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Signs and symptoms of SMA

Spinal muscular atrophy (SMA) is a single-gene disease with a spectrum of clinical presentation according to age of onset and severity, which makes diagnosis difficult1,2

patient
patient

Clinical presentation for SMA may differ according to the age of onset and severity, but hypotonia (floppy baby syndrome) and/or muscle weakness and atrophy are common signs or symptoms:1

  • Weakness is usually symmetrical
  • Weakness is more proximal than distal
  • Sensation is preserved
  • Tendon reflexes are absent or diminished
  • Weakness is greater in the legs than the arms
  • Severity of weakness generally correlates with the age of onset
table
table

Time to diagnosis is critical – earlier diagnosis and intervention may help improve the outcomes for individuals with SMA.1

Download the red flags checklist

Common complaints from parents of
children with suspected neuromuscular
disorders such as SMA may include:1

  • Delays in motor milestones
  • Feeding and respiratory difficulties
  • Abnormal gait characteristics
  • Frequent falls
  • Difficulty ascending stairs or arising from the floor
  • Muscle cramps or stiffness
  • Loss of strength, fatigue, or decreasing endurance
  • Exercise intolerance; episodic weakness
  • Muscle cramps and focal wasting of muscle groups
  • Breathing difficulties or bulbar symptoms relating to speech and swallowing

In the adult patient, a detailed history may help point to a diagnosis, including:7

  • Pattern of progression of symptoms
  • Age at onset of symptoms
  • Age at which bracing was provided to maintain ambulation
  • Age at which wheelchair was required (if applicable)
  • Distribution of weakness
  • Presence of muscle cramps
  • Fatigue; episodic weakness
  • Presence of atrophy or fasciculations
  • Current and past ambulatory distances
  • Ability to transition from floor to standing
  • Problems climbing stairs, reaching overhead, or dressing

If you see symptoms of SMA in your patient, refer immediately for an urgent appointment with a paediatric neurologist.

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References
  1. Prior TW and Finanger E. Spinal muscular atrophy. NCBI Bookshelf Web site. http://www.ncbi.nlm.nih.gov/books/NBK1352/report =printable. Updated December 22, 2016. Accessed October 2017.
  2. Wang CH et al. J Child Neurol 2007; 22: 1027–49.
  3. Darras BT et al. Neuromuscular Disorders of Infancy, Childhood, and Adolescence: A Clinician’s Approach. 2nd ed. London, UK: Elsevier; 2015.
  4. Lunn MR and Wang CH. Lancet 2008; 371: 2120–33.
  5. NIH National Center for Advancing Translational Sciences. Genetic and Rare Diseases Information Center. Spinal muscular atrophy type 2. https://rarediseases.info.nih.gov/diseases/4945/spinal-muscular-atrophy-type-2. Accessed October 2017.
  6. Rothwell E et al. Am J Med Genet A 2013; 161A: 679–86.
  7. McDonald CM. Phys Med Rehabil Clin N Am 2012: 23: 495–563.