The concept of “pain biomarkers” is sometimes used when discussing future treatment perspectives, 8 since control based on reported pain perception depends on the subjectivity of each patient, even when evaluated using multidimensional scales. 2, 4, 5 Other techniques investigated in treating pain include cranial electrotherapy stimulation (CES), transcranial random noise stimulation (tRNS) and reduced impedance non-invasive cortical electrostimulation (RINCE). 2 Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) techniques are currently recommended for treating certain conditions such as fibromyalgia, neuropathic pain, complex regional pain syndrome and migraine, presenting low to moderate analgesic effect and without serious adverse events. Non-invasive brain stimulation (NIBS) has been extensively studied for the past 30 years in controlling chronic pain. 2 Despite advancement in available therapeutic resources, there is still no consensus on the mechanisms underlying the development and maintenance of pain. Based on this literature, evidence suggests that BE may not only be useful for acute and persistent pain, but also for a variety of chronic pain states in which opioids are not effective.Ĭhronic pain affects 28% to 50% of the world population and its treatment remains a challenge, 1 with up to 30% of cases being resistant to drug treatment. There is limited evidence on the dosage of beta-endorphin in chronic pain conditions during treatment with NIBS. The studies in this scoping review ranged from unsatisfactory to good based on the adopted criteria, with no study achieving an excellent rating. The study design, sample size, stimulation type, session protocol and the main findings of each study were extracted. A total of 67 of 73 references were excluded, and 6 identified studies met the inclusion criteria.
The results are described in a narrative form grouped by pain condition, type of intervention, stimulation protocol, outcome measures and main results. Content analysis was applied and summarized. Independent reviewers determined if the article met the study criteria at each stage for it to be included. A scoping review to synthesize evidence and assess articles describing the use of beta-endorphins as a pain biomarker in chronic pain patients treated with non-invasive brain stimulation techniques was systematically performed with respect to the study quality, the technique employed and the results.