High-frequency oscillations in idiopathic partial epilepsy of childhood.

PURPOSE

We explored high-frequency oscillations (HFOs) in scalp sleep electroencephalography (EEG) studies of patients with idiopathic partial epilepsy (IPE) of childhood in order to obtain a better understanding of the pathologic mechanisms underlying IPE.

METHODS

The subjects were 45 patients, including 32 with benign childhood epilepsy with centrotemporal spikes (BCECTS) and 13 with Panayiotopoulos syndrome (PS). A total of 136 EEG records were investigated through temporal expansion and filtering of traces and time-frequency spectral analysis.

KEY FINDINGS

HFOs with frequency of 93.8-152.3 Hz (mean 126.2 ± 13.6 Hz) in the band of ripples were detected in association with spikes in 97 records (71.3%). Time from last seizure to the EEG recording was significantly shorter in those with spike-related HFOs than in the EEG recordings with spikes without HFOs (p = 0.006). Although time from last seizure reflects age, age at the time of recording was not significantly different between EEG studies with and without HFOs. Peak-power values of the high-frequency spots in time-frequency spectra were significantly negatively correlated with time from last seizure (R(2) = 0.122, p < 0.001) but not with age at the time of recording. Peak frequencies of the high-frequency spectral spots were not significantly correlated with age at the time of recording or with time from last seizure.

SIGNIFICANCE

The close relationship between the generation of spike-related HFOs and the period of active seizure occurrence indicated that HFOs may tell us more about epileptogenicity in IPE than the spikes themselves. Because there is a spectrum of pediatric epileptic disorders extending from the benign end of BCECTS to the encephalopathic end of epilepsy with continuous spike-waves during slow-wave sleep (CSWS), and HFOs that have already been detected in association with CSWS were more prominent than HFOs in IPE, intense spike-related HFOs may indicate poor prognosis.