Cortical hypometabolism assessed by a metabolic ratio in Parkinson's disease primarily reflects cognitive deterioration-[18F]FDG-PET.

In Parkinson's disease patients with cognitive deterioration, regional cortical hypometabolism has been observed with [(18)F]fluorodeoxyglucose-positron emission tomography (FDG-PET). Our aim was to develop a robust method to subsume the overall degree of metabolic deterioration in Parkinson's disease by means of a single index and to investigate which of the clinical features correlates best with hypometabolism. Twenty-two Parkinson's patients (10 demented) and seven controls underwent FDG-PET. A metabolic index (mean relative uptake in typically affected regions) was calculated for each patient and compared with scores for cognition [Minimental State Examination (MMSE)], motor performance [Unified Parkinson's Disease Rating Scale (UPDRS III)" and behavior (Neuropsychiatric Inventory). In stepwise linear regression analysis, MMSE (P < 0.001) score showed the only significant effect. Estimated sensitivity and specificity for DSM-IV diagnosis of dementia were high for the metabolic index (MI), with 91 and 100%. Taken together, the presented data indicate that cerebral hypometabolism in Parkinson's disease is primarily associated with cognitive impairment.