Features of cognitive dysfunction in late-onset temporal lobe epilepsy

Abstract

Objective: A global increase in the aging population has resulted in more patients with late-onset epilepsy. Late-onset temporal lobe epilepsy (LOTLE) is one of the most common types of late-onset epilepsy and is frequently accompanied by memory impairments. Here, we investigated the relationships between memory function and clinical characteristics, including findings from long-term video-electroencephalograph (LVEEG) monitoring, in LOTLE.

Methods: We evaluated patients who had been diagnosed with LOTLE and Underwent LVEEG and neuropsychological tests (e.g., the Wechsler Memory Scale-Revised [WMS-R]) before the introduction of anti-seizure medications at our epilepsy center. We then performed multiple regression analyses using patients' clinical characteristics, including LVEEG data, as the independent variables, and cognitive scores as the dependent variables.

Results: We included 17 patients with LOTLE. The mean age at onset was 65.18 ± 8.35 (47-78) years old. Among the WMS-R domains, verbal memory (β = -.79, p < .001), visual memory (β = -.645, p = .005), general memory (β = -.838, p < .001), and attention (β = -1.334, p < .001) showed negative relationships with the number of seizures of left temporal origin captured by LVEEG. Furthermore, patients who experienced transient amnestic episodes had relatively better delayed recall scores at 30 min (β = -.606, p = .005).

Significance: Our findings suggest that frequent seizures originating from the left temporal lobe impair various cognitive functions. They also indicate that the patterns of cognitive dysfunction in LOTLE may be divided into two types: one showing preserved delayed recall with transient epileptic amnesia, and one showing impaired delayed recall.

Keywords: Wechsler Memory Scale; cognitive dysfunction; late‐onset temporal lobe epilepsy; long‐term video‐electroencephalograph; transient epileptic amnesia.

FIGURE 1

Temporal lobe epilepsy–specific bipolar montage used for the evaluation of ictal discharge. The top half is a bipolar montage starting at the O2 electrode, passing through the left temporal–frontal pole–right temporal regions, and ending at O1. The lower half of the montage emphasizes the anterior temporal electrodes (F7, T3; F8, T4). This ictal discharge is from a 68‐year‐old woman who had left amygdala enlargement on MRI; it shows a slow wave burst that begins near the anterior left temporal region and gradually increases in amplitude. FIQ, Full Intelligence Quotient; WAIS, Wechsler Adult Intelligence Scale; WMS‐R, Wechsler Memory Scale‐Revised.

FIGURE 2

Significant relationships between clinical features and cognitive performance. The number of seizures of left temporal origin observed by long‐term video‐electroencephalograph was negatively correlated with verbal memory (A), visual memory (B), general memory (C), and attention (D) performance. Patients who experienced TEA episodes showed relatively better delayed recall scores (E). FIQ, Full Intelligence Quotient; TEA, transient epileptic amnesia.

FIGURE 3

Relationships between seizure number (total and of left temporal origin) and delayed recall performance and TEA. It can be observed that the TEA group had fewer seizures. However, there were no significant associations between seizure number and delayed recall performance, and there were no confounding factors for TEA (such as the number of seizures) in our statistical analyses. FIQ, Full Intelligence Quotient; TEA, transient epileptic amnesia.