FDG-PET hypometabolism is more sensitive than MRI atrophy in Parkinson's disease: A whole-brain multimodal imaging meta-analysis

Abstract

Recently, revised diagnostic criteria for Parkinson's disease (PD) were introduced (Postuma et al., 2015). Yet, except for well-established dopaminergic imaging, validated imaging biomarkers for PD are still missing, though they could improve diagnostic accuracy.We conducted systematic meta-analyses to identify PD-specific markers in whole-brain structural magnetic resonance imaging (MRI), [18F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) and diffusion tensor imaging (DTI) studies. Overall, 74 studies were identified including 2323 patients and 1767 healthy controls. Studies were first grouped according to imaging modalities (MRI 50; PET 14; DTI 10) and then into subcohorts based on clinical phenotypes. To ensure reliable results, we combined established meta-analytical algorithms - anatomical likelihood estimation and seed-based D mapping - and cross-validated them in a conjunction analysis.Glucose hypometabolism was found using FDG-PET extensively in bilateral inferior parietal cortex and left caudate nucleus with both meta-analytic methods. This hypometabolism pattern was confirmed in subcohort analyses and related to cognitive deficits (inferior parietal cortex) and motor symptoms (caudate nucleus). Structural MRI showed only small focal gray matter atrophy in the middle occipital gyrus that was not confirmed in subcohort analyses. DTI revealed fractional anisotropy reductions in the cingulate bundle near the orbital and anterior cingulate gyri in PD.Our results suggest that FDG-PET reliably identifies consistent functional brain abnormalities in PD, whereas structural MRI and DTI show only focal alterations and rather inconsistent results. In conclusion, FDG-PET hypometabolism outperforms structural MRI in PD, although both imaging methods do not offer disease-specific imaging biomarkers for PD.

Parietal Perfusion Alterations in Parkinson's Disease Patients Without Dementia

“…A previous cross-sectional study investigating both metabolism and atrophy in cognitively impaired and cognitively preserved pwPD concluded that hypometabolism may precede GM volume loss and may be progressively replaced by atrophy during cognitive worsening (46). The greater ability of FDG-PET to reveal significant PD-related alterations compared to MRI-VBM is in line with this hypothesis (45). Parietal GM atrophy may be a feature that is mainly associated with late stage of PD, when cognitive impairment is already established.…”

“…The presence of parietal hypoperfusion in absence of parietal GM atrophy and its association with the TMT A score are the main findings that were observed. Although the majority of PD studies that have previously detected parietal hypoperfusion or hypometabolism included cognitively impaired cohort of subjects (11,15,(43)(44)(45), few works reported alterations in SPL (14,16) and IPL (14,46) even in absence of frank cognitive impairment. Cortical hypometabolism was detected in the posterior parietal cortex of non-demented PD patients with both phosphorus-31 magnetic resonance spectroscopy and FDG-PET (14).…”

Atrophy in midbrain & cerebral/cerebellar pedunculi is characteristic for progressive supranuclear palsy – A double-validation whole-brain meta-analysis

“…Finally, to investigate disease-specificity of the results, we ran subtraction analyses comparing the present results with the findings of our recently published meta-analysis on Parkinson's disease (For further information please refer to Albrecht et al, 2018). We used the results at p < 0.001 uncorrected from the present analysis and the white and gray matter MRI cohort of the Parkinson's disease meta-analysis (cohort with Parkinson's disease only).…”

“…To investigate disease-specificity we run subtraction analyses to compare PSP with related diseases, i.e. Parkinson's disease (Albrecht et al, 2018). We hypothesized atrophy in PSP of white matter in the midbrain and gray matter in the midbrain, thalamus, and insulae (Shao et al, 2014; Shi et al, 2013; Yu et al, 2015).…”

Neuroimaging Advances in Parkinson's Disease and Atypical Parkinsonian Syndromes

“…Preserved glucose metabolism in the basal ganglia may differentiate PD from MSA and PSP, where a corresponding glucose hypometabolism is typically seen in the latter (259). A meta-analysis found decreased glucose metabolism in the bilateral inferior parietal cortex and left caudate nucleus in PD, which was linked to cognitive deficits and motor symptoms, respectively (261). In MSA, glucose hypometabolism may be observed in the putamen and brainstem, with or without hypometabolism in the cerebellum compared to PD and controls (259,262).…”