Objective: Parkinson’s Disease (PD), Progressive Supranuclear Palsy (PSP), Essential Tremor (ET), Dystonia (DYT), and Normal Pressure Hydrocephalus (NPH) may show overlapping clinical and radiological findings. Imaging markers are central in NPH diagnosis, yet NPH-like features have also been reported in PSP. This study compared Evans Index (EI), disproportionately enlarged subarachnoid-space hydrocephalus (DESH), and Callosal Angle (CA) among PD, ET, DYT, and PSP patients to assess their diagnostic contribution.

Background: We hypothesized that EI, DESH, and CA — established markers in NPH imaging — may also help differentiate PD, ET, DYT, and PSP.

Method: In this retrospective cohort study, 121 patients were included: 43 PD, 43 ET, 19 DYT, and 16 PSP. Brain MRI scans were systematically reviewed. EI, DESH, and CA were measured independently and blindly by three movement disorder specialists.

Results: The dystonia group was the youngest (median age 41) with the longest disease duration (median 12 years, p <0.001). The PSP group was the oldest (median 70). PSP patients showed significantly higher EI values (median 0.27) compared to PD, ET, and DYT (p <0.001). CA values were preserved in all groups (median 118°–129°), remaining above the 90° NPH threshold. Although slightly narrower angles were observed in PSP and PD, no significant intergroup difference was found (p =0.13). DESH pattern was absent in all patients (0%). Importantly, high EI in PSP was not accompanied by narrow CA or DESH.

Conclusion: EI alone is insufficient and non-specific for diagnosing NPH. In PSP, elevated EI likely reflects central atrophy (hydrocephalus ex vacuo) rather than true NPH. Unlike NPH, PSP patients did not demonstrate narrow CA (<90°) or DESH. Thus, ventricular enlargement or high EI in movement disorders — particularly PSP — may lead to misdiagnosis if interpreted in isolation. The absence of DESH and preservation of a wide CA are reliable markers arguing against NPH and favoring neurodegeneration. Larger studies are needed to clarify the relationship between NPH-like MRI findings and Parkinsonian syndromes and to define the diagnostic value of NPH-related imaging markers.

References: 1. Fu MH, Huang CC, Wu KLH, Chen YF, Kung YC, Lee CC, Liu JS, Lan MY, Chang YY.
Higher prevalence of idiopathic normal pressure hydrocephalus-like MRI features in progressive supranuclear palsy: An imaging reminder of atypical parkinsonism. Brain Behav. 2023;13:e2884.
2. Cogswell P, Switzer A.Radiographic Evaluation of Normal Pressure Hydrocephalus. Continuum (Minneap Minn). 2025;31:813–839.
3. Campo-Caballero D, Ash E, Fasano A, et al. Clinical and Radiological Evolution of Idiopathic Normal Pressure Hydrocephalus: A Critical Review. Mov Disord Clin Pract. Published online November 3, 2025. doi:10.1002/mdc3.70419

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MDS Abstracts - https://www.mdsabstracts.org/abstract/normal-pressure-hydrocephalus-imaging-markers-in-movement-disorders-comparison-of-parkinsons-disease-essential-tremor-dystonia-and-progressive-supranuclear-palsy/