Spinal Muscular Atrophy
The survival rate for children with SMA type 1 is about 7 years old with a mortality rate of 95 percent by 18 months old.

Spinal muscular atrophy (SMA) is a hereditary disorder characterized by progressive muscle weakening and atrophy (when the muscles get smaller). Children with SMA may find it difficult to crawl, walk, sit, or control head motions. SMA can affect the muscles that control breathing and swallowing, causing serious complications.

SMA is divided into four types. Some types appear earlier and with greater severity than others. All types of SMA require extensive medical care from a medical team. The condition has no cure, but treatment can help children live better lives. People with SMA and their parents can have their genetics tested to see how likely they are to have another child with SMA.

  • The median survival rate for people with SMA type I is about seven months, with a mortality rate of 95 percent by 18 months of age.
    • The majority of deaths are caused by respiratory diseases.
  • The age at which patients with SMA type II die varies although respiratory difficulties are the most common cause of death.

Care of children with SMA benefits from a multidisciplinary approach. Parents, doctors, nurses, therapists, counselors, and dietitians are among the members of the team. The chances for children with SMA have improved as a result of this method, which has been combined with recent medical improvements.

What happens in spinal muscular atrophy?

Spinal muscular atrophy affects the nerves that control muscular strength and movement. These nerves are found in the spinal cord and lower section of the brain (known as motor neurons). When SMA strikes, the nerves are unable to transmit impulses from the brain to muscles. In the absence of nerve signals, the muscle cells shrivel and ultimately degenerate.

What causes spinal muscular atrophy?

A mutation in the SMN1 gene is responsible for the majority of instances of spinal muscular atrophy (SMA). A protein necessary for proper motor neuron activity is not produced in sufficient amounts by this gene. Motor neurons perish and are, thus, unable to transmit muscular impulses.

A child with SMA receives one copy of the SMN1 gene from each parent. A child who inherits the SMN1 gene from only one parent is unlikely to develop SMA although they may pass it on to their children.

4 types of spinal muscular atrophy

Based on the severity of the disease and the age at which symptoms first show, spinal muscular atrophy (SMA) is categorized into four groups.

  1. Type I: Also known as Werdnig–Hoffmann disease or infantile-onset SMA, this is the most common and severe type. It affects infants from birth to six months of age, with the majority of babies showing symptoms by three months.
  2. Type II: Affects children who are between 7 and 18 months of age. Children can sit but not walk on their own. This type can range in severity from modest to severe.
  3. Type III: Commonly known as Kugelberg–Welander syndrome or juvenile SMA, this affects children from 18 months of age to adolescence. Although children can walk on their own, their arms and legs are weak, and they are prone to falling. This is the mildest form of SMA in youngsters.
  4. Type IV: The adult type of SMA with symptoms commonly appearing after 35 years of age and gradually worsening over time.

What are the signs and symptoms of spinal muscular atrophy?

Spinal muscular atrophy (SMA) can show up in various ways. Some newborns with SMA are “floppy,” meaning they don't learn to roll or sit when they should. An older child may fall more frequently or have more difficulties lifting objects than a younger child.

If the back muscles are weak, scoliosis (a curved spine) can occur in children with SMA. A child with severe SMA may be unable to stand or walk, and eating and breathing may require assistance.

How is spinal muscular atrophy diagnosed?

Spinal muscular atrophy (SMA) is diagnosed in various ways.

Doctors may conduct the following tests if they suspect a kid has SMA:

  • Genetic testing: The most prevalent method of detecting SMA is where the SMN1 gene is tested for a deletion or variant.
  • Biopsy: Doctors take a small sample of the muscle to examine it under a microscope.

What is the treatment of spinal muscular atrophy?

Although there is no cure for spinal muscular atrophy (SMA), the following treatments can help children with the condition:

  • Nusinersen (also known as SpinrazaTM):
    • A novel SMA treatment was authorized in 2016.
    • This medication increases the quantity of protein produced by the SMN1 gene that is deficient in the body.
    • It works by the production of the SMN2 gene that acts as a backup, looks more like the SMN1 gene, and creates the required protein.
    • A spinal tap is used to administer this medicine.
    • Four doses are given over two months, followed by four doses every four months after that.
    • According to studies, breathing, motor function, and survival all improved significantly after administering this medication.
  • Trials of gene therapy:
    • These are ongoing and have proved to improve overall function in patients with SMA.
  • Supportive treatments:
    • A mask/mouthpiece or breathing machine can help with breathing. Tracheostomy may be required (a tube is surgically inserted into the trachea to help in breathing)
    • Treatments to help children clear mucus that can aid in the prevention of illnesses and adequate nutrition. Feeding tubes may be used
    • Scoliosis can be managed with medication, splint, brace, or surgery
    • Physical and occupational therapy
    • Support groups and counseling

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Medically Reviewed on 10/27/2021
Image Source: iStock Images