Tommaso Schirinzi

Background and purpose Idiopathic normal pressure hydrocephalus (iNPH) pathogenesis is multifactorial. Systemic inflammation might have a role in gathering clinical–pathological trajectories. We aimed to shape the peripheral immune profile of iNPH and establish correlations with cerebrospinal fluid (CSF) markers, ventricular enlargement, and clinical outcomes. Methods We conducted a single‐center retrospective–longitudinal study, including 38 iNPH patients and 38 controls. Baseline iNPH Grading Scale and modified Rankin Scale (mRS) scores were collected with peripheral blood cell count, CSF amyloid‐β42 (Aβ42), total tau (t‐tau), phosphorylated‐181‐tau, and Evans index. Depending on 5‐year outcome, iNPH patients were grouped into “poor outcome” (PO; mRS ≥ 5) and “favorable outcome” (FO; mRS < 5). Biomarkers were compared and correlated with each other. Receiver operating characteristic analysis was performed. Results iNPH patients compared to controls had higher neutrophil‐to‐lymphocyte ratio (NLR; 2.43 ± 1.04 vs. 1.61 ± 0.47, p < 0.001), higher neutrophils (4.22 ± 0.86 1000/mL vs. 3.48 ± 1.34, p = 0.033), and lower lymphocytes (1.45 ± 0.55 1000/mL vs. 2.07 ± 0.86, p = 0.038), with the expected CSF biomarkers signature. In the patients' cohort, NLR was associated directly with t‐tau and inversely with Aβ42. NLR directly correlated with Evans index. PO patients compared to those with FO had higher NLR (3.25 ± 1.40 vs. 2.01 ± 0.77, p = 0.035) and higher t‐tau (274.76 ± 114.39 pg/mL vs. 150.28 ± 72.62, p = 0.017), with an area under the curve of 0.786 and 0.793, respectively. Conclusions iNPH patients present a proinflammatory state associated with neurodegeneration and predicting poor clinical outcome. Systemic inflammation represents a factor in the clinical–pathological progression of iNPH, and the NLR emerges as a potential prognostic index.