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.