Abstract
INTRODUCTION: Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) are essential for the early identification of non-amnestic phenotypes. Increased levels of total tau (t-tau) and phosphorylated tau (p-tau) have been reported in atypical AD cases, although the specific pattern remains a subject of debate. This study aimed to evaluate CSF biomarker profiles in relation to clinical phenotype. MATERIALS AND METHODS: A retrospective review was performed, analyzing demographic data, time to diagnosis, clinical phenotype, and core AD biomarkers (beta-amyloid peptide 1-42 (Aβ1-42), t-tau, p-tau) in CSF from patients evaluated at University Hospital in Navarra between 2019 and 2022. RESULTS: The study included 57 patients (54% female, mean age 67 years), of whom 41 met AD diagnostic criteria. Among these, 10 patients (25%) presented with atypical phenotypes (50% aphasic, 30% frontal, 20% mixed non-amnestic). Compared with the amnestic phenotype, the atypical group exhibited significantly higher t-tau (562.9 pg/mL vs 320.3 pg/mL, p = 0.021) and p-tau (81.5 pg/mL vs 37.7 pg/mL, p = 0.016) levels, independent of age, sex, and time to diagnosis. CONCLUSIONS: Atypical cases demonstrated increased tau levels, suggesting earlier and more extensive cortical damage than the amnestic phenotype. These findings underscore the significance of CSF biomarkers in phenotypic differentiation, disease course prediction, and individualized treatment strategies for AD.