As a healthcare professional, you are uniquely placed to spot whether a baby is developing as they should, whether this is at a routine check-up, or if parents or caregivers raise any concerns4

The SIGNS OF SMA

Select age range:

Very early signs of SMA are typically seen up to 6 months of age,1,2 often by age 3 months.2,5

Learn about the early signs to check for:

Hypotonia1,5

  • A baby with hypotonia is often described as ‘floppy’6 due to weakness in their arms and legs1,5
  • Symmetrical weakness that is more proximal than distal3 means that a baby will have difficulty lifting their arms and legs, but retain use of their hands and fingers6
  • The baby’s legs may seem weaker than their arms3
  • In profound cases, the baby may have a frog-like posture when lying1,7

Areflexia2

  • Absent or reduced deep tendon reflexes are characteristic of SMA1,2 and a critical part of the baby’s exam in cases of hypotonia7
  • Evaluation of deep tendon reflexes can be achieved by close monitoring of the baby’s response to brisk strikes of the tendon with a specialized hammer8

Head lag9

  • If a baby seems unable to lift their head or has poor head control,1,3,6 the pull-to-sit test can be used to confirm head lag10
  • A baby that is not developing typically will likely have their head lag behind their trunk, with their neck completely extended1,9,10,11
  • They may not lift their head above the line of their back when held horizontally face down7,8

Difficulty breathing5,6

  • Weakness of the intercostal muscles with sparing of the diaphragm can give the baby a bell-shaped chest and paradoxical pattern of breathing, sometimes referred to as ‘belly-breathing’1

Difficulty swallowing1,3

  • Difficulties with sucking, feeding, or managing oral secretions (saliva) can suggest tongue and swallowing weakness typical in SMA1,3,9
  • In more progressed cases, a history of choking, recurrent aspiration, or slow or reduced growth may be present1,6,9
Infant 0-6 months difficulty swallowing symptoms of spinal muscular atrophy (SMA) type 1

Tongue fasciculation1–3

  • A baby with SMA often will have tongue fasciculations, or twitching of the tongue, together with atrophy1–3

Weak CRY & COUGH3

  • A baby with SMA may have a weak cry3,6
  • Weakness of the respiratory muscles can also cause severe difficulties with coughing6

Babies with these signs remain alert, attentive and cognition is not affected1

Download the SMA Signs Watchlist

SMA SiGNS WATCHLIST

Early signs of SMA are typically seen up to 18 months of age,1 often by age 10 months;5

Learn about the early signs to check for:

Hypotonia1

  • Reduced muscle tone and strength on examination, perhaps with a history of poor muscle tone in the first few months of life is a key sign of SMA2
  • Some weakness in the arms and legs may be present1
  • The baby may have difficulty reaching for and picking up objects12
  • The baby is unable to stand due to pronounced leg weakness, and unlikely to walk independently1,3

Areflexia1,2

  • Absent or reduced deep tendon reflexes are characteristic of SMA2 and a critical part of the baby’s exam in cases of hypotonia7
  • Evaluation of deep tendon reflexes, can be achieved by close observation of the baby’s response to brisk strikes of the tendon with a specialized hammer8

Fine tremor3

  • When the baby extends their fingers or attempts to grip an object with their hands a fine tremor may be observed3,13
  • Twitching of their shoulder muscles may also be seen13
Infant 6-18 months fine tremor is a symptom of spinal muscular atrophy (SMA) type 2 and SMA type 3

Progressive scoliosis & Joint contractures1–3,14

  • Limited motion in the lower extremities, that is more severe than in the upper extremities is a sign of SMA15
  • The baby may show scoliosis, most likely C-shaped, and contractures, particularly of the knee and ankle, that continue to progress over time1–3,14,15
  • Pelvic obliquity, or pelvic tilt, may also be present14
Infant 6-18 month progressive scoliosis and joint contractures is a symptom of spinal muscular atrophy (SMA) type 2 and SMA type 3

Respiratory symptoms2

  • Restrictive lung disease can result from the progressive intercostal muscle weakness typical of SMA,2 particularly if the baby also has scoliosis1
  • Signs of restrictive lung disease include a reduced total lung capacity and forced vital capacity, with preserved expiratory volume16
Infant 6-18 months respiratory symptoms is a symptom of spinal muscular atrophy (SMA) type 2 and SMA type 3

Delayed/lost motor milestones2,3

  • Although the baby may have achieved early milestones (such as sitting or standing unsupported, and/or walking),1–3 it is likely they were delayed2
  • Eventually a gradual decline in motor function is observed and some milestones will be lost2
Delayed motor milestones in infant 6-18 months is a symptom of spinal muscular atrophy (SMA) type 2 and SMA type 3

