Cortical and Psychological Mechanisms of Visceral Pain

Dysmenorrhea is an incapacitating type of visceral pain that affects numerous menstruating women and is defined by painful menstrual cramps and often occurs in the absence of pelvic pathology. Women with dysmenorrhea have reported higher sensitivity to experimental pain, and vulnerability to pain sensitivity may be a primary risk factor for developing chronic pelvic pain for women with dysmenorrhea. Cross-organ sensitization (COS), or the theory that uterine inflammation during menstruation can contribute to chronic pelvic pain by generating neurogenic inflammation in other organs, may be a primary mechanism associated with pelvic pain in women with dysmenorrhea. Dysmenorrhea sufferers with cross-organ sensitization (D+COS), compared to those without COS, are theorized to experience higher rates of chronic visceral pain and are more susceptible to experimentally-induced pain. The implications of long-term pain sensitivity have been theorized to increase susceptibility to other chronic, visceral pain conditions, and these conditions are associated with higher rates of depression and other mood disorders. Frontal activity during pain has been linked to attentional processing, with both the right and left dorsolateral prefrontal cortices (dlPFC) negatively correlated with intensity perception and unpleasantness. However, most visceral pain research has focused on gastrointestinal disorders, making it important to identify pain mechanisms in women with dysmenorrhea. Since dysmenorrhea, depression, and somatization are associated with abnormalities in frontal cingulate networks, and given the emerging evidence supporting an association between affect and pain, it is necessary to account for the potential effects on regional brain function that may be associated with co-occurring psychological symptoms in individuals experiencing dysmenorrhea. The results of the present study provide evidence that psychological symptoms and brain activity predict increased levels of visceral pain, specifically for women with dysmenorrhea and cross-organ sensitization (COS). Results showed that somatization, depression, and frontal beta activity account for a significant amount of variance, yet somatization is the only significant link between women suffering from D+COS and bladder pain. Thus, based on these results, somatization emerged as the candidate risk factor for developing chronic pelvic pain, and somatic symptoms should be considered a primary target for prevention and intervention strategies.

Rebecca Silton, Ph.D., Kevin Hellman, Ph.D.