Correlation between dopaminergic and metabolic asymmetry in Lewy body disease – A dual-imaging study

Introduction

The $a$-Synuclein Origin and Connectome (SOC) model of Lewy body diseases postulates that $a$-syuclein will be asymmetrically distributed in some patients with Lewy body diseases, potentially leading to asymmetric neuronal dysfunction and symptoms.

Methods

We included two patient groups: 19 non-demented Parkinson's disease (nPD) patients with [¹⁸F]FDG PET and motor symptoms assessed by UPDRS-III, and 65 Lewy body dementia (LBD) patients with [¹⁸F]FDG PET and dopamine radioisotope imaging. Asymmetry indices were calculated for [¹⁸F]FDG PET by including the cortex for each hemisphere, for dopamine radioisotope imaging by including the putamen and caudate separately, and for motor symptoms by using the difference between right-left UPDRS-III score. Correlations between these asymmetry indices were explored to test the predictions of the SOC model. To identify cases with a more typical LBD imaging profile, we calculated a Cingulate Island Sign (CIS) index on the [¹⁸F]FDG PET image.

Results

We found a significant correlation between cortical interhemispheric [¹⁸F]FDG asymmetry and motor-symptom asymmetry in nPD patients (r = 0.62, P = 0.004). In patients with LBD, we found a significant correlation between cortical interhemispheric [¹⁸F]FDG asymmetry and dopamine transporter asymmetry in the caudate (r = 0.37, P = 0.0019), but not in the putamen (r = 0.15, P = 0.22). We observed that the correlation in the caudate was stronger in LBD subjects with the highest CIS index, i.e., with more typical LBD imaging profiles.

Conclusion

Our study partly supports the SOC model, but further investigations are needed – ideally of de novo, non-demented PD patients.