BACKGROUND: Parkinsonism is frequent in neurological conditions affecting gait and cognition, such as idiopathic normal pressure hydrocephalus (iNPH) and iNPH mimics, but its discriminating value between these two groups is still unidentified.

OBJECTIVE: This study aims to compare the prevalence of parkinsonism between iNPH and iNPH mimics and its discriminating value.

METHODS: Among 141 patients with suspicion of iNPH (75.7±7.1 years; 31.2% women), seventy-nine presented a possible or probable iNPH according to standardized diagnostic criteria and the remaining sixty-two were classified as iNPH mimics. Presence of parkinsonism and other seminal clinical symptoms of iNPH were systematically evaluated by a board-certified neurologist. Covariates include age, gender, comorbidities, and white matter disease burden using the age-related white matter changes scale. Logistic regressions were used to assess the association between parkinsonism and diagnostic groups.

RESULTS: Parkinsonism was present in 40.3% of iNPH mimics and 20.3% of iNPH (p-value: 0.015). The presence of parkinsonism, but not iNPH symptoms, was associated with the diagnosis of mimics in the adjusted model (adjusted odds ratio: 2.28; 95% CI: 1.06-4.93), even when age-related white matter changes were accounted for.

CONCLUSION: Compared to iNPH, the increased prevalence of parkinsonism in patients with iNPH mimics in the absence of significant white matter disease suggest an underlying neurodegenerative mechanism.