Observing electrical brain responses around the nociceptive detection threshold

There is a lack of objective outcome measures for monitoring key neural mechanisms underlying chronic pain, such as central sensitization. Recently, we combined psychophysical Multiple Threshold Tracking (MTT) with evoked potentials (EPs) to study neurophysiological activity related to processing of single- and double-pulse electronociceptive stimuli. Results from pain-free subjects measured at the Technical Medical Center of the University of Twente suggest that the MTT-EP method might be a promising step toward a diagnostic tool for chronic pain patients. A next step is exploration of its replicability in a hospital environment and its behavior in chronic pain patients. We explored the replicability of the MTT-EP method in twenty pain-free subjects (Central Sensitization Inventory (CSI)-score 14.6 ± 8.8) at St. Antonius Hospital. Secondly, we measured nociceptive detection thresholds (NDTs) and EPs from seven failed back surgery syndrome (FBSS) patients (CSI-score 49.0 ± 15.5). Preliminary results show values of NDTs and EPs, habituation and paired-pulse facilitation, which are in line with results from the University of Twente. Again, EPs are modulated by stimulus detection and amplitudes. Strikingly, we found higher NDTs in FBSS patients and EPs appeared modulated by stimulus detection, but not by amplitudes. Since similar phenomena in NDTs and EPs were observed during nociceptive stimulation in pain-free subjects at St. Antonius hospital, it can be concluded that results of MTT-EP method can be replicated. Secondly, the observed altered behavior of NDTs and EPs in FBSS patients showing signs of central sensitization allows further hypotheses regarding responsiveness to mechanisms underlying chronic pain.