Non-invasive transcranial direct current stimulation for the study and treatment of neuropathic pain

In the last decade, radiological neuroimaging techniques have enhanced the study of mechanisms involved in the development and maintenance of neuropathic pain. Recent findings suggest that neuropathic pain in certain pain syndromes (e.g., complex regional pain syndrome/reflex sympathic dystrophy, phantom-limb pain) is associated with a functional reorganization and hyperexitability of the somatosensory and motor cortex. Studies showing that the reversal of cortical reorganization in patients with spontaneous or provoked pain is accompanied by pain relief stimulated the search for novel alternatives how to modulate the cortical excitability as a strategy to relieve pain. Recently, non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) were proposed as suitable methods for modulation of cortical excitability. Both techniques (TMS and tDCS) have been clinically investigated in healthy volunteers as well as in patients with various clinical pathologies and variety of pain syndromes. Although there is less evidence on tDCS as compared with TMS, the findings on tDCS in patients with pain are promising, showing an analgesic effect of tDCS, and observations up to date justify the use of tDCS for the treatment of pain in selected patient populations. tDCS has been shown to be very safe if utilized within the current protocols. In addition, tDCS has been proven to be easy to apply, portable and not expensive, which further enhances great clinical potential of this technique.