Brain metabolic correlates of dopaminergic degeneration in de novo idiopathic Parkinson's disease.

The aim of the present study was to evaluate the reciprocal relationships between motor impairment, dopaminergic dysfunction, and cerebral metabolism (rCMRglc) in de novo Parkinson's disease (PD) patients. Twenty-six de novo untreated PD patients were scanned with (123)I-FP-CIT SPECT and (18)F-FDG PET. The dopaminergic impairment was measured with putaminal (123)I-FP-CIT binding potential (BP), estimated with two different techniques: an iterative reconstruction algorithm (BP(OSEM)) and the least-squares (LS) method (BP(LS)). Statistical parametric mapping (SPM) multiple regression analyses were performed to determine the specific brain regions in which UPDRS III scores and putaminal BP values correlated with rCMRglc. The SPM results showed a negative correlation between UPDRS III and rCMRglc in premotor cortex, and a positive correlation between BP(OSEM) and rCMRglc in premotor and dorsolateral prefrontal cortex, not surviving at multiple comparison correction. Instead, there was a positive significant correlation between putaminal BP(LS) and rCMRglc in premotor, dorsolateral prefrontal, anterior prefrontal, and orbitofrontal cortex (p < 0.05, corrected for multiple comparison). Putaminal BP(LS) is an efficient parameter for exploring the correlations between PD severity and rCMRglc cortical changes. The correlation between dopaminergic degeneration and rCMRglc in several prefrontal regions likely represents the cortical functional correlate of the dysfunction in the motor basal ganglia-cortical circuit in PD. This finding suggests focusing on the metabolic course of these areas to follow PD progression and to analyze treatment effects.