Low-frequency electric cortical stimulation has an inhibitory effect on epileptic focus in mesial temporal lobe epilepsy

Purpose: This study was conducted to investigate the effect of low-frequency electric cortical stimulation on epileptic focus in humans. Methods: We stimulated the epileptic focus in a patient with medically intractable mesial temporal lobe epilepsy (MTLE) by means of subdural electrodes and evaluated the change in the number of interictal epileptiform discharges. We used biphasic electric current of 0.3-ms duration presented at 0.9-Hz frequency for 250 s, comparing stimulus intensity of 7.5, 2, and 0.5 mA. Results: Interictal epileptiform discharges at the ictal focus occurred less frequently after the stimulation with the intensity of 0.5 mA. With the intensity of 7.5 mA and 2.0 mA, however, habitual auras were elicited by the stimulation, and afterdischarges were seen on the cortical EEG. Conclusions: Low-frequency, low-intensity electric cortical stimulation could produce inhibitory effects on epileptic activity. At the same time, however, a caution for possible induction of EEG seizures is needed, even when applying low-frequency electric stimulation.