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Spinal Muscular Atrophy (SMA)

At a glance

Approximate incidence in Ontario: Marker measured: Screening can prevent: Treatment:
1 in 10,000 Deletions in SMN1 gene, SMN2 gene copy numbers Muscle weakness and motor delays, death Medications: physical, respiratory, and other supportive therapies

In Ontario, every baby has a few drops of blood taken from their heel when they are about a day old.  The blood is tested for more than 25 treatable diseases, including one called spinal muscular atrophy (SMA).

Screening for SMA started in mid-January 2020 as a pilot program and the end of July 2020, SMA was officially added to the newborn screening panel in Ontario. 

screen positive result means that the baby most likely has a type of SMA and more tests are needed to be sure. Screening is important because babies with SMA can be healthier if they are identified and treated early.

  • Spinal muscular atrophy (SMA) is a rare inherited (genetic) disease that results in muscle weakness and muscle wasting (atrophy) throughout the body.
  • There are 4 main types of SMA depending upon the age that symptoms start to show and by the highest level of motor skills (e.g. sitting, crawling, walking) that a baby or child is able to achieve:
    • Type 1: babies are weak and not able to sit up by themselves. Symptoms start to show up in the first 6 months of life
    • Type 2: children can sit by themselves by do not walk. Symptoms start to show up between 6-18 months of age
    • Type 3: children can walk and sit by themselves but start having muscle weakness and muscle wasting in childhood, after 18 months of age.
    • Type 4: symptoms of this type of SMA appear in adulthood
  • Newborn screening for SMA detects SMA type 1 and 2, most cases of type 3, and some cases of type 4.

  • screen positive result means that the baby most likely has a type of SMA and more testing is needed to be sure.   
  • It is natural for parents and guardians to feel worried and have questions when their baby has a screen positive result.
  • A health care provider at a newborn screening regional treatment centre or the baby’s healthcare provider will discuss the screening results with the baby’s family.
  • Follow-up testing is arranged as soon as possible and usually involves blood tests and an assessment with a pediatric neurologist (a doctor who specializes in disorders that affect the nerves, spinal cord and brain in children).
  • It can take a few days to confirm that a baby has SMA. This waiting period can be hard for families. 

  • Abnormal – the baby has a form of SMA and should get care from a pediatric neurologist. The pediatric neurologist, along with other specialists, will discuss what follow-up is best for the baby.
  • Normal – the follow-up test results show that the baby does not have a form of SMA. This would be an unexpected result and more testing may be recommended.
  • Inconclusive – sometimes the results can show that the baby has SMA but it is unclear which type of SMA the baby may develop. The family will be supported by a neurologist who will make sure that appropriate follow-up and monitoring takes place.

Babies with SMA usually do not have any symptoms at birth. Symptoms appear typically in the first few weeks of life for SMA type 1.  Early signs may include:

  • Low muscle tone (hypotonia)
  • Muscle weakness and muscle wasting that gets worse over time (e.g. poor head control)
  • Loss of reflexes
  • Uncontrolled movements of the tongue (fasciculations)
  • Tremor
  • Feeding and swallowing difficulties, poor weight gain (failure to thrive)
  • Abnormal/rapid breathing patterns

The main goal of screening is to help find children who have SMA earlier. Children with SMA can benefit from being identified early and getting treatment sooner.

Your baby’s pediatric neurologist and healthcare team will discuss management and treatment options available to your child.

Treatment is available for babies with SMA who have 1, 2 or 3 copies of the SMN2 gene. Babies with 3 or less copies are expected to have SMA type 1, 2 or 3.

In Ontario, a medication called Nusinersen (Spinraza) is approved for treatment of patients with SMA who have 3 or less copies of the SMN2 gene. 

  • If started early, Nusinersen can stop the progression of SMA.
  • Nusinersen is provided in a hospital by a physician and is given through a spinal tap (lumbar puncture).
  • Treatment is lifelong and begins with 6 treatments in the first year of life. After the first year, treatment is given 3 times each year.

Without treatment, the more severe, early onset forms of SMA (type 1 in particular) will lead to death in the first year or two of life. 

Gene therapy (Zolgensma) is being developed but is not yet approved for use in Canada. It may be available on a compassionate basis through Global Access Program, however this cannot be guaranteed.

Babies with 4 or more copies of the SMN2 gene will be checked regularly for symptoms of SMA. Babies with 4 or more copies of the SMN2 gene are expected to have SMA type 3 or type 4, but some babies may develop type 2. If symptoms develop, your child’s doctor will discuss treatment options.

When treatment starts early, the chance to achieve the highest level of motor skills possible is better.

If your baby has screened positive for SMA, click here for more information.

Contact Us

Children’s Hospital of Eastern Ontario
415 Smyth Road
Ottawa, Ontario K1H 8M8

Toll-Free: 1-877-627-8330
Local: (613) 738-3222
Fax: (613) 738-0853

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