According to meta-analysis results published in NeuroImage: Clinical, [18F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) is a reliable tool for detecting consistent functional brain abnormalities in Parkinson disease (PD) when compared with other imaging modalities.
For this study, researchers performed contrast analysis on different imaging modalities (ie, magnetic resonance imaging [MRI] and FDG-PET) and cross-validated results using a “unique approach integrating two meta-analytical algorithms.” A literature search and study selection yielded 3 subcohorts: PD-All, which contained all participants with PD, irrespective of clinical features; PD-Cog, which contained participants with cognitive impairment (either mild cognitive impairment or dementia); and PD-Motor, which contained participants with PD motor symptoms without specific behavioral or cognitive deficits. First, the Seed-based D Mapping approach was applied; second, the anatomic likelihood estimation method was applied; and last, the creation of an overlapping combination of both images was applied.
The researchers identified 74 studies for inclusion, with 2323 total participants with PD and 1767 healthy controls. The study demographic results showed mean age (65.6±5.5 years), 927 men, 728 women, and the average disease duration 7.2±4.4 years.
The meta-analysis results showed significant glucose hypometabolism in the PD-ALL “in the bilateral inferior parietal cortex and in the left caudate nucleus” when compared with healthy controls. Additionally, “the conjunction analysis of the PD-All < Controls contrast revealed small focal gray matter atrophy in the middle occipital gyrus.”
The study showed significant findings in the FDG-PET > MRI-voxel-based morphometry (VBM) contrast regarding the left caudate nucleus and right superior parietal cortex/precuneus. Both meta-analytical algorithms showed a reduction in glucose metabolism in the bilateral inferior parietal and right orbitofrontal cortexes in the PD-Cog subcohort. Conjunction analysis showed consistent glucose hypometabolism in the PD-Motor subcohort (compared with the control group). Diffusion tensor imaging studies revealed lower fractional anisotropy in the PD cohort as compared with the control group. Conjunction analysis revealed white matter atrophy in various regions in the PD cohort as compared with the control group.
This study identified the following limitations: lack of histopathologic confirmation of PD, the difference in technical and methodologic parameters of the included studies, the effect of pharmacologic treatment on PD, and the “exploratory nature of the subcohort analysis.”
Taken together, the authors suggest that “FDG-PET glucose metabolism is more consistently associated with PD as compared to brain atrophy as identified by MRI-VBM.”
Albrecht F, Ballarini T, Neumann J, Schroeter ML. FDG-PET hypometabolism is more sensitive than MRI atrophy in Parkinson’s disease: a whole-brain multimodal imaging meta-analysis [published online November 15, 2018]. Neuroimage Clin. doi: 10.1016/j.nicl.2018.11.004