Electrophysiological Changes in Pediatric Spinal Muscular Atrophy: Results From an Observational Study

Area of Science:

• Neurology
• Pediatric Medicine
• Clinical Electrophysiology

Background:

• Spinal muscular atrophy (SMA) affects motor nerves, with limited characterization of lower-limb and proximal nerves.
• Previous research primarily focused on upper-limb nerves in pediatric SMA patients.

Purpose of the Study:

• To evaluate compound muscle action potential (CMAP) amplitudes in upper- and lower-limb motor nerves in children with SMA.
• To assess changes in CMAP amplitudes following nusinersen treatment.

Main Methods:

• Retrospective analysis of CMAP amplitudes in 47 children with SMA (types 1-3) and 63 age-matched controls.
• Cross-sectional assessment of tibial, peroneal, femoral, median, and ulnar nerve CMAP amplitudes before treatment.
• Longitudinal evaluation of CMAP changes after 18 months of nusinersen-based therapies.

Main Results:

• Children with SMA exhibited significantly reduced CMAP amplitudes across all assessed nerves compared to controls.
• CMAP amplitudes correlated with SMA disease severity, being highest in type 3 and lowest in type 1.
• Significant increases in peroneal, femoral, median, and ulnar nerve CMAP amplitudes were observed after 18 months of nusinersen treatment.

Conclusions:

• CMAP amplitudes effectively differentiate SMA disease severity in pediatric patients.
• Nusinersen treatment is associated with improvements in CMAP amplitudes.
• Further large-scale longitudinal studies are needed to validate CMAP amplitude as a biomarker for SMA treatment response.