HDGFL2 and normal pressure hydrocephalus: A TDP-43-dependent cryptic epitopes, hepatoma-derived growth factor-like protein 2 (HDGFL2), has been recently detected to be increased via sandwich ELISA in CSF samples of different cohorts of C9ORF72 ALS patients, C9ORF72 presymptomatic carriers and sporadic ALS patients, compared to healthy individuals and neurologic controls with diagnoses of migraine and normal pressure hydrocephalus (NPH) [80], proposing a novel, specific CSF biomarker for ALS far earlier than neurofilament chains.