Spinal Muscular Atrophy: Causes, Treatments & Symptoms

What Is Spinal Muscular Atrophy (SMA)?

Spinal muscular atrophy, also known as SMA, is a genetic disorder that affects the part of the nervous system that controls our ability to move our muscles voluntarily. Children with spinal muscular atrophy need care from experts in several medical fields.

This disease affects the major nerves coming out of the spinal cord called motor neurons, causing the muscles they control to weaken and get smaller. It is caused by the loss of both copies, from the mother and father, of the SMN1 gene. Individuals with SMA must rely on the SMN2 gene (a backup copy) to provide the important SMN protein.

However, this gene can only produce about 10% of the full-length protein that the motor neurons need. There are now treatments that target both of these genes (SMN1 and SMN2) to make more SMN protein to improve the health of the motor neurons in those with SMA. This diagnosis can have a wide range of presentations with different ages of onset, symptoms and rates of progression.

The Spinal Muscular Atrophy Program at CHRISTUS Children's brings together a team of experienced specialists in caring for children with this rare and complex condition. Dr. Melissa Svoboda, who specializes in neurology, leads the team at CHRISTUS Children's

Spinal Muscular Atrophy Treatment Options

The Food and Drug Administration (FDA) has approved three treatment opportunities for patients with Spinal Muscular Atrophy. These treatments include Nusinersen (Spinraza), Risdiplam (Evrysdi), and onasemnogene abeparvovec-xioi (Zolgensma). Which treatment is used depends on many factors. Speak with your pediatric neurologist to decide which treatment is best for your child.

Spinraza – FDA approved in the US for all ages, infants through adulthood. Spinraza is given intrathecally (via a needle in the back directly into the spinal fluid) approximately every 4 months. However, 4 “bolus” injections or loading doses are required more frequently at the start of therapy every 2-4 weeks. It works by increasing the amount of SMN protein using an antisense oligonucleotide (ASO). For more information see: https://www.spinraza.com/

Evrysdi – FDA approved in the US for ages 2 months and older. Evrysdi is a DAILY oral (or G-tube) medication given at home every single day to treat SMA. It works by increasing the amount of SMN protein using a SMN2 splicing modifier. For more information see: https://www.evrysdi.com/

Zolgensma – FDA approved in the US for ages 2 years and younger. Zolgensma is a gene therapy given ONCE through an IV infusion. It requires a minimum of 3 months of frequent lab monitoring after infusion. It works by inserting the SMN1 gene into cells via a viral vector called adeno-associated virus 9 (AAV9). Then, the cells will be able to make their own functional SMN protein using the new SMN1 gene. For more information see: https://www.zolgensma.com/

Gene Therapy Breakthrough for Spinal Muscular Atrophy Patients

The FDA approved Zolgensma in 2019 as a one-dose gene therapy for children under 2 years old with SMA. Zolgensma is designed to replace the survival motor neuron (SMN1) gene. It is as close to a cure as we can get.