Patient Guide to Spinal Muscular Atrophy

Adult Spinal Muscular Atrophy: Treatment

Hearing you have a genetic disease like spinal muscular atrophy type 4 can be jarring, but it’s important to know that new treatments and some lifestyle modifications can help you live your life to the fullest.

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You might have mixed feelings if your doctor tells you that you have a genetic disease like spinal muscular atrophy (SMA). On one hand, you’re probably relieved to finally have a diagnosis, one that could have been a long time coming. You can stop wondering about why you’ve never really been that athletic or why your balance seems to be deteriorating lately. Mystery solved.

Woman being treated for adult spinal muscular atrophy (type 4)New treatments for adult spinal muscular atrophy (type 4) can slow disease progression and help you live your life.

On the other hand, there’s trepidation. SMA type 4? Never heard of it, let alone know anyone else with it. What will the future hold? Will this kill me? Can I get treated?

Last questions first: No, it won’t kill you—not type 4—and yes, you can get treated.

Why Do I Have SMA Type 4?

If you have SMA, your SMN1 gene is either missing or mutated. SMN1 provides the instructions for the creation of SMN protein, which maintains the motor neurons necessary for proper muscle function. Your body then relies on another gene, SMN2, to create SMN protein. But SMN2 can’t make enough of it, which means you won’t have adequate motor neurons; as a result, you’ll grow progressively weaker. The more copies of the SMN2 gene you have, the later the onset and the less severe your condition will be.

There are multiple types of SMA, characterized by the number of SMN2 copies you have. The earlier your symptoms appear, the more severe your case. SMA type 4 is the latest onset and least severe form of SMA, and is characterized by weakness that generally starts in your legs and finger tremors.

While it can progress to the point where it interferes with your breathing, mobility, and activities of daily living (ADLs), many people with SMA 4 maintain the ability to walk independently throughout their lifespan.  The sooner you receive a diagnosis and begin treatment, the better your prognosis. 

Diagnosing SMA 4

The mildest of all forms of SMA, type 4 can be difficult to diagnose. According to Wildon Farwell, MD, MPH, Global Medical Head of Neuromuscular Diseases at Biogen, over two-thirds of all babies born in the United States are tested for SMA at birth.

SMA 4, which is typically diagnosed in your 20’s, 30’s, or 40’s, often involves “a long diagnostic journey,” says Dr. Farwell. While the hallmark signs of SMA 4 include proximal weakness that starts in the legs and finger tremors, these symptoms don’t necessarily lead providers to consider SMA immediately. When patients report less overall stamina, increasing falls, and just generally feeling weaker and slower, “this often results in evaluation which then can be diagnosed as SMA,” says Dr. Farwell.

Unfortunately, explains Thomas Crawford, MD, it can take years to get a diagnosis. By then, you’ve lost valuable motor neurons—and physical function—that are impossible to restore. Since treatment prevents further muscular degeneration, early diagnosis is key to a good prognosis.

To make an accurate diagnosis, you will undergo genetic testing.

SMA treatment has exploded recently, creating a much brighter future for those affected by the disease. Although gene therapy treats the most severe forms of SMA in the youngest, most vulnerable patients, new medicines can help those diagnosed later in life, and lifestyle changes can help you live to the fullest no matter the state of your SMA’s progression.

Drug Therapies

In 2016, nusinersen (Spinraza) was the first drug FDA-approved for SMA treatment. Since then, gene therapy (Zolgensma) and another medication, risdiplam (Evrysdi), have also been approved. Both nusinersen and risdiplam increase the SMN2 gene’s capacity for SMN protein synthesis.

Nusineren (Spinraza)
Nusinersen is approved for use for those ages two months and older. It’s given via a spinal tap, an injection in your lower back. After receiving four initial “loading doses” in your first two months of treatment, you’ll receive another injection every four months for the rest of your life.

The drug works by helping the SMN2 gene to make more SMN protein.

According to a 2019 study, the most common side effects were respiratory tract infections and constipation. Other issues included breathing difficulties, pneumonia, and increased needs for respiratory support.

Overall, Dr. Crawford calls it “exceptionally safe” and says the most risky aspect is drug administration. Because SMA can cause spinal deformities, some patients require interventional radiology for accurate needle placement. He says there are plans to develop a port that can be placed at the injection site, which would eliminate the need for repeated injections.

Risidiplam (Evrysdi)

Risidiplam is approved as an SMA medication for those who are two months old and up. It’s taken orally (by mouth) at the same time every day and must be refrigerated. It was FDA approved in August 2020, making it the newest SMA treatment available at the time of this writing.

Like nusinersen, it also helps the SMN2 gene create more SMN protein.

Potential side effects include fever, diarrhea, rash, upper respiratory tract infection, pneumonia, constipation, and vomiting. According to Dr. Crawford, animal testing elicited “some concern about gonadal issues, with testes and ovaries.” As the newest SMA medication, the medical community is still learning about risidiplam’s side effects.

Gene Therapy (Zolgensma)

Gene therapy is approved for patients under two years old. Administered by IV, it works by injecting copies of working SMN1 genes directly into the body. Once in the bloodstream, the new SMN1 genes find the motor neurons and instruct them to make SMN protein.


Physical, occupational, and speech therapy can help people with SMA optimize their independence and endurance for mobility and ADLs. Physical and occupational therapy in particular can help with contracture management, using modalities such as passive stretching and splinting.

Therapies may offer tools such as adaptive equipment—like a shower chair or utensils with built-up handles—to maximize your functional abilities. Additionally, they’ll teach you strategies such as energy conservation techniques to empower you to budget your energy.

With any rehab program, it’s important to listen to your body, says Dr. Crawford. Your rehab routine shouldn’t exhaust you to the point where you’re too fatigued to participate in everyday activities. “It’s not always the case that more is better,” he explains. Rather than focusing on an exercise routine, rehab goals should focus on function. “The purpose of PT is to be able to live a life.”

One of the most important steps people with SMA 4 can take to maximize their quality of life is to advocate for themselves. Speaking up and asking questions may help you obtain a speedier diagnosis, resulting in earlier treatment and, ultimately, a better prognosis. It’s also important to keep your family informed of your needs so they know how to help, says Dr. Farwell.

Once you have a diagnosis, Dr. Farwell encourages open communication with your care team. He suggests working with a neuromuscular specialist who is connected to a multidisciplinary clinic where you have access to physical therapy, pulmonary support, and more. Given the recent breakthroughs in SMA treatment, “It’s hard to keep up with all the new data coming out,” he says, which is why it’s key to have “frequent conversations with [your] team to understand the latest data on each of the therapies.”


Updated on: 02/26/21
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Khoi D. Than, MD
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