NEFL and amyotrophic lateral sclerosis: The levels of the axonal marker neurofilament light chain (NfL) in serum and cerebrospinal fluid (CSF) showed a treatment response earlier than clinical functional scores, what has recently been replicated in several real‐world cohorts of SOD1‐ALS patients treated with tofersen under the early access program (EAP) and since its approval.2, 3, 4, 5