Malm et al. considering that a similar biochemical disturbance to that of patients with different forms of dementia, namely disturbance in the cholinergic, serotonergic and noradrenergic system would occur in patients with NPH, measured the levels of 3-methoxy-4-hydroxy-phenylglycol (MHPG), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA), acetylcholinesterase (AChE) and butyryl cholinesterase (BuChE) [38]. Here, ACHE is linked to normal pressure hydrocephalus.