Non-invasive transcranial stimulation of the brain in patients with pain

Many neurological diseases are characterized by pain as a key symptom. Systematic studies to investigate the mechanisms of pain are of outmost importance, since they may subsequently result in improved treatment strategies. In recent years, possibilities have emerged to manipulate ongoing neuroplastic changes by external modulation, either by interfering with neuronal firing rate or with neuronal membrane potentials. The first can be performed by repetitive transcranial magnetic stimulation (rTMS), the latter by direct current stimulation (tDCS). rTMS is a technology which uses electromagnetic principles to produce small electrical currents in the cortex. Evidence indicates that rTMS-produced plastic changes in the CNS are observable at both the cellular and functional levels. It is proposed by many studies that rTMS can provide short-term relief in chronic pain. tDCS as a tool aims to induce prolonged neuronal excitability and activity alterations in the human brain via alterations of the neuronal membrane potential. Apart from its impressive persistent excitability effects, it is a non-invasive method and can be applied painlessly. Accordingly, tDCS in the human is a promising tool in the treatment of diseases that are accompanied by changes of cortical excitability.