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Impaired Neurodevelopment in Children with 5q-SMA - 2 Years After Newborn Screening
Heike Kölbel1, Marius Kopka1, Laura Modler1
1Department of Pediatric Neurology, Centre for Neuromuscular Disorders, Center for Translational Neuro- and Behavioral Sciences, University Hospital Essen, Essen, Germany.
Insights
Children with Spinal Muscular Atrophy (SMA) and two SMN2 copies show impaired cognitive development, even with early therapy. This highlights the critical role of SMN protein in early brain development.
Area of Science:
- Neuroscience
- Genetics
- Pediatrics
Background:
- Reduced survival motor neuron (SMN) protein expression is characteristic of Spinal Muscular Atrophy (SMA).
- Previous studies show variable cognitive function in SMA patients, but cognitive development in those identified via newborn screening is less understood.
Purpose of the Study:
- To investigate the cognitive development of infants with SMA identified through newborn screening.
- To assess the impact of SMN2 gene copy number on cognitive outcomes in early-diagnosed SMA.
Main Methods:
- Developmental testing using the Bayley Scales of Infant and Toddler Development (Bayley III) was performed on 40 SMA patients (age 23-42 months) identified via newborn screening.
- Patients' SMN2 gene copy numbers were recorded (2, 3, or ≥4 copies).
Main Results:
- Cognitive scores averaged 94.55, language scores 86.09, and motor scores 81.28.
- 14 children scored below average cognitively, with 10 having 2 SMN2 copies.
- Cognitive scores were more sensitive to SMN2 copy number than motor scores.
Conclusions:
- Impaired cognitive development is observed in SMA children with 2 SMN2 copies, even with early treatment.
- These findings emphasize the crucial role of SMN protein in early brain development.
Objective:
Numerous studies have consistently found that reduced SMN protein expression does not severely affect cognitive function in SMA patients. However, the average intelligence quotient of SMA patients has ranged above to below average in different studies. The cognitive development of SMA patients identified through newborn screening remains largely unknown.
Methods:
40 of 47 eligible SMA patients (23 females/17 males) from 39 families identified through newborn screening between January 2018 and December 2020 underwent developmental testing using Bayley III (BSID) after the 2 years of age. The mean age was 29.25 months (23-42 months). 17 patients had 2, 11 patients had 3 and 12 patients had ≥4 copies of SMN2.
Results:
cognitive scale: mean 94.55 (SD 24.01); language scale: mean 86.09 (SD 26.41); motor scale: 81.28 (SD 28.07). Overall, the cognitive scales show that 14 children were below average, 20 children were average and 6 children were above average. 10/14 children with below average scores had 2 SMN2 copies. The post-hoc pairwise comparisons showed that the cognition main scale was significantly more sensitive to the number of SMN2 copies than the motor main scale of the BSID (MΔ= 10.27, p = 0.014). There is also evidence that cognition scored higher than the language main scale (MΔ= 7.11, p = 0.090).
Conclusion:
The impaired cognitive development of SMA children with 2 SMN2 copies, despite early initiation of therapy, underscores the critical role of the SMN protein in the early stages of brain development.
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