<p>Long-term motor functioning in spinal muscular atrophy (SMA) is a key focus, particularly in adult patients, as disease progression, muscle fatigue, and functional decline can persist despite treatment. At <strong>Cure SMA 2025</strong>, several presentations highlighted innovative approaches to assessing long-term motor function in individuals with SMA.</p> <p><br></p> <p><em>Following these presentations, featured expert Brian D. Snyder, MD, PhD, was interviewed by </em>Conference Reporter<em> Associate Editor-in-Chief Mona Shah, PharmD. Clinical perspectives from Dr Snyder on these findings are presented here.</em></p>

The fastest-growing population of patients with SMA is adults who were diagnosed late. Disease-modifying therapies are administered very late in the game in this group of patients, so the therapeutic benefits are going to be less profound than they would be in patients who were diagnosed as young children. The adult group of patients with SMA is heterogeneous, with a predominance of nonsitters and sitters as opposed to walkers. This reflects the natural history of the disease, and most of the population will have a higher number of copies of the SMN2 rescue gene because the patients with fewer copies of this gene often die at an early age from complications associated with SMA, predominantly pulmonary complications. As adults with SMA who were diagnosed late are the fastest-growing population of patients with this disease, we are trying to develop new methods for tracking changes in their functionality.

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Tina Duong, MPT, PhD, presented data at Cure SMA 2025 from a prospective study evaluating long-term motor responses to disease-modifying therapies in adults with SMA. This is an interesting study because it examined trends in outcome metrics using a large longitudinal collection of data that allows you to look at both the natural history of the disease and the treatment response. What I think is really interesting about this work is that the investigators were able to establish the minimal clinically significant differences in these outcomes that you must use to be able to say that treatment is having any effect at all. They showed that there was a progressive decrease in many of these outcome variables over time. What they did not do was explain why some of these things happen. So, that is the next stage, but I think that this is a nice study that helps us start to answer the question, “What is the threshold that you have to change to be able to say whether treatment is effective or not?”

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Another presentation at Cure SMA 2025 by Carly Mueller, PT, DPT, PCS, looked at gait speed in SMA as a sign linked to strength and fatigability. They used instrumented insoles to calculate stride length, step length, gait speeds, and stride velocity as a way of measuring the displacement over time. It is really interesting that they looked at gait speed reserves, which is calculated from how much faster you can go when told to speed up. It is a nice way to assess the reserve capability and fatigability of a muscle. I think that, potentially, this could become a metric to look at when assessing walkers to determine whether you are making a difference in the muscle itself.

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Finally, at Cure SMA 2025, there were a couple of studies by Jason J. Howard, MD, and his group at Nemours Children’s Health on the new Spinal Muscular Atrophy Functional Classification System (SMAFCS; abstracts 70 and 71). They developed a grading system based on the Functional Mobility Scale (FMS) and the Hammersmith Functional Motor Scale Expanded (HFMSE). This new grading system was found to be sensitive to factors such as a patient possibly losing some functionality, going from being independent to being more dependent, due to puberty and weight loss. Having a classification system such as this that could be applied without having to go through the rigors of the HFMSE would give us a quick and easy way to communicate patients’ functional capabilities. I think that this is quite neat and very pragmatic.