Exploring the Relationship Between Temporal Summation and Conditioned Pain Modulation in Patients After Surgery – A Preliminary Investigation

Temporal summation of pain (TSP) and conditioned pain modulation (CPM) are commonly used psychophysical paradigms to investigate pro- and antinociceptive aspects of endogenous pain modulation, and are putative phenotypic contributors to the risk for the development of chronic pain. Studies comparing the relationship between the two paradigms have largely been conducted in healthy controls; however, research is warranted in chronic pain populations. The current study measured TSP and CPM in 38 individuals who underwent surgery within the previous 24 months (89% female, ages 14-59 years) and 45 healthy pain-free controls (71% female, ages 15-62 years), and assessed the correlations between these two paradigms. In line with published protocols, TSP was performed using Von Frey filaments. For the CPM paradigm, pressure pain threshold of the non-dominant trapezius was used as the test stimulus and the dominant hand in an ice bath was used as the conditioning stimulus. Results of Wilcoxon Signed Rank Tests showed significant increased pain rating for TSP during repetitive stimuli (p<.001), and between baseline and conditioning for CPM (p=.002). Results of a Spearman’s correlation revealed approaching significance association between TSP and CPM in the patient group, but not in controls. Preliminary findings may suggest distinct aspects of central pain processing of this cohort and contribute to our understanding regarding the methodology and interpretation of these paradigms in clinical pain populations. Data collection is ongoing, further investigations with larger sample size will be conducted to verify the current findings. Funded by National Institutes of Health (R35GM142676–01).