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

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.