Conditioned pain modulation in people living with HIV (PLWH) is ineffective in comparison to healthy controls, found Owens et al. in their study published this year.
Three groups were compared: PLWH with chronic pain, PLWH without chronic pain and healthy controls. Pain modulation was assessed through mechanical temporal summation (TS), heat TS at three different temperatures: 46, 48, and 50°C, and CPM with pressure pain thresholds as test stimuli, and cold pressor as conditioning.
The authors found that mechanical TS was significantly greater in PLWH with chronic pain as compared to the PLWH without chronic pain or controls. Similarly, PLWH with chronic pain also had significantly more wind-up than both other groups at temperatures of 46 and 48 °C in the heat TS paradigm, though not at 50°C. Interestingly, both groups of PLWH showed no significant CPM effect, while the controls did. Controls significantly differed in their CPM effect from PLWH.
PLWH with chronic pain had significant correlation between average pain severity and mechanical TS.
These changes in pain modulation may signal vulnerability for developing chronic pain in PLWH, however more mechanistic research in this field is warranted.
Medoc’s AlgoMed was used in the CPM paradigm, and Medoc’s TSA-II was used for the heat TS paradigm.
Citation: Owens, Michael A., Romy Parker, Rachael L. Rainey, Cesar E. Gonzalez, Dyan M. White, Anooshah E. Ata, Jennifer I. Okunbor, Sonya L. Heath, Jessica S. Merlin, and Burel R. Goodin. “Enhanced facilitation and diminished inhibition characterizes the pronociceptive endogenous pain modulatory balance of persons living with HIV and chronic pain.” Journal of neurovirology 25, no. 1 (2019): 57-71.
Link to the abstract: https://www.ncbi.nlm.nih.gov/pubmed/30414048