Cerebrospinal Fluid Amyloid-β Oligomer Levels in Patients with Idiopathic Normal Pressure Hydrocephalus

Background: The amyloid-β oligomers, consisting of 10–20 monomers (AβO10–20), have strong neurotoxicity and are associated with cognitive impairment in Alzheimer’s disease (AD). However, their role in patients with idiopathic normal pressure hydrocephalus (iNPH) is poorly understood. Objective: We hypothesized that cerebrospinal fluid (CSF) AβO10–20 accumulates in patients with iNPH, and its clearance after CSF shunting contributes to neurological improvement. We measured CSF AβO10–20 levels before and after CSF shunting in iNPH patients evaluating their diagnostic and prognostic role. Methods: We evaluated two iNPH cohorts: “evaluation” (cohort-1) with 32 patients and “validation” (cohort-2) with 13 patients. Comparison cohorts included: 27 neurologically healthy controls (HCs), and 16 AD, 15 Parkinson’s disease (PD), and 14 progressive supranuclear palsy (PSP) patients. We assessed for all cohorts CSF AβO10–20 levels and their comprehensive clinical data. iNPH cohort-1 pre-shunting data were compared with those of comparison cohorts, using cohort-2 for validation. Next, we compared cohort-1’s clinical and CSF data: 1) before and after CSF shunting, and 2) increased versus decreased AβO10–20 levels at baseline, 1 and 3 years after shunting. Results: Cohort-1 had higher CSF AβO10–20 levels than the HCs, PD, and PSP cohorts. This result was validated with data from cohort-2. CSF AβO10–20 levels differentiated cohort-1 from the PD and PSP groups, with an area under receiver operating characteristic curve of 0.94. AβO10–20 levels in cohort-1 decreased after CSF shunting. Patients with AβO10–20 decrease showed better cognitive outcome than those without. Conclusion: AβO10–20 accumulates in patients with iNPH and is eliminated by CSF shunting. AβO10–20 can be an applicable diagnostic and prognostic biomarker.