Hippocampal volume and white matter disease in the prediction of dementia in Parkinson's disease

Abstract

Background: Longitudinal neuroimaging studies could provide insights into pathophysiology of cognitive impairment in PD. We examined the role of hippocampal atrophy and cerebral white matter disease as risk factors for mild cognitive impairment and dementia in PD.

Methods: Prospective longitudinal study of patients with mild PD in a tertiary neurology center. All subjects underwent baseline MRI brain and had baseline and 6 monthly cognitive evaluations. Cognitive impairment was diagnosed based on the Movement Disorder Society Criteria. The predictive role of hippocampal volume and white matter hyperintensity at baseline on progression of cognitive impairment was studied.

Results: 97 subjects with mean age 65.3 years, mean education of 10.3 years and mean Hoehn & Yahr of 1.9 were studied. Over 2 years, 16 subjects developed mild cognitive impairment and 8 subjects with mild cognitive impairment progressed to dementia. After adjusting for age and vascular risk factors, hippocampal volume was a significant predictor for mild cognitive impairment (OR 7.05, CI 1.5-34.1; p = 0.015) and dementia (OR 7.03, CI 2.39-25.2; p = 0.001). With Cox regression, hippocampal volume was a significant predictor for "time to cognitive impairment" (HR 7.67; CI 3.47-16.95, p < 0.001). Difference between survival curves based on volume of white matter hyperintensity in predicting "time to mild cognitive impairment" was significant (p = 0.0295).

Conclusions: Hippocampal volume is a major factor predicting the development of mild cognitive impairment and dementia in PD. White matter hyperintensity also contributes to the longitudinal cognitive status in PD.

Keywords: Cerebrovascular disease; Cognition; Hippocampus; MRI; Parkinson's disease.