for as long as possible in patients with SMA. However, incorrect or too much exercise may cause more harm than good, so patients need to discuss exercise plans with a physical therapist before starting to exercise. A physical therapist can help tailor an exercise program for the patient, monitor progress, and change the program as necessary.

An occupational therapist can recommend specialized assistive equipment that may help some patients maintain their independence. These include braces for the arms and legs, orthotics (shoe inserts to improve walking ability), speech synthesizers, and wheelchairs.

Breathing aids

SMA weakens the muscles between the ribs that help the chest expand so air can enter the lungs during breathing. As a result, patients rely solely on the diaphragm for breathing, which is not very effective and causes difficulties. This weakness can worsen as other muscles also deteriorate with time.

Patients may require ventilation to support breathing if they cannot get enough oxygen into their bodies. Depending on the severity of symptoms, these aids can be either non-invasive or invasive. Non-invasive ventilation is usually a short-term solution where a mask covering the mouth delivers oxygen to the patient. Invasive ventilation involves a tube either inserted down the trachea from the mouth, or surgically inserted through a small incision in the neck for long-term ventilation.

Nutritional treatments

Chewing and swallowing can be difficult if the jaw and throat muscles have deteriorated. As a result, patients may struggle to get enough nutrition, which can cause weight loss and affect growth in children. Other issues may include aspiration, when food or liquid goes down the windpipe and causes lung infections.

Gastroesophageal reflux disease also can be a problem when the muscle between the food pipe (esophagus) and stomach weakens and allows stomach acid to travel back up the food pipe.

A carefully regulated diet may be effective in managing nutritional problems. However, in more severe cases, patients may need aids such as feeding tubes. This involves a tube being passed through the nose or mouth into the stomach, or the surgical insertion of a tube through the abdomen and into the stomach. The nutrients, balanced for the needs of the patient, then can be delivered directly into the stomach via these feeding tubes.

Scoliosis treatments

Patients with SMA sometimes develop scoliosis — an abnormally curved spine. If spotted early, a special brace for the back may be able to encourage the spine to develop correctly. However, if this does not work, surgery may be necessary to straighten the spine.

 

Last updated: Aug. 11, 2020

***

SMA News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.