NEFL and amyotrophic lateral sclerosis: Lower CSF NfL levels have been noted in patients with ALS linked to superoxide dismutase (SOD1) mutations compared to cases with wild-type SOD1. 30 Independent studies in a group of consistently slowly progressive familial ALS patients homozygous for the SOD1 “D90A” mutation showed a curious relative sparing (in DTI terms) of CST involvement compared with sporadic ALS patients matched for disability and clinical UMN involvement.31 These two findings suggest that CSF NfL levels (and DTI measures) may be significantly influenced by genotype.