Enhancement and bilateral synchronization of ripples in atypical benign epilepsy of childhood with centrotemporal spikes.

OBJECTIVE: To determine whether the characteristics of scalp-recorded high frequency oscillations, especially ripples, can predict the "atypical forms" of benign epilepsy of childhood with centrotemporal spikes (ABECTS), in BECTS.

METHODS: Seven patients with ABECTS and eighteen patients with BECTS underwent electroencephalography (EEG) in the secondary bilateral synchrony (SBS) and non-SBS periods for ABECTS patients. SBS period is that when more than 50% of the interictal epileptiform discharges (IEDs) are bilaterally synchronized. We determined the IED-ripple co-occurrence rate, performed time frequency analysis, and calculated the asymmetry index (AI).

RESULTS: The IEDs-ripple co-occurrence rate increased in the SBS compared to the non-SBS period. Time frequency analysis showed higher high-frequency activity rate and peak power in the SBS than in the non-SBS period. The AI was lower in ABECTS than BECTS, both in the non-SBS and SBS periods.

CONCLUSIONS: Ripples were enhanced in the SBS period of ABECTS, and bilaterally synchronized both in the non-SBS and SBS periods, whereas ripples in BECTS were localized unilaterally.

SIGNIFICANCE: Bilaterally synchronized ripples in the non-SBS period of ABECTS may distinguish ABECTS from BECTS in the non-SBS period of IEDs, and may be helpful for early detection of progressive neurophysiological regression leading to early intervention.