C9+ ALS patients had a hyperexcitable profile with larger refractoriness at 2 ms and relative refractory periods than C9− ALS patients (t = 4.58, p < 0.001; t = 3.43, p = 0.002, respectively), which is in line with slower recovery of the Na+‐channels from inactivation. This evidence concerns the gene C9 and amyotrophic lateral sclerosis.