The impact of Nusinersen treatment on scoliosis progression in patients with Spinal Muscular Atrophy

Objectives: Nusinersen treatment has improved motor function, ambulatory status and carers' satisfaction for spinal muscular atrophy patients. However its effect on scoliosis progression is unknown. The aim of this study was to examine the degree of scoliosis progression in SMA patients on Nusinersen.

Methods: 24 SMA patients with a minimum of 6 month follow up after commencement of Nusinersen treatment were recruited. Demographics, motor function, patient and carers' satisfaction were reviewed. Only patients with erect whole spine radiographs before and after treatment were included in analysis.

Results: 21 patients (Type 1=7, Type 2=9, Type III=5) were included in the analysis. The mean follow up was 29, 22 and 14 months respectively. Motor function was stable or improved in 18 patients. 57% of Type I patients became sitters (from 0%) and 33% of Type II patients became walkers (from 11%). Self or parent-reported improvements including stability and muscle strength were seen in all (100%) patients. However, scoliosis progression continued with a mean Cobb progression of 5.9, 12.4 and 2.6 degree per year for type I, II and III patients respectively. Sub-analysis of Type II patients showed that progression was most rapid (14.8 degree per year) between ages 5-10 years. This rate is similar to previously reported by Wikingarrde et al. (5-12 degree per year for Type II, and 2.9-15 degree per year for Type III).

Conclusion: Nusinersen treatment does not reduce the rate of scoliosis progression in SMA patients, and close monitoring with expectant surgical management is still required.