Spinal Muscular Atrophy

What is spinal muscular atrophy?

Spinal muscular atrophy (SMA) is a genetic, progressive disease that causes the loss of nerve cells, called motor neurons, in the brain and spinal cord. These nerve cells control muscles throughout the body. When the nerve cells are not working properly, it can lead to weakness in the muscles that control the arms, legs, chest, face, tongue and throat.

Symptoms of SMA can range from mild to life-threatening, depending on the type:

• SMA type 1 (also called infantile-onset SMA or Werdnig-Hoffmann disease) is the most severe type of SMA. Children with this type usually begin showing signs of the disease in the first few months of life. They have trouble moving their head, are not able to sit up, and have trouble feeding and breathing.
• SMA type 2 is not as severe as type 1. Children with type 2 usually develop symptoms between ages 6 and 12 months. While children with this type can often sit up, they are not able to stand or walk on their own.
• SMA type 3 (also called Kugelberg-Welander disease) is a milder type of SMA. Children may not develop symptoms until early childhood. They can usually stand and walk, but as the symptoms worsen, they may need to use a wheelchair.
• SMA type 4 is a rare form of the disease. A child with this type may not have any symptoms until they are a young adult. This type may cause muscle weakness, tremors and some mild breathing problems.

Although there is no cure for SMA, new treatments have given hope to children with the most severe types of SMA and their families.

What are the symptoms of spinal muscular atrophy?

The symptoms of SMA and their severity can vary depending on the type your child has. Some common symptoms in children include:

• Muscle weakness
• Low muscle tone
• Feeding and swallowing problems
• Trouble breathing
• A curve in the spine (scoliosis)
• Trouble sitting up or standing
• Trouble walking or running
• Tremors

What causes spinal muscular atrophy?

SMA is caused by a mutation or deletion in the SMN1 gene. In nearly all cases of SMA, the mutation is inherited from both parents.

How is spinal muscular atrophy treated?

Although there is no cure for SMA, new treatments provide hope for children with the most severe forms of this disease. Your care team at Arkansas Children’s is experienced in treating SMA and will work with you to create the best treatment plan for your child based on their individual symptoms.

• Nusinersen (brand name Spinraza) was the first FDA-approved drug to treat children and adults with SMA. Arkansas Children’s was the first medical center in Arkansas to offer this treatment. Spinraza may be effective at slowing, stopping or reversing the symptoms of SMA.
• Risdiplam (Evrysdi) is another FDA-approved drug for SMA. It is used to treat patients ages 2 months and older.
• Onasemnogene abeparovec-xioi (Zolgensma) is a type of gene therapy for SMA. It is used to treat SMA in children under age 2.
• Physical and occupational therapy may help slow muscle weakness and improve range of motion.