Evaluation of Interstitial Fluid Volume and Diffusivity in Patients With Idiopathic Normal Pressure Hydrocephalus Using Spectral Diffusion Analysis.

BACKGROUND

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).

PURPOSE: To compare F int and D int between patients with iNPH and healthy controls (HCs).

STUDY TYPE: Retrospective.

POPULATION: 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).

FIELD STRENGTH/SEQUENCE: 3.0 T/Single-shot spin-echo echo-planar imaging.

ASSESSMENT: 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 (iNPHPVH group) or non-PVH regions (iNPH group). F int and D int were compared among groups, and correlations with age were analyzed.

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

RESULTS

In the CSO, iNPHPVH 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 iNPHPVH 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).

DATA

CONCLUSION

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.

EVIDENCE LEVEL: 3.

TECHNICAL EFFICACY: Stage 1.