Cerebrospinal Fluid Biomarkers in Parkinson's Disease with Dementia and Dementia with Lewy Bodies

Background: Clinical criteria for differentiating Parkinson's disease (PD) with dementia (PDD) from dementia with Lewy bodies (DLB) are unsatisfactory. Their existence as distinct clinicopathologic entities is still debated, although the burden of Alzheimer's disease (AD) pathology seems higher in DLB. Thus, analysis of cerebrospinal fluid (CSF) biomarkers (β-amyloid_1-42 [Aβ42], total tau, and hyperphosphorylated tau [p-tau]) in living subjects might provide significant pathophysiological information on these diseases. Methods: Cerebrospinal fluid biomarkers were measured in DLB (n = 19), PDD (n = 18), and AD (n = 23) subjects matched for age, sex, and dementia severity, as well as in PD (n = 20) and normal control subjects (n = 20). Results: DLB showed the lowest mean CSF Aβ42 levels, with a negative association to dementia duration (ρ = -.42, p = .07). In DLB patients, mean CSF total tau levels were significantly lower than in AD patients (508 ± 387 vs. 960 ± 619, respectively) but twofold to threefold higher than in PDD (286 ± 184), PD (160 ± 64), or normal control subjects (177 ± 76), with a positive association to dementia severity (Mini-Mental State Examination: ρ = -.54, p = .02; Milan Overall Dementia Assessment: ρ = -.66, p = .002). PDD patients had mean CSF Aβ42 and total tau levels similar to those seen in PD patients. Hyperphosphorylated tau was significantly increased in the AD group only. Conclusions: Cerebrospinal fluid Aβ42 and total tau have a different behavior in DLB and PDD, being related to duration and severity of dementia in DLB alone. Hyperphosphorylated tau is not significantly altered in these conditions.