CSF alpha‐synuclein aggregates by seed amplification and clinical presentation of AD

Accumulating evidence suggests that α-synuclein (αSyn) can modulate Alzheimer's disease (AD) pathology. The aim of this study was to evaluate the prevalence and clinical features associated with cerebrospinal fluid (CSF) αSyn detected by seed amplification assay (SAA) in AD.Eighty AD patients with CSF AT(N) biomarker positivity (mean age 70.3 ± 7.3 years) and 28 non-AD age-matched controls were included. All subjects underwent standardized clinical assessment; CSF αSyn aggregates were detected by SAA.CSF was αSyn-SAA positive (αSyn+) in 36/80 AD patients (45%) and in 2/28 controls (7.1%). AD αSyn+ and αSyn- patients were comparable for age, disease severity, comorbidity profile, and CSF core biomarkers. AD αSyn+ presented a higher prevalence of atypical phenotypes and symptoms.Our findings demonstrate that concomitant CSF αSyn pathology is present in a significant proportion of AD patients starting in the early stages and can affect clinical presentation. Longitudinal studies are warranted to evaluate the significance for the disease course.