The relationship between electroencephalography characteristics and intellectual development indicators in self-limited focal childhood epilepsy (pilot study)

Background. Self-limited (age-dependent) focal epilepsies (SeLFE) are characterized by a relatively favorable course, a good response to antiepileptic medications, and spontaneous self-resolution during puberty. They are characterized by detecting a specific electroencephalographic (EEG) pattern – benign epileptiform discharges of childhood, with their prevalence tending to increase during slow-wave sleep, extending to extremely high degree in some cases. Literature data report about certain transient and persistent impairments of higher mental functions in patients with SeLFE, primarily in the areas of speech, memory, attention, and educational performance. In this regard, a significant role is attributed to EEG-recorded epileptiform activity, especially during video-EEG monitoring. However, studies with objective evidence base assessing an impact of epileptiform activity on intellectual development in patients with SeLFE are currently sparse, whereas the results of available reports are extremely contradictory in most cases being limited to examining self-limited epilepsy with centrotemporal spikes.

Objective: To determine an impact of various EEG parameters on intellectual development in patients with SeLFE syndromes.

Material and methods. The study group included 41 children with SeLFE diagnosed based on medical history, neurological, and instrumental examinations in accordance with the 2022 International League Against Epilepsy criteria. All children underwent video-EEG monitoring in sleep state with spike-wave index (SWI) calculation, assessed location and quantity of epileptiform foci, as well as with comprehensively analyzed intellectual functions using the Wechsler Intelligence Scale for Children 2 and the Vineland Adaptive Behavior Scale 2. The control group consisted of 30 children with no history of neuropsychiatric disorders or EEG changes.

Results. One EEG epileptiform focus was recorded in 20 (48.8%) patients, while 21 (51.2%) subjects had two or more epileptiform foci. Left hemisphere discharges were detected in 11 (26.8%) children, right hemisphere discharges – in 8 (19.6%), and bilateral discharges – in 22 (53.6%). Analysis of SWI values on sleep EEG revealed that in 13 (31.7%) patients they exceeded 50% level, with 7 (17.1%) cases showing high discharge index (≥85% of sleep recording). Correlation analysis of SWI level in different patient groups showed a wide range of negative correlations with separate indicators of intellectual development.

Conclusion. The SWI level is a key factor determining the intellectual impairment. Location of focal discharges determines the specific impact of SWI on cognitive functions, whereas the number of foci influences on dynamics of intellectual impairment. In some cases (especially in patients with two foci and bilateral localization), the dynamics vs. absolute rate of SWI levels is of greater importance.

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