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DIAGNOSING SMA

IN CHILDREN

Based on the natural history of the disease, earlier diagnosis could lead to improved outcomes for children with SMA. This makes time to diagnosis critical, even though newborn screening is not yet standard practice.1

The characters shown are real patients and the required consent to use their stories has been obtained from the patients and families. Photographs are for illustrative purposes only.

SMA IS AN AUTOSOMAL RECESSIVE GENETIC DISEASE2,3

Spinal muscular atrophy (SMA) is a single-gene disease with a spectrum of clinical presentation, differing according to the age of onset and severity.4,5 Hypotonia (floppy baby syndrome) and/or muscle weakness and atrophy are common signs or symptoms in children.5,6

However, children with spinal muscular atrophy are often noted at diagnosis to have a bright, alert expression that contrasts with their general weakness.3

Learn about Signs and Symptoms of SMA:

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A GENETIC DISORDER

A child inherits two deleted or mutated SMN1 genes – one from each parent.7

Learn more about Biology and Genetics of SMA here

THE IMPORTANCE OF EARLY DIAGNOSIS

The natural progression of SMA involves irreversible loss of motor function.8 Following an initial increase, a peak in motor skills and subsequent downturn marks the onset of SMA, with disease progression (and loss of motor skills) being most rapid in the early stage.8

Early diagnosis may be an important consideration in the treatment of SMA.9

The pattern of motor neuron loss seen in SMA suggests that a treatment for infantile-onset (Type 1) SMA should be administered as early as possible, including the pre-symptomatic period before significant loss of motor neurons.9

Molecular genetic testing is an important tool in the diagnosis of SMA.5,10

EVALUATING THE TYPES OF SMA

Several motor function scales have been developed that are useful in quantifying the natural history of SMA, as well as the response to investigational therapeutic agents in clinical trials.11-13

1.

The Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND)

The CHOP INTEND test is used to evaluate the motor skills of infants with SMA and to assess SMA Type 1 patients who have limited motor skills.11,14

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2.

Hammersmith infant neurological examination (HINE)

HINE is a simple motor function assessment tool designed to evaluate motor skills in infants from 2 months to 2 years of age.12

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3.

Hammersmith Functional Motor Scale—Expanded (HFMSE)

HFMSE is a validated measure that has been used in several clinical trials to evaluate the motor function of children with SMA.13,15

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The characters shown are real patients and the required consent to use their stories has been obtained from the patients and families. Photographs are for illustrative purposes only.

References

1. Rothwell E, Anderson RA, Swoboda KJ, Stark L, Botkin JR. Public attitudes regarding a pilot study of newborn screening for spinal muscular atrophy. Am J Med Genet A 2013;161A(4):679-686.

2. Lunn MR, Wang CH. Spinal muscular atrophy. Lancet 2008;371(9630):21‌20-21‌33.

3. Darras BT, Royden Jones H Jr, Ryan MM, De Vivo DC, eds. Neuromuscular Disorders of Infancy, Childhood, and Adolescence: A Clinician’s Approach. 2nd ed. London, UK: Elsevier; 2015.

4. Prior TW, Russman BS. Spinal muscular atrophy. NCBI Bookshelf Web site. [online] 2019 Nov [Cited 2020 Oct 15]. Available from: URL: http://www.ncbi.nlm.nih.gov/books/NBK1352/?report=printable.

5. Mercuri E, et al. Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis, rehabilitation, orthopedic and nutritional care. Neuromuscl Disord 2018;28(2):103-115.

6. MedlinePlus. Spinal muscular atrophy. [online] 2019 [cited 2021 Mar 1]. Available from: URL: https://medlineplus.gov/ency/article/000996.html.

7. National Organization for Rare Diseases. Spinal muscular atrophy. [online] 2012 [cited 2016 Apr 17]. Available from: URL: http://rarediseases.org/rarediseases/spinal-muscular-atrophy/.

8. Swoboda KJ, et al. Perspectives on Clinical Trials in Spinal Muscular Atrophy. J Child Neurol. 2007;22:957-66.

9. Finkel RS. Electrophysiological and motor function scale association in a pre-symptomatic infant with spinal muscular atrophy type I. Neuromuscul Disord 2013;23(2):112-115.

10. D'Amico A, Mercuri E, Tiziano FD, Bertini E. Spinal muscular atrophy. Orphanet J Rare Dis. 2011;6:71.

11. Glanzman AM, et al. The Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND): test development and reliability. Neuromuscul Disord 2010;20(3):155-161.

12. Romeo DM, Ricci D, Brogna C, Mercuri E. Use of the Hammersmith Infant Neurological Examination in infants with cerebral palsy: a critical review of the literature. Dev Med Child Neurol 2016;58(3):240-245.

13. Mercuri E, et al. Patterns of disease progression in type 2 and 3 SMA: implications for clinical trials. Neuromuscul Disord 2016;26(2):123-131.

14. Spinal Muscular Atrophy Clinical Research Center. CHOP INTEND for SMA Type I score sheet. [online] 2013 Mar [cited 2016 Apr 26]. Available from: URL: http://columbiasma.org/docs/cme-2010/CHOP%20INTEND%20for%20SMA%20Type%20I%20-%20Manual%20of%20Procedures.pdf.

15. The Pediatric Neuromuscular Clinical Research Network for SMA. Expanded Hammersmith Functional Motor Scale for SMA (HFMSE). [online] 2009 Mar [cited 2016 Apr 25]. Available from: URL: http://columbiasma.org/docs/HFMSE_2019_Manual.pdf.