However, this may be the case if one considers that impaired proprioception is also associated with an altered muscle spindle morphology, which is indeed documented here for the first time in SMA III, confirming what previously described in both ALS and SMA I (Kararizou et al. 2006; Limanaqi et al. 2017; Kröger and Watkins 2021). Here, SMN1 is linked to amyotrophic lateral sclerosis.