Scalp high-frequency oscillation spatial distribution is consistent over consecutive nights, while rates vary with antiseizure medication changes.

Objective: This study aimed to investigate two key aspects of scalp high-frequency oscillations (HFOs) in pediatric focal lesional epilepsy: (1) the stability of scalp HFO spatial distribution across consecutive nights, and (2) the variation in scalp HFO rates in response to changes in antiseizure medication (ASM).

Methods: We analyzed 81 whole-night scalp electroencephalography (EEG) recordings from 20 children with focal lesional epilepsy. We used a previously validated automated HFO detector to assess scalp HFO rates (80-250 Hz) during non-rapid eye movement (NREM) sleep. The spatial distribution of HFO rates across consecutive nights was evaluated using Hamming similarity, and changes in ASM were classified as increased, decreased, or stable.

Results: For each patient, we analyzed 3 ± 1 whole-night scalp EEG recordings, with a mean duration of 650 ± 215 min per recording. The distribution of HFO remained stable across consecutive nights, with a Hamming similarity of 88% ± 6%. Four patients had at least one ASM dosage decrease, nine patients had both ASM dosage decreases and increases, two patients had only ASM dosage increases, and five patients had no changes in ASM during the study period. A decrease in ASM dosage was associated with increased HFO rates (from .16 ± .32 to .22 ± .36 HFO/min; p = .03), whereas an increase in ASM dosage led to decreased HFO rates (from .32 ± .54 HFO/min to .22 ± .38 HFO/min; p = .005) when comparing the last night to the first.

Significance: The spatial distribution of scalp HFOs remained consistent across multiple nights, whereas fluctuations in HFO rates correlated with changes in ASM dosage. These findings suggest that scalp HFOs may not only help identify epileptogenic brain tissue but also monitor treatment response.