Cerebrospinal Tau, Phospho-Tau, and Beta-Amyloid and Neuropsychological Functions in Alzheiemer' Disease and Parkinson's Disease

The aim of this study was to assess cerebrospinal fluid (CSF) levels of total tau, phospho-tau, and beta-amyloid, proposed as biomarkers for Alzheiemer' s disease (AD), and their relationship with cognitive function in Parkinson's disease (PD). Seventy-eight patients with AD and 40 PD patients (20 nondemented (PDND); 20 demeneted (PDD] and 50 controls underwent CSF tau, phospho-tau, and beta-amyloid analysis using specific ELISA techniques. All AD and PD patients and controls underwent neuropsychological testing of fronto-subcortical (attention, fluency) and neocortical (memory, naming, visuoperceptive) functions. CSF markers levels were compared between groups, and compared and correlated with neuropsychological measures in PDND and PDD separately and as a continuum (PD) with AD and controls. CSF tau and phospho-tau were higher in AD and PDD than in PDND and controls (P < 0.05). CSF beta-amyloid ranged from high (controls) to intermediate (PDND), and low (PDD) levels (P < 0.001), with the lowest values in AD subjects. In all PD and PDD patients, high CSF tau and phospho-tau were associated with impaired memory and naming. In PDND, CSF beta-amyloid was related with phonemic fluency. These findings suggest that dementia in PD and lower cognitive functioning are associated with higher CSF tau and phospo-tau levels. The lower CSF beta-amyloid in PDND patients with impaired phonemic fluency could constitute an early marker of cognitive dysfunction.