Motor function and compound muscle action potential amplitude in children with spinal muscular atrophy treated with nusinersen.

Background: Disease-modifying therapies can improve motor function in patients with spinal muscular atrophy (SMA), but efficacy varies between individuals. The aim was to evaluate the efficacy and safety of nusinersen treatment in children with SMA and to investigate prognostic factors.

Methods: Motor function, compound muscle action potential (CMAP), and other indicators were prospectively collected before and 14 months after nusinersen treatment.

Results: A total of 55 children were included in our study to assess safety. 41 patients (with at least 6 months of nusinersen treatment) were included in the final efficacy analyses, with a median age at first treatment of 4.2 years. After 14 months of treatment with nusinersen, motor function improved, with increases in CHOP INTEND (Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders), HINE-2 (Hammersmith Infant Neurological Exam-Part 2), HFMSE (Hammersmith Functional Motor Scale-Expanded) and RULM (Revised Upper Limb Module) of 5.5 (95 % CI -2.4-13.4), 0.8 (95 % CI -0.2-1.9), 5.0 (95 % CI 2.5-7.4) and 2.4 (95 % CI 0.7-4.1) points, respectively. The CMAP amplitudes of the bilateral tibial, median and ulnar nerves increased, with greatest improvements of 0.87 ± 1.41 mV, 1.08 ± 1.71 mV and 0.59 ± 1.01 mV, respectively. Spearman correlation analysis showed that age at first treatment, disease duration, joint contractures and scoliosis were associated with treatment efficacy (r = -0.4-0.7, P < 0.05). Subgroup analyses showed that the mean HFMSE and RULM scores improved in the Physical therapy group (P < 0.05).

Conclusion: Early treatment, mild bone and joint complications, and regular rehabilitation training were associated with better outcomes. The other motor-related functions, such as respiratory and bullar function, and prognostic factors should be studied in the future.