Pain Sensitization in Male Chronic Pelvic Pain Syndrome: Why Are Symptoms so Difficult to Treat?

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Abstract
Purpose: Male chronic pelvic pain syndrome (CPPS) is a chronic and debilitating symptom complex, and inconsistent outcomes of antibiotic and anti-inflammatory treatments have created an interest in investigating the neurological mechanisms of CPPS pain. Because chronic pelvic pain likely results in hyperexcitability of dorsal horn neurons, ie central sensitization, thermal algometry may be useful in the assessment of CPPS. We evaluated men with and without CPPS to determine if there were differences between the 2 groups in their responses to noxious heat stimuli. Materials and Methods: We recruited 66 healthy men without CPPS and 36 men with a history of CPPS for the study. Mean age of CPPS subjects was 43.1 years (range 18 to 62) and mean age of controls was 35.1 (range 21 to 61). All subjects with pain completed a National Institutes of Health-Chronic Prostatitis Symptom Index. We conducted thermal sensory tests with a small thermode programmed to deliver 2 series of 4 rapid bursts of noxious heat stimuli to the perineum and the anterior thigh. The subjects reported sensation on a computerized visual analog scale (COVAS) with a manual sliding lever. The average peak COVAS values and time to peak values from thigh and perineum of each series of thermal bursts were compared between CPPS and controls. Results: The mean pain score on questionnaires was 9.7 (4 or greater indicating significant pain), mean urinary score was 4.7 (range 0 to 10) and mean quality of life impact score was 7.3 (range 3 to 13). Compared to controls men with CPPS reported higher mean peak COVAS values in the perineum. There was no difference between groups in the peak COVAS value on the thigh. Conclusions: Men with CPPS have altered heat sensation/pain sensitization in the perineum compared to controls. This finding is another that supports the resemblance of CPPS to other chronic pain syndromes and may help explain why CPPS is often refractory to treatment. Further investigations into male CPPS should focus on the mechanisms inducing and maintaining pain in an effort to treat this condition effectively.