Unidirectional flow establishes a rostro‐caudal gradient (Aasebø et al., 2014) that results in lower concentrations of brain proteins such as S‐100β, total Tau, and phosphorylated Tau in the lumbar region than in the cisternal region, depending on the type of neurological disorder, if present (Brandner et al., 2014; Reiber, 2003). Here, MAPT is linked to nervous system disorder.