Cognitive and Biomarker Signatures of Late-Onset Temporal Lobe Epilepsy

BACKGROUND AND OBJECTIVES: Late-onset unexplained epilepsy (LOUE) represents a substantial proportion of epilepsies with onset after 50 years and often manifests as temporal lobe epilepsy (LO-TLE). Although a link with Alzheimer disease (AD) has been suggested, only a subset of LO-TLE shows AD-related biomarkers, indicating biological heterogeneity. This study aims to characterize the cognitive and CSF phenotype of LO-TLE and compare it with healthy controls (HCs) and patients with mild cognitive impairment due to AD (MCI-AD). METHODS: This Italian cross-sectional cohort study included LO-TLE patients with normal CSF β-amyloid (Aβ) biomarkers, MCI-AD, and age-matched and sex-matched HC. Participants underwent structural MRI, neuropsychological assessment, and CSF biomarkers assay, including neurofilament light chain (NfL) and the phosphorylated-to-total tau ratio (p/t-tau). Cortical thickness and subcortical volumes were quantified from structural MRI. Cognitive performance was summarized using principal component analyses. Group differences in imaging, cognition, and CSF biomarkers were assessed, and associations between CSF markers and cognition were examined within groups. RESULTS: = 0.032), whereas no associations emerged in MCI-AD. DISCUSSION: LO-TLE with normal CSF AD biomarkers is characterized by distinct cognitive and biological features compared with MCI-AD, suggesting a disease process independent of AD. The low p/t-tau ratio may reflect alternative pathophysiologic mechanisms and warrants further investigation in larger longitudinal studies to clarify the underlying pathology and clinical trajectories.