CSF α-Synuclein Does Not Discriminate Dementia with Lewy Bodies from Alzheimer's Disease

In this study, we assessed whether cerebrospinal fluid (CSF) levels of the biomarker alpha-synuclein have a diagnostic value in differential diagnosis of dementia with Lewy bodies (DLB) and Alzheimer's disease (AD). We also analyzed associations between CSF biomarkers and cognitive performance in DLB and in AD. We included 35 DLB patients, 63 AD patients, 18 patients with Parkinson's disease (PD), and 34 patients with subjective complaints (SC). Neuropsychological performance was measured by means of the Mini-Mental Status Examination (MMSE), Visual Association Test (VAT), VAT object-naming, Trail Making Test, and category fluency. In CSF, levels of alpha-synuclein, amyloid-beta 1-42 (A beta(1-42)), total tau (tau), and tau phosphorylated at threonine 181 (ptau-181) were measured. CSF alpha-synuclein levels did not differentiate between diagnostic groups (p = 0.16). Higher ptau-181 and higher tau levels differentiated AD from DLB patients (p < 0.05). In DLB patients, lower A beta(1-42) and higher total tau levels were found than in SC and PD patients (p < 0.05). In DLB patients, linear regression analyses of CSF biomarkers showed that lower alpha-synuclein was related to lower MMSE-scores (beta(SE) = 6(2) and p < 0.05) and fluency (beta (SE) = 4(2), p < 0.05). Ultimately, CSF alpha-synuclein was not a useful diagnostic biomarker to differentiate DLB and/or PD (alpha-synucleinopathies) from AD or SC. In DLB patients maybe lower CSF alpha-synuclein levels are related to worse cognitive performance.