Evaluation of Interstitial Fluid Volume and Diffusivity in Patients With Idiopathic Normal Pressure Hydrocephalus...

Changes in interstitial fluid (ISF) dynamics are potential contributors to idiopathic normal pressure hydrocephalus (iNPH). Spectral diffusion analysis provides surrogate markers for ISF volume (F _int) and diffusivity (D _int).

To compare F _int and D _int between patients with iNPH and healthy controls (HCs).

Retrospective.

34 patients with iNPH (24 males, 10 females; 76.9 ± 7.6 years) and 132 HCs (46 males, 86 females; 47.5 ± 16.9 years; three age groups: < 40 years, 40-59 years, and ≥ 60 years).

3.0 T/Single-shot spin-echo echo-planar imaging.

F _int and D _int were computed using non-negative least squares and measured in eight regions, including the centrum semiovale (CSO), frontal white matter (FWM), and lenticular nucleus (LN). The regions of interest of iNPH were categorized as either periventricular hyperintensity (PVH) regions (iNPH_PVH group) or non-PVH regions (iNPH group). F _int and D _int were compared among groups, and correlations with age were analyzed.

Kruskal-Wallis test with Dunn's multiple comparison post hoc test. Spearman correlation coefficient. p < 0.05 was considered statistically significant.

In the CSO, iNPH_PVH group F _int values (40.3% ± 18.4%) exceeded those of other groups, while D _int values (1.53 ± 0.63 [× 10^-3 mm²/s]) were significantly higher than those in younger HCs and the iNPH group. In the FWM, both F _int (53.0% ± 18.9%) and D _int (1.64 ± 0.50 [× 10^-3 mm²/s]) were significantly higher in the iNPH_PVH group than in the other groups. In the LN, F _int correlated positively with age, regardless of the iNPH group's inclusion (without iNPH, ρ = 0.2114; with iNPH, ρ = 0.3044).

Spectral diffusion analysis in iNPH demonstrated that ISF volume and diffusivity increased in PVH regions of the CSO and FWM, whereas ISF dynamics outside PVH regions may not differ significantly from those in HCs.

3.

Stage 1.