Prognostic value of perivascular spaces, diffusion tensor imaging-derived indices, and choroid plexus in idiopathic normal pressure hydrocephalus

Background This study investigated the ability of the perivascular space (PVS), free water in the white matter (FW-WM), diffusion tensor imaging analysis along the PVS (DTI-ALPS), and choroid plexus (CP) to predict postoperative prognosis for idiopathic normal pressure hydrocephalus (iNPH), and the relationships between these MRI indices and clinical phenotypes. Methods This retrospective study included patients with iNPH who underwent magnetic resonance imaging (MRI) and clinical assessment using the modified Rankin Scale (mRS), iNPH grading scale (iNPHGS), timed up-and-go test (TUG), and Mini-Mental State Examination (MMSE). MRI indices included the PVS volume fraction (PVSVF), FW-WM fractional volume, DTI-ALPS, and CP volume fraction (CPVF). Predictors of improvement were analyzed using a logistic regression model and receiver operating characteristic analysis. Results The 32 enrolled patients (70 ± 7 years) included 17 men. The improvement rates in mRS, iNPHGS, MMSE, and TUG were 56% (18/32), 59% (19/32), 60% (15/25), and 57% (12/21), respectively. None of the examined MRI indices or clinical symptoms could predict which patients would show improvement after shunt surgery (all p  > 0.05). Lower DTI-ALPS scores were correlated with lower MMSE scores (r = 0.629; p corrected for false discovery rate [FDR] < 0.001). Higher FW-WM was correlated with higher TUG time (r = 0.563; p _FDR = 0.015) and steps (r = 0.521; p _FDR = 0.024). Conclusions Preoperative PVSVF, FW-WM, DTI-ALPS, and CPVF showed limited ability to predict the postoperative prognosis of iNPH. Higher FW-WM scores were correlated with gait impairment, whereas lower DTI-ALPS scores were correlated with cognitive impairment.