Dysmenorrhea subtypes exhibit differential quantitative sensory assessment profiles

Abstract

Women who develop bladder pain syndrome (BPS), irritable bowel syndrome, or dyspareunia frequently have an antecedent history of dysmenorrhea. Despite the high prevalence of menstrual pain, its role in chronic pelvic pain emergence remains understudied. We systematically characterized bladder, body, and vaginal mechanical sensitivity with quantitative sensory testing in women with dysmenorrhea (DYS, n = 147), healthy controls (HCs) (n = 37), and women with BPS (n = 25). Previously, we have shown that a noninvasive, bladder-filling task identified a subset of women with both dysmenorrhea and silent bladder pain hypersensitivity, and we repeated this to subtype dysmenorrhea sufferers in this study (DYSB; n = 49). DYS, DYSB, and BPS participants had lower vaginal mechanical thresholds and reported more pain to a cold stimulus during a conditioned pain modulation task and greater pelvic examination after-pain than HCs (P's < 0.05). DYSB participants also had reduced body mechanical thresholds and less conditioned pain modulation compared to HCs and DYS participants (P's < 0.05). Comparing quantitative sensory testing results among the DYS and HC groups only, provoked bladder pain was the only significant predictor of self-reported menstrual pain (r = 0.26), bladder pain (r = 0.57), dyspareunia (r = 0.39), and bowel pain (r = 0.45). Our findings of widespread sensory sensitivity in women with dysmenorrhea and provoked bladder pain, much like that observed in chronic pain, suggest a need to study the trajectory of altered mechanisms of pain processing in preclinical silent visceral pain phenotypes to understand which features convey inexorable vs modifiable risk.

Figure 1.

Recruitment Flow Chart

Figure 2:. Participants with dysmenorrhea and bladder pain hypersensitivity report pain comparable to participants with bladder pain syndrome.

Participants in each of the 4 groups rated their bladder pain across cystometric thresholds. Box plots indicate median, 25 ^th and 75^th percentile. * indicates worse compared to healthy controls (p < 0.05). HC: Healthy Control, DYS: Dysmenorrhea only, DYSB: DYS + Bladder pain sensitivity, BPS: Bladder Pain Syndrome, VAS: Visual Analogue Scale.

Figure 3:. Dysmenorrhea (DYS and DYSB) and BPS are associated with decreased vaginal pressure pain thresholds (PPTs) and more after-pain.

Numbers designate vaginal positions relative to a clockface (12, under bladder; 7 and 5, iliococcygeus; 6 anorectal raphe). Five minutes after PPTs, after-pain was rated on a 0-10 NRS. * indicates worse compared to healthy controls (p < 0.05). # indicates worse compared to dysmenorrhea-only participants (p < 0.05). HC: Healthy Control, DYS: Dysmenorrhea only, DYSB: DYS + Bladder pain sensitivity, BPS: Bladder Pain Syndrome.

Figure 4:. Dysmenorrhea with provoked bladder pain hypersensitivity is associated with widespread alterations in bodily somatic sensitivity.

PPTs were obtained twice at each of the four locations above. * indicates worse compared to healthy controls (p < 0.05). # indicates worse compared to dysmenorrhea-only participants (p < 0.05). HC: Healthy Control, DYS: Dysmenorrhea only, DYSB: DYS + Bladder pain sensitivity, BPS: Bladder Pain Syndrome. NRS: Numeric Rating Scale, CPM: Conditioned Pain Modulation.

Figure 5:. Provoked bladder pain ratings correlate with self-reported pelvic pain over the past week.

Each data point represents one participant divided by group status (DYS vs DYSB). Locally weighted scatterplot smoothed lines demonstrate the relationship between provoked bladder pain (0-100 VAS) and self-reported urination pain (top), bowel pain (middle) or coital pain (bottom) over the past week (0-100 VAS). DYS: Dysmenorrhea only, DYSB: DYS + Bladder pain sensitivity, VAS: Visual Analog Scale.