Cognitive correlates of interictal epileptiform discharges in adult patients with epilepsy in China

Abstract

Objective

Learning difficulties or cognitive impairment has been observed in many patients with epilepsy. Evidence from neurophysiologic and functional neuroimaging suggests that epileptic seizures and/or epileptiform activity can be the dominant factors inhibiting specific brain areas. However, most previous studies were focused on cognitive performance in children. In this study, we analyzed a new cohort of adult patients with frequent interictal epileptiform discharges (IEDs).

Methods

Data from 67 adult patients with epilepsy were reviewed. Electroencephalography (EEG)-video recording and cognitive testing were performed, and the IED index was estimated as a percentage assigned to one of four categories (<1%, 1–10%, 10–50%, and >50%) during either wakefulness or sleep. Correlations of cognitive test results and clinical characteristics of IED categories were analyzed. The effects of the frequency, duration, location, and sleep–wake cycles of IEDs on cognition (intelligence and memory capacity) were analyzed.

Results

Patients with an IED index >10% showed impaired performance on the Chinese Wechsler Adult Intelligence Scale (WAIS-RC) and the Chinese Wechsler Memory Scale (WMS). This effect was detected independently from other IED frequencies and other IED-related variables, such as duration, distribution, and location. The impact of waking or sleeping IEDs was of equal importance in contributing to impaired WAIS-RC and WMS performance.

Conclusion

An IED frequency of more than 10% in both waking and sleeping EEGs is associated with impaired cognitive performance in adult patients. However, whether patients with a high IED frequency but low seizure frequency will benefit from antiepileptic treatment should be examined in future studies.