Researchers discovered that upper limb function progressively declined in patients with spinal muscular atrophy (SMA) types 2 and 3 over a 24-month period, according to a study published in Neuromuscular Disorders.

SMA causes progressive muscle weakness and atrophy; recently, attention has shifted towards quantifying these changes in the upper limbs. The Revised Upper Limb Module (RULM) was specifically developed to assess the upper limb function of patients with SMA, covering 19 items, from distal to proximal movements. 

Coratti et al decided to apply this scoring system to monitor the changes in upper limb function in patients with SMA type 2 (n=54) and type 3 (n=53) over a period of 24 months. The participants of this study did not receive any pharmacological treatments approved for SMA, such as risdiplam (Evrysdi®), nusinersen (Spinraza®), or onasemnogene abeparvovec (Zolgensma®).

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To qualify for this study, participants needed to be genetically diagnosed with SMA, be at least 5 years of age, and have completed 2 years of follow-up.

Read more about SMA etiology

“The overall RULM 24-month changes showed a mean decline of -0.79 points,” the research team said. This demonstrated that an overall progressive decline in upper limb function was clearly observed in patients with SMA over the course of the study period.

Using the RULM scoring system, most patients had mean changes within 2 points, either positively or negatively: only 23% of patients saw their score decrease by more than 2 points and 7% improved by more than 2 points. 

“In conclusion, our results in this population show slow progressive loss of RULM scores over 24 months, suggesting a progressive decline in upper limb function that becomes more obvious with increasing time,” Coratti and colleagues wrote.

The significance of this study is that it demonstrated a quantifiable way to monitor changes in motor function for patients with SMA.

“These findings can be of help at the time of selecting endpoints for future studies or for the interpretation of clinical trials and real-world data that are becoming increasingly available,” they concluded. 

Reference

Coratti G, Pera MC, Montes J, et al. Revised upper limb module in type II and III spinal muscular atrophy: 24 month changes. Neuromuscul Dis. Published online November 7, 2021. doi:10.1016/j.nmd.2021.10.009

Evrysdi Neurologists nusinersen Onasemnogene abeparvovec Orthopedists Pulmonologists risdiplam SMA type 2 SMA type 3 Spinraza Zolgensma