Evaluation of a scoring system for the detection of central sensitization among women with chronic pelvic pain

Abstract

Background: Central sensitization is frequently associated with chronic pelvic pain and requires specific management. The pain is described as hypersensitivity to an innocuous stimulus that is both widespread and persistent. However, no study has evaluated if central sensitization can be measured objectively with neurophysiological tests in the pelvic and perineal area to prove this concept in women with chronic pelvic pain.

Objective: This study aimed to evaluate nociceptive thresholds (primary objective) and spatial and temporal diffusion of pain among women with chronic pelvic pain and high or low scores of central sensitization.

Study design: This prospective, assessor-blinded, comparative study compared a cohort of women with chronic pelvic pain and a high (>5/10; n=29) vs low (<5/10; n=24) score of sensitization according to the Convergences PP criteria. Participants underwent a noninvasive