Table 1

Study inclusion and exclusion criteria for participants in the study

Inclusion criteria	Exclusion criteria
Genetically confirmed homozygous SMN1 deletions	Children who were beyond >4 months since commencement of treatment, that is, those who had already transitioned to nusinersen maintenance treatment at the start of the study
Clinical signs and symptoms consistent with a diagnosis of SMA	Children with comorbidities or medication use potentially associated with development of peripheral neuropathy or neuromuscular disease
Age 4 months–20 years	Serious illnesses/comorbidities that would affect clinical or electrophysiological assessment in the view of the researchers
Functional status (non-sitter, sitter, walker)	Children who did not tolerate or were unwilling to undertake sequential studies
Receiving intrathecal nusinersen as part of clinical management at Sydney Children’s Hospital New South Wales, Australia	Children who were treated with a disease-modifying agent other than nusinersen
Written informed, voluntary consent given by parent/legal guardian or young person according to the principles set out in the Declaration of Helsinki: Consent forms were signed By parents for children <6 years. Parents and child for children 7–17 years old. Young person if >18 years of age. Non-English speakers were consented with the aid of an interpreter.