Objective: To explore the characteristics of the abnormal cerebral glucose metabolism and dopamine distribution in patients with Parkinson’s disease (PD) with bilateral onset.

Background: PD is usually characterized by unilateral onset and by loss of dopamine transporter (DAT) and a unique PD-related pattern (PDRP). However, we indeed found that some patients presented bilateral onset and were diagnosed as PD by follow-up.

Method: Twenty PD patients with bilateral onset (PD-Bi) and 45 with unilateral onset (PD-Uni), matched for age, sex, duration and UPDRS-III scores, were recruited. Twenty age-matched normal controls (NC) were also recruited. All subjects underwent ¹⁸F-FDG and ¹¹C-CFT PET at the same time. Scans from PD-Uni patients with predominantly right-sided symptoms were flipped and those from PD-Bi patients and NC were flipped randomly. PDRP expression was computed in each subject based on the PDRP we previously identified. Regional FDG metabolism was compared among groups using SPM.¹¹C-CFT uptakes of bilateral caudate, anterior and posterior putamen were calculated respectively by the striatal-to-occipital ratio (SOR) using ScAnVp toolbox and the asymmetric indices were calculated as the absolute value of (bilateral SOR difference/bilateral SOR average).

Results: UPDRS-III scores, of which the asymmetry indices were significantly lower in PD-Bi group (P<0.001), presented a significant difference between the bilateral limbs in PD-Uni group (P<0.001) but not in PD-Bi group.
The PDRP scores significantly increased in both PD groups relative to NC (P<0.001), but there was no difference between the two PD groups. Compared with PD-Uni, PD-Bi patients presented relative hypometabolism in the left middle frontal gyrus and inferior parietal lobule, and relative hypermetabolism in the right temporal, left parietal lobe and bilateral limbic lobe (P<0.001, uncorrected). 
DAT bindings significantly decreased in both PD groups compared with NC (P<0.001), and was lower in the posterior putamen in PD-Bi group than that in PD-Uni group (P=0.035).The asymmetric indices of both anterior and posterior putamen in PD-Bi group were significantly lower than those in PD-Uni group (P<0.05).

Conclusion: The differences of both cerebral glucose metabolism and dopamine dysfunction between PD-Bi and PD-Uni patients suggest PD-Bi might be another phenotype of the disease.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/abnormal-cerebral-glucose-metabolism-and-dopaminergic-dysfunction-in-patients-with-parkinsons-disease-with-bilateral-onset/