Babies with these signs remain alert with normal speech development17

Download the SMA Signs Watchlist

SMA SiGNS WATCHLIST

Diagnostic delays are common in SMA5,20

Newborn screening programs for SMA are only just beginning to be implemented in a few countries across Europe21

If you suspect SMA in your patient, remember loss of motor neurons is irreversible; every day matters18,22,23

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Infantile nmd

SMA symptoms can overlap with other common infantile neuromuscular diseases (NMDs)24,25

NMDs typically manifest as; hypotonia, muscle weakness and areflexia24,25

Hypotonia is the most common reason for referral in children with NMDs25

SMA is one of the most common causes of hypotonia in infants26

NMDs affect multiple organ systems, and severe forms are debilitating and can affect life expectancy25

Common symptoms of NMD identified by parents:25

Hypotonia

Delayed motor milestones

Feeding and respiratory difficulties

Abnormal gait characteristics

Stiffness

Common pediatric NMDs:24

Spinal muscular atrophy

Duchenne muscular dystrophy

Becker muscular dystrophy

Congenital myopathy

Congenital muscular dystrophy

Myotonic dystrophy type 1

To distinguish between the different types of NMD and other conditions, genetic testing, alongside other tests and examinations, are key25

Download the differential diagnosis overview:

SMA DIFFERENTIAL DIAGNOSIS

References

References
  • 1. Kolb SJ and Kissel JT. Neurol Clin. 2015;33(4):831–46.
  • 2. Prior TW, Leach ME, Finanger E. Spinal Muscular Atrophy. 2000 Feb 24 [Updated 2019 Nov 14]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993–2020.
  • 3. Wang CH, et al. J Child Neurol. 2007;22(8):1027–49.
  • 4. Qian Y, et al. BMC Neurology. 2015;15:217.
  • 5. Pera MC, et al. PLoS One. 2020;15(3):e0230677.
  • 6. SMA Europe (2020). Type 1. Available at: https://www.sma-europe.eu/essentials/spinal-muscular-atrophy-sma/type-1/. Date accessed: October 2020.
  • 7. Leyenaar J, et al. Paediatr Child Health. 2005;10(7):397–400.
  • 8. Zimmerman B and Hubbard JB. Deep Tendon Reflexes (Stretch Reflexes) [Updated 2020 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan.
  • 9. Markowitz JA, et al. JOGNN. 2004;33:12–20.
  • 10. Great Ormond Street Hospital for Children NHS. Brief Developmental Assessment (BDA). Available at: http://www.gosh.nhs.uk/file/1841/download?token=oTvMwb9q. Date accessed: October 2020.
  • 11. Hammersmith Infant Neurological Examination (v07.07.17). Available at: https://bpna.org.uk/userfiles/HINE%20proforma_07_07_17.pdf. Date accessed: October 2020.
  • 12. Spinal Muscular Atrophy UK (2019). Toys and play for babies and children who have spinal muscular atrophy – A professional’s guide. Available at: https://smauk.org.uk/toys-and-play-a-guide-for-professionals. Date accessed: October 2020.
  • 13. SMA Europe (2020). Type 2. Available at: https://www.sma-europe.eu/essentials/spinal-muscular-atrophy-sma/type-2/. Date accessed: October 2020.
  • 14. Fujak A, et al. BMC Musculoskelet Disord. 2013 Oct 4;14:283.
  • 15. Wang HY, et al. Arch Phys Med Rehabil. 2004;85(10):1689–93.
  • 16. Martinez-Pitre PJ, Sabbula BR, Cascella M. Restrictive Lung Disease. [Updated 2020 Jul 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan.
  • 17. Shababi M, et al. J Anat. 2014;224(1):15–28.
  • 18. Govoni A, et al. Mol Neurobiol. 2018;55(8):6307–18.
  • 19. Mercuri E, et al. Neuromuscul Disord. 2018;28(2):103–15.
  • 20. Lin CW, et al. Pediatr Neurol. 2015;53(4):293–300.
  • 21. European Alliance for Newborn Screening in Spinal Muscular Atrophy (2020). Opening a new horizon for children born with SMA. Available at: https://www.sma-europe.eu/wp-content/uploads/2020/09/SMA-NBS-Alliance-pages-1.pdf. Date accessed: October 2020.
  • 22. Kirschner J, et al. Eur J Paediatr Neurol. 2020 Jul 9:S1090–3798(20)30142–2. Published online ahead of print.
  • 23. Glascock J, et al. J Neuromuscul Dis. 2018;5(2):145–58.
  • 24. Lee HN and Lee Y-M. J Genet Med. 2018;15(2):55–63.
  • 25. McDonald CM. Phys Med Rehabil Clin N Am. 2012;23(3):495–563.
  • 26. Lisi EC and Cohn RD. Dev Med Child Neurol. 2011;53(7):586–99.