Association of Phosphorylated Neurofilament Heavy Chain (pNF-H) Levels With Motor Function Achievement in Individuals With Spinal Muscular Atrophy (SMA) Treated With Nusinersen (S27.009)

To assess phosphorylated neurofilament heavy chain (pNF-H) levels in individuals from nusinersen clinical trials with presymptomatic (most likely to develop Type I/II), infantile-onset (has or most likely to develop Type I/II) or later-onset SMA (has or most likely to develop Type II/III) and volunteers without SMA and investigate the association with motor function (MF) achievement in nusinersen-treated individuals with SMA.