Home-based Transcranial Stimulation in the Treatment of Patients With Refractory Chronic Pain

Refractory chronic pain represents a serious and limiting health condition which does not respond to standard pharmacological therapy. Thus, it emerges the necessity of new techniques to treat these group of diseases, such as the transcranial electrical stimulation (tES). This procedure induces a low-intensity electrical current through the scalp to modify the excitability of brain cells, thus facilitating changes in neural networks which may be dysfunctional in some chronic pain patients. The main objective of this research is to test the efficacy of two tES techniques, differentiated by applying direct or alternant electrical current, to reduce the pain intensity and to increase pain thresholds of these patients. Besides, intervention is implemented at home for patients themselves thanks to a portable and convenient stimulator device, after one training session provided by technicians. Researches can supervise the compliance of the treatment remotely, as the stimulator has a permanent connection with their computers. A home-based approach means a more comfortable and accessible treatment alternative for patients, since they do not have to attend to clinics everyday to receive the stimulation; the advantages become even more relevant in the pandemic context, since the risk of being infected is radically minimized. Despite the main purpose is to test the efficacy of tES to improve the pain suffered by patients, many other areas are considered as secondary end points for being intrinsically linked or affected by the disease, such as the interference in daily tasks provoked by pain, mood disorders (depression/anxiety), fatigue, life quality, physical functioning and sleep quality; these last two variables are measured with actigraph wristwatches, apart from specific questionnaires. Lastly, endogenous modulatory pain mechanisms are examined through sensory tests, namely Conditioned Pain Modulation and Temporal Summation of pain.