The effect of age on motor deficits and cerebral glucose metabolism of Parkinson's disease

Background- No systematic study has been made to separate age-related clinical deterioration and dysfunctional brain areas from those associated with Parkinson's disease (PD). Methods- This study included 73 de novo patients with PD and 43 age-matched controls. All subjects underwent [ ¹⁸F]-fluorodeoxy glucose (FDG) positron emission tomography studies. The severity of parkinsonian motor deficit was measured using unified PD rating scale (UPDRS) motor scores. Multiple linear regression analysis was used to identify those parkinsonian motor deficits for which severity was correlated with the age of the patients and to locate brain areas in which normalized FDG uptake values were inversely correlated with the age of the subjects. Results- Patient age was positively correlated with total UPDRS motor scores and with subscores for bradykinesia and axial motor deficits, but not with subscores for tremor and rigidity. In the control group, an age-related decline in glucose uptake was found only in the cingulate cortex. However, in the patient group, an inverse correlation between age and glucose uptake was observed in the prefrontal, cingulate, orbitofrontal, perisylvian areas, caudate, and thalamus. Conclusions- In PD, widespread age-related decline in cerebral function may exaggerate the deterioration associated with bradykinesia and the axial motor deficits associated with nigral neuronal loss.