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

Abstract

PurposeThe 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.

MethodsTwenty-six de novo untreated PD patients were scanned with 123I-FP-CIT SPECT and 18F-FDG PET. The dopaminergic impairment was measured with putaminal 123I-FP-CIT binding potential (BP), estimated with two different techniques: an iterative reconstruction algorithm (BPOSEM) and the least-squares (LS) method (BPLS). 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.

ResultsThe SPM results showed a negative correlation between UPDRS III and rCMRglc in premotor cortex, and a positive correlation
between BPOSEM and rCMRglc in premotor and dorsolateral prefrontal cortex, not surviving at multiple comparison correction. Instead, there
was a positive significant correlation between putaminal BPLS and rCMRglc in premotor, dorsolateral prefrontal, anterior prefrontal, and orbitofrontal cortex (p < 0.05, corrected for multiple comparison).

ConclusionsPutaminal BPLS 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.

KeywordsParkinson’s disease-FP-CIT-FDG-Basal ganglia