Healthdirect Australia is not responsible for the content and advertising on the external website you are now entering.
Spinal muscular atrophy (SMA)
6-minute read
Key facts
- Spinal muscular atrophy (SMA) is a genetic condition.
- SMA causes muscles to become weaker and smaller over time.
- There are 5 different types of SMA.
- Cognition and intelligence are not affected by SMA.
- Although there is no cure for spinal muscular atrophy, there are new treatments available.
What is spinal muscular atrophy?
Spinal muscular atrophy (SMA) is a genetic condition. It affects the nerves that control your muscles. These nerves are known as motor neurons.
Over time, these muscles become weaker and start to atrophy (get smaller).
SMA can affect the muscles used for:
- moving your arms, legs and head
- breathing, coughing and swallowing
While there is no cure for SMA, there are treatments to help with symptoms, and slow the condition from getting worse.
SMA is a childhood form of motor neurone disease.
Types of spinal muscular atrophy
There are 5 types of SMA. These are based on the age when symptoms first appear.
- Type 0 — symptoms are present from birth.
- Type 1 — symptoms usually develop during the first 6 months of life.
- Type 2 — symptoms usually appear between 6 to 18 months of age.
- Type 3 — symptoms usually appear after 18 months of age.
- Type 4 — symptoms usually appear from early adulthood.
Type 1 SMA is the most common type.
What are the symptoms of spinal muscular atrophy?
The symptoms of SMA depend on its type. Type 0 SMA is the most severe form, and type 4 SMA is the mildest.
Type 0 spinal muscular atrophy
Type 0 SMA is the most severe form and affects babies in the womb.
Symptoms include:
Unfortunately, babies born with type 0 SMA usually don't survive more than 2 months.
Type 1 spinal muscular atrophy
Type 1 SMA is also called Werdnig-Hoffman disease. The symptoms include:
- weak muscle tone
- difficulty sitting on their own
- poor head control
- a weak cry and cough
- difficulty swallowing
Currently, babies with type 1 SMA usually do not live past their second birthday.
Type 2 spinal muscular atrophy
Children with type 2 SMA may:
- not reach their motor (movement) milestones on time
- have a weak cough
- have fine hand tremors
- have joint contractures (stiff joints that won't straighten)
- have scoliosis (curving of the spine)
Type 2 SMA may shorten life expectancy, but many children live into adulthood. People with type 2 SMA often can't stand or walk on their own.
Type 3 spinal muscular atrophy
Type 3 SMA is also known as Kugelberg–Welander disease. Symptoms can include:
- muscle weakness and cramps
- joint contractures
- loss of the ability to walk
People with type 3 SMA have a normal life expectancy.
Type 4 spinal muscular atrophy
People with type 4 may have mild to moderate muscle weakness and tremors.
People with Type 4 SMA have a normal life expectancy.
What causes spinal muscular atrophy?
SMA is a genetic condition.
It is a recessive disorder. This means that you need to inherit a copy of the faulty gene from both of your parents.
As many as 1 in 50 people in Australia have a faulty SMA gene. SMA affects people from all ethnic groups.
When should I see my doctor?
See your doctor if you have concerns about your child's:
- muscle tone — they may seem floppy
- difficulty lifting their head up
- difficulty during 'tummy time'
- 'froglike' position when lying
Read more on low muscle tone in babies and toddlers.
FIND A HEALTH SERVICE — The Service Finder can help you find doctors, pharmacies, hospitals and other health services.
How is spinal muscular atrophy diagnosed?
Your doctor will examine your child. They may recommend genetic testing which looks at a gene called SMN1 or SMN2. Other tests may also be done to rule out other conditions.
All Australian-born babies can be tested for SMA a few days after birth. This is usually through a few drops of blood from your baby's heel. If this test is positive, other tests can help confirm a diagnosis.
ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.
How is spinal muscular atrophy treated?
There is currently no cure for SMA, but there are medicines that can stop SMA from getting worse and help with symptoms.
Medicines can slow the progression of some types of SMA. While they don't cure the disease, they help stop further decline.
Nusinersen is a medicine that is injected into the fluid that surrounds the spine a few times a year. Risdiplam is a medicine you take by mouth (orally) every day.
The long-term effects of these treatments aren't yet known.
Living with spinal muscular atrophy
A team of healthcare professionals with different types of expertise will help you manage SMA. These professionals may include:
- a neurology specialist (nervous system doctor)
- a respiratory specialist (breathing doctor)
- an orthopaedic specialist (bone doctor)
- an occupational therapist
- a physiotherapist
Management goals will depend on your current symptoms.
What are the complications of spinal muscular atrophy?
SMA can lead to serious complications, including trouble with breathing, swallowing, and muscle strength loss as nerve cells deteriorate. Some types of SMA are fatal (cause death).
SMA is a physical condition and does not affect your intelligence.
Can spinal muscular atrophy be prevented?
While SMA can't be prevented, carrier testing can help parents know the chances of passing it on to their children. Medicare covers the costs of reproductive carrier testing. You may have this test:
These tests help you make informed choices about having children by better understanding the chance your baby will be born with SMA.
Newborns with SMA can start treatment before symptoms appear. This can improve their symptoms and help them survive.
Resources and support
For more information and support, visit Spinal Muscular Atrophy Australia.
You may also be interested in learning more about the Australian Neuromuscular Disease Registry (ANMDR). The ANMDR collects information from patients to improve the understanding of neuromuscular disease.
You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.
Find an Aboriginal Community Controlled Health Organisation (ACCHO) or Affiliate near you.
Languages other than English
Health WA has brochures on newborn screening tests available in several community languages.
Parent Line is a free telephone counselling and support service for parents and carers. They offer parenting support for parents from culturally diverse backgrounds.