Significance of visual hallucinations and cerebral hypometabolism in the risk of dementia in Parkinson's disease patients with mild cognitive impairment.

INTRODUCTION: Mild cognitive impairment (MCI) and visual hallucinations (VH) are common co-morbidities and risk factors for dementia in Parkinson's disease (PD). The relative value of each of them in the progression to dementia is unknown. We investigated cognitive impairment and cerebral hypometabolism in PD-MCI patients with VH (VH-positive) and without (VH-negative).
METHODS: Twenty-one PD-MCI patients (12 VH-negative, nine VH-positive) and 19 controls were studied using a comprehensive neuropsychological battery and [18F]-Fluorodeoxyglucose positron emission tomography (FDG-PET). The neuropsychological assessment was repeated after 30 months. Regional FDG uptake was analyzed using statistical parametric mapping.
RESULTS: VH-positive patients had lower FDG uptake bilaterally in the occipital, and parietal cortex, right temporal lobe and in the left cingulum compared with VH-negative patients. The two groups showed no significant differences in clinical characteristics and cognitive status at baseline. After 30 months of follow-up, three (25%) and four (50%) of the VH-negative and VH-positive patients, respectively, had progressed to dementia.
CONCLUSION: Even in the absence of significant cognitive differences, PD-MCI patients with VH exhibit more severe cerebral hypometabolism and had a higher rate of progression to dementia than VH-negative patients, supporting the importance of VH and cerebral hypometabolism in establishing the risk of dementia in PD-MCI.