Study treatment
CORTEX
During the 28-day treatment period, all migraineurs had daily treatment sessions, while HC received no treatment. With the reference electrode placed at Cz and the active electrode at Oz of the 10–20 EEG electrode placement system, participants self-applied anodal tDCS over the visual cortex using a one-channel stimulator (DCSTIMULATOR PLUS, NeuroConn, Ilmenau, Germany). All participants were trained at the baseline visit to use the device and demonstrated the instructors that they were able to use it themselves. Besides, they received an instruction manual. The current densities of the focal electrode and the reference electrode were estimated at 0.029 mA/cmEach tDCS treatment session had a duration of 20 min. The stimulator maintained an intensity of 1 mA for the whole 20 min in patients receiving active tDCS and for 30 s in the sham group. During the remaining 19.5 min of the stimulation in the sham tDCS group, the device intermittently performed impedance checks suggestive of continued stimulation.Migraineurs could use acute treatment as needed; however, changing the prophylactic medication during the study period was not permitted.