Patients with benign rolandic epilepsy have a longer duration of somatosensory evoked high-frequency oscillations

Background: High-frequency oscillations (HFO) ranging between 300-900 Hz have been shown to be Superimposed on an early component of somatosensory evoked potentials (SEP) to median nerve stimulation in humans. Although the HFO are speculated to be a localized activity of the GABAergic inhibitory interneurons, the significance in the epileptogenicity remains unclear. The authors of this study analyzed HFO using magnetoencephalography in patients with benign rolandic epilepsy (BRE) to clarify the neurophysiological basis of rolandic discharges (RD). Methods: Nine patients with BRE and six patients with other epileptic syndrome (non-BRE) participated in the study. Somatosensory evoked fields (SEF) including HFO to median nerve stimulation were measured in a magnetically shielded room with a 37-channel neuromagnetometer. Results: Two kinds of HFO, 300 Hz- and 600 Hz-HFO, were identified and the duration of the HFO in patients with BRE was significantly longer than that in patients with non-BRE. Conclusions: The results suggest that the longer part of HFO (P30m-related) is closely related to the pathogenesis of RD and that the longer HFO in patients with BRE might be mediated by altered GABAergic inhibition modulated by the cholinergic system.