Over the past decade, three disease-modifying therapies (DMTs) for spinal muscular atrophy (SMA) have been approved in Canada: nusinersen (Spinraza) in June 2017, onasemnogene abeparvovec (Zolgensma) in December 2020 and risdiplam (Evrysdi) in April 2021. Although DMTs have transformed the treatment landscape for pediatric SMA patients, robust evidence supporting their effectiveness in adult populations remains limited. ^{Reference Hagenacker, Maggi and Coratti1,Reference Walter, Laforêt, van der Pol and Pegoraro2} Consequently, many adults with SMA (awSMA) in Canada lack access, as most provincial health plans do not cover these DMTs. ^{Reference Price, Hodgkinson and Westbury3} Those approved for therapy often face frequent clinical assessments for treatment renewal (e.g., every 4 months for nusinersen in Alberta), placing a significant burden on patients and families. ^{Reference Hodgkinson, Chapman and Izenberg4} A key barrier is the difficulty in capturing meaningful clinical change in awSMA, whose disease progression is often slower and more heterogeneous than in pediatric cases due to differences in SMN2 copy number, disease severity, motor function and systemic involvement. ^{Reference Vázquez-Costa, Povedano and Nascimiento-Osorio5}

Traditional outcome measures (OMs), many of which were developed and validated in children, may lack the sensitivity or relevance needed to detect subtle but important changes in adult function. ^{Reference Walter, Laforêt, van der Pol and Pegoraro2} The study by Slayter and colleagues offers a timely and clinically relevant evaluation of OMs used in awSMA, a population underrepresented in validation research. ^{Reference Slayter, Casey, Drost, McCullum, Christie and O’Connell6} Through a 12-month prospective evaluation of functional, motor and respiratory outcomes, the authors examine the performance of the consensus-derived SMA Recommended Toolkit in a small, mixed-treatment adult cohort. ^{Reference Slayter, Casey, Drost, McCullum, Christie and O’Connell6}

The study highlights key limitations in existing OMs for awSMA, noting that widely used tools like the SMAFRS and RULM lacked sensitivity to short-term clinical changes and showed considerable overlap – raising concerns about redundancy and inefficiency. ^{Reference Slayter, Casey, Drost, McCullum, Christie and O’Connell6} Only the CHOP-ATEND demonstrated strong sensitivity among non-sitters. ^{Reference Slayter, Casey, Drost, McCullum, Christie and O’Connell6} These findings underscore the need for targeted, validated, adult-specific tools that capture meaningful change across functional strata and reliably assess treatment response and disease trajectory in real-world settings. This has important implications for OMs selection in clinical and regulatory decision-making, especially when tied to accessing high-cost therapies. Less frequent clinical assessments reduce burden on SMA patients and healthcare resources. ^{Reference Hodgkinson, Chapman and Izenberg4}

Although the study does not resolve the optimal longitudinal OMs for treated versus untreated awSMA, it provides a foundation for future work. Meaningful progress in rare disease research often comes from the accumulation of small but rigorous studies like this one. Overall, Slayter and colleagues make a thoughtful contribution to the literature on OMs in adult neuromuscular populations and underscore the ongoing need for responsive, scalable tools that reflect clinically meaningful change.