PURPOSE: Multiple studies have demonstrated that in healthy subjects painful stimuli applied to one part of the body inhibit pain sensation in other parts of the body, a phenomenon referred to as conditioned pain modulation (CPM).
CPM is related to the presence of endogenous pain control systems. Studies have demonstrated deficits in CPM-associated inhibition in many, but not all chronic pain disorders. The present study sought to determine whether CPM was altered in subjects with Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS).
METHODS AND MATERIALS: Female subjects with and without the diagnosis of IC/BPS were studied psychophysically using quantitative cutaneous thermal, forearm ischemia and ice water immersion tests. CPM was assessed by quantifying the effects of immersion of the hand in ice water (conditioning stimulus) on threshold and tolerance of cutaneous heat pain (test stimulus) applied to the contralateral lower extremity.
RESULTS: CPM responses of the subjects with IC/BPS were statistically different from those of healthy control subjects for both cutaneous thermal threshold and tolerance measures. Healthy control subjects demonstrated statistically significant increases in their thermal pain tolerances whereas subjects with the diagnosis of IC/BPS demonstrated statistically significant reductions in their thermal pain tolerances.
CONCLUSIONS: An endogenous pain inhibitory system normally observed with CPM was altered in subjects with IC/BPS. This identifies IC/BPS as similar to several other chronic pain disorders such as fibromyalgia and irritable bowel syndrome and suggests that a deficit in endogenous pain inhibitory systems may be a contributor to such chronic pain disorders.
Ness TJ, Lloyd LK, Fillingim RB. Are you the author?
Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, AL.
Reference: J Urol. 2013 Aug 20. pii: S0022-5347(13)05144-6.