Extra-Low Voltage and Limited Total Energy Approaches to Increase Patient Comfort and Safety During Transcranial Direct Current Stimulation

Abstract

Transcranial Direct Current Stimulation (tDCS) is a non-invasive brain stimulation technique aiming to polarize brain tissue in order to elicit modulating effects on cortical activity. During tDCS, weak constant current is applied across the brain through surface electrodes which are attached to the scalp. tDCS has shown promising therapeutic effects in a range of neurological conditions and is being evaluated for therapeutic use in epilepsy, major depression, chronic pain, stroke rehabilitation and more. Though tDCS is a generally well tolerated treatment option, there is room for improvement of patient safety and comfort. During tDCS, current is constant and skin-electrode impedance is strongly dynamic. Thus, compliance voltage is also dynamic. Skin-electrode impedance may be influenced through choice of electrode type and the way of electrode preparation prior to treatment. High impedance and voltage during tDCS can co-induce skin burns at the electrode sites. Here, feasibility of reduced (peak) voltage tDCS is investigated and presented alongside a rather protective and advanced new approach for voltage and current control during tDCS. According to the results, the maximum stimulator output voltage may be reduced significantly in the most common tDCS paradigms without affecting stimulation intensity and efficacy. Optimized electrode preparation combined with reduced maximum stimulator output voltage and intelligent current waveforms is considered a viable contribution towards more safe, protective and reliable brain stimulation paradigms, especially avoiding the occurrence of skin lesions after multiple stimulation treatments.