Objective:

To investigate the role of age in the presence of high frequency oscillations (HFOs) on scalp electroencephalograms (EEGs) in a large pediatric cohort suspected or diagnosed with epilepsy. 

Background:

HFOs have been widely reported in invasive recordings as epileptogenic biomarkers. Whether they can be reliably detected on non-invasive scalp EEGs has been the focus of recent interest. Whereas spontaneously-occurring ripples (100-250 Hz) can be associated with either physiological or pathological activity, spontaneously-occurring fast ripples (FRs; 250-500 Hz) are pathological and can therefore serve as an important non-invasive epileptogenic biomarker. Whether the faster FR can be visually and reliably detected, and whether FR can be equally detected across age groups is not clear.

Design/Methods:

For patients admitted to our institution for whom a video-EEG was obtained for clinical diagnosis and management, all video-EEGs recorded at 2048 Hz sampling rate with a 500 Hz high frequency filter were visually reviewed for FR during 10-minute artifact-free sleep epochs. All artifacts were excluded, and the presence or absence of scalp FRs was tallied. Data were assessed with R studio: 1) continuously by years of age, and 2) by age bins: Infants (0-2 years), Children (2-13 years) and Teens (13+ years).

Results:

After a total of 1597 video-EEGs were assessed for FR, with the continuous age data analysis, FR presence was noted across the age spectrum and varied significantly across age (p=0.002 ), peaking during mid-childhood years, and less frequently detected in infants and teens. When categorized into age bins, FR prevalence was also highest in children (37.9%) compared to infants (27.1%) and adolescents (26.4%; p<0.001).

Conclusions:

This study shows 1) that scalp FR can be visually and reliably detected in sleep in a large pediatric cohort; and 2) that scalp FR appears age-based within the pediatric population, most prevalent in children, followed by infants, and least prevalent in teens.