Paeds Vivas · neurology-neurodisability-and-neuromuscular
Spinal muscular atrophy: Viva
Branching clinical structured oral on paediatric spinal muscular atrophy covering the SMN1 deletion genetics with the SMN2 copy number modifier and the exon 7 splicing defect, the five SMA types, the clinical picture of symmetric proximal hypotonia and areflexia with tongue fasciculations and spared intellect, the genetic diagnosis by homozygous SMN1 deletion, the three disease-modifying therapies nusinersen risdiplam and onasemnogene abeparvovec with their trial evidence, newborn screening and presymptomatic treatment, and the multidisciplinary care.
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Branch 1: Making the diagnosis
A strong candidate recognises this at once as type 1 spinal muscular atrophy. The discriminating pattern is the symmetric proximal weakness worse in the legs, the absent deep tendon reflexes, the tongue fasciculations, and the paradoxical breathing, all in a bright, socially engaged infant whose intellect is spared. The contrast between the alert face and the limp body is the signature clue, and it separates the spinal cause from the cerebral causes of hypotonia. The diagnosis is genetic and is made by a single blood test for the homozygous deletion of SMN1 exon 7, present in over ninety-five percent of affected individuals, which confirms the diagnosis in the right clinical picture. [1]
References7ShowHide
- [1]Mercuri E, Finkel RS, Muntoni F, et al Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis, rehabilitation, orthopedic and nutritional care. Neuromuscul Disord, 2018.PMID 29290580
- [2]Finkel RS, Mercuri E, Meyer OH, et al Diagnosis and management of spinal muscular atrophy: Part 2: Pulmonary and acute care; medications, supplements and immunizations; other organ systems; and ethics. Neuromuscul Disord, 2018.PMID 29305137
- [4]Finkel RS, Mercuri E, Darras BT, et al. Nusinersen versus Sham Control in Infantile-Onset Spinal Muscular Atrophy. N Engl J Med, 2017.PMID 29091570
- [6]Mendell JR, Al-Zaidy S, Shell R, et al Single-Dose Gene-Replacement Therapy for Spinal Muscular Atrophy. N Engl J Med, 2017.PMID 29091557
- [8]Baranello G, Darras BT, Day JW, et al. Risdiplam in Type 1 Spinal Muscular Atrophy. N Engl J Med, 2021.PMID 33626251
- [9]De Vivo DC, Bertini E, Swoboda KJ, et al. Nusinersen initiated in infants during the presymptomatic stage of spinal muscular atrophy: Interim efficacy and safety results from the Phase 2 NURTURE study. Neuromuscul Disord, 2019.PMID 31704158
- [11]Cooper K, Nalbant G, Sutton A, et al. Systematic Review of Presymptomatic Treatment for Spinal Muscular Atrophy. Int J Neonatal Screen, 2024.PMID 39189228