In-session seizures during transcranial direct current stimulation in patients with epilepsy

Abstract

Cathodal transcranial direct current stimulation (c-tDCS) has capacity to suppress ongoing seizures in animal epilepsy models [1e3]. However, whether ictal c-tDCS, can interrupt seizures in humans has not been tested. Further, while patients with epilepsy undergoing c-tDCS may have seizures during the stimulation session, whether these seizures are more or less severe relative to their habitual seizures has not been documented. In a recent trial aimed to test the antiepileptic c-tDCS capacity, we enrolled three children with frequent (4e120 multiple per day) medically refractory seizures, and recorded seizures both before and during c-tDCS. Each participant underwent c-tDCS (2mA, 30 min per day for 10 days) with simultaneous EEG. One week before stimulation, all patients also underwent 60 minutes routine scalp video-EEG recording where the duration of their habitual seizure was measured. Each patient was prescribed a personalized set of stimulation parameters (a “stimulation montage”). Montages with up to 8 electrodes were used, the cathode electrode was located over the most active epileptiform discharge region. The anode electrode was sited over a contralateral region to obtain a focal effect. Themultichannel tDCS stimulator used was the StarstimTM 8 device (Neuroelectrics Corporation, Cambridge, MA). The electrical dose was give using multiple PISTIM electrodes (circular electrodes with a radius of 1 cm, with a contact surface of 3.14 cm2). During each daily session, a maximum total current (across all electrodes) of 2 mA 30 min was applied with a maximum at any one electrode of 600 mA/cm2. Cathodal tDCS treatment was utilized during 10 days with simultaneous EEG recording using the same protocol EEG monitoring included raw data and spectrograms. Each patient’s stimula-