A review on mismatch negativity in chronic pain

Chronic pain impacts millions worldwide, and places a significant strain upon healthcare systems, yet current treatments are largely suboptimal. Multiple studies have noted differences in various event-related potentials (ERP) in patients with chronic pain, and one of the primary ERP components of interest is mismatch negativity (MMN). It is currently not established whether alterations in MMN is a biomarker of chronic pain. The aim of this review is to assess how MMN is altered in patients with chronic pain. We carried out a systematic search of Embase, Medline and PubMed databases with the terms 'chronic pain' and 'mismatch negativity' and found seventeen studies. Seven screened studies were included in the final review. Of these, one cohort underwent experimentally induced chronic pain, whereas the other cohorts had a range of chronic pain conditions. Five studies measured magnitude of MMN responses, whilst two focused on latency. Three studies found smaller amplitudes in chronic pain, and both studies found longer latency. Both the studies with larger MMN reported that it was due to increased attention to the pain. In conclusion, this (first) literature review on MMN in chronic pain found that these studies offered wide-ranging applications of MMN, from understanding the neural pathophysiology of chronic pain to therapeutic advances. Given the limited number of studies and unexplored effect of pain medication on MMN, more studies are required to establish if MMN is a reliable pharmacodynamic marker of chronic pain.