Transcranial magnetic stimulation in benign childhood epilepsy with centro-temporal spikes

Motor cortical excitability was studied using transcranial magnetic stimulation (TMS) in 10 age-matched controls, and 13 children with benign childhood epilepsy with centro-temporal spikes (BECT), with a mean age of 11.2 +/- 2.0 years (five untreated, and eight treated with sodium valproate (VPA) and well controlled). Motor evoked potentials (MEPs) elicited by TMS through a circular coil were recorded from the first dorsal interosseous muscle (FDI) while relaxed. There was no significant difference in latency or duration of MEPs, or central motor conduction time among controls, untreated and treated patients. The threshold intensity for TMS in the untreated patients (63.0 +/- 14.8%, mean +/- SD) was similar to that in controls (63.0 +/- 12.5%), while the threshold intensity in the treated patients (79.4 +/- 11.8%) was significantly higher than that in the other groups. A significant increase in threshold intensity (15 +/- 4.1%) was also observed in the untreated patients retested after starting VPA treatment. No adverse effects occurred during TMS in any subjects. Thus, motor cortical hyperexcitability in BECT was not recognized in the present TMS study, while VPA was confirmed to have an effect on the threshold intensity for TMS.