We acknowledge some limitations of the study, including the absence of CSF samples from healthy controls and untreated SMA patients, the relatively small sample size within each SMA subtype, the lack of an assay of widely used biomarkers such as NfL to parallel the results obtained, and the limited follow-up period of 10 months, that may constrain the robustness of the conclusions. This evidence concerns the gene NEFL and proximal spinal muscular atrophy.