Synuclein Motor Dysfunction Composite Scale for the Discrimination of Dementia With Lewy Bodies From Alzheimer's Disease

Background: An abnormal increase of alpha-synuclein in the brain is the hallmark of dementia with Lewy bodies (DLB). However, the diagnostic power of plasma alpha-synuclein in DLB is not yet confirmed. Parkinsonism is highly associated with and is one of the core clinical features of DLB. We studied plasma alpha-synuclein and developed a novel tool that combined plasma alpha-synuclein level and Motor Dysfunction Questionnaire (MDQ), namely Synuclein Motor Dysfunction Composite Scale (SMDCS), for the clinical discrimination of DLB from Alzheimer's disease (AD). Methods: This cross-sectional study analyzed participants' demographical data, plasma alpha-synuclein level, MDQ, structured clinical history questionnaire, neuropsychological and motor function tests, and neuroimaging studies. The power of plasma alpha-synuclein level, MDQ, and SMDCS for discriminating DLB from non-demented controls (NC) or AD were compared. Results: Overall, 121 participants diagnosed as 58 DLB, 31 AD, and 31 NC were enrolled. Patients with DLB had significantly higher mean plasma alpha-synuclein level (0.24 +/- 0.32 pg/ml) compared to the NC group (0.08 & PLUSMN; 0.05 pg/ml) and the AD group (0.08 +/- 0.05 pg/ml). The DLB group demonstrated higher MDQ (2.95 +/- 1.60) compared to the NC (0.42 +/- 0.98) or AD (0.44 +/- 0.99) groups. The sensitivity/specificity of plasma alpha-synuclein level, MDQ, and SMDCS for differentiating DLB from non-DLB were 0.80/0.64, 0.83/0.89, and 0.88/0.93, respectively. Conclusion: Both plasma alpha-synuclein and MDQ were significantly higher in patients with DLB compared to the NC or AD groups. The novel SMDCS, significantly improved accuracy for the clinical differentiation of DLB from AD or NC.