Characterizing Perceived Physical Fatigability in Nusinersen-treated SMA

Inclusion Criteria: 1. All types of 5qSMA (homozygous deletion or point mutation of the SMN1 gene and any number of SMN2 copies) 2. Receiving a stable dosing regimen of 12 or 28 mg nusinersen for at least 6 months Exclusion Criteria: 1. An injury or surgery within the previous 3 months that would impact their ability to perform in-clinic function and/or fatigability assessments 2. Enrolled in an ongoing clinical trial, or extension study, expanded access program, or long-term registry of an investigational or recently approved medication 3. Receiving adjuvant and/or dual therapy (e.g., muscle-targeted, NMJ, or symptomatic treatments)