Normal Pressure Hydrocephalus: Clinical Symptoms, Cerebrospinal Fluid Flow Metrics and White Matter Changes

The aim of this study was to investigate correlations between clinical symptoms, cerebrospinal fluid flow metrics, hydrocephalus index, small-vessel disease, and white matter (WM) changes in normal pressure hydrocephalus (NPH).

Aquaductal stroke volumes (ASVs), Z Evans index, Fazekas grading (FG), and diffusion tensor imaging measurements from WM bundles of 37 patients with NPH were retrospectively evaluated. Mann-Whitney U test between clinical symptoms and other variables and Spearman ρ correlations for relationships between variables and Kruskal-Wallis to correlate FG with nonclinical variables were used.

Patients with NPH had increased ASV (median 53 μL). No correlation was found between Z Evans index and ASV. Three groups of patients with dementia or ataxia or incontinence had increased ASV values than their counterparts without symptoms (55 vs 48.5 μL, 75 vs 47 μL, 64 vs 49.5 μL, respectively). Patients having 2 common symptoms of dementia and ataxia and patients having all 3 symptoms of dementia, ataxia, and incontinence were compared with ASV values of 63.5 versus 78 μL, respectively. Patients with FG 1 had median ASV values of 45 μL; FG 2, 82.5 μL; and FG 3, 59 μL. Patients with dementia had significantly higher apparent diffusion coefficient (ADC) values of corona radiata (CR) on both sides. There were no significant WM changes in patients with ataxia and incontinence. The Z Evans index was positively correlated with ADC values of CR on both sides and genu of corpus callosum. Fazekas grading was found positively correlated with ADC and negatively correlated with FA values of CR.

Patients with NPH, regardless of stages of the diseases, have increased ASV values and could benefit from shunting. Decreasing ASV values of patients with FG 3 comparing with those with FG 2 support the hypothesis of decreasing compliance of brain with aging and increasing severity of small-vessel disease.