C9orf72 and amyotrophic lateral sclerosis: Comparing all 267 normalized CSF samples (Fig. 5a and Extended Data Table 1), symptomatic C9orf72 mutation carriers had the highest average CSF:diluent signal ratios (mean 3.0, s.d. 8.7, range 0.69–71.20) followed by sporadic ALS (mean 1.8, s.d. 3.5, range 0.73–23.70) and presymptomatic C9orf72 mutation carriers (mean 1.7, s.d. 3.3, range 0.69–29.60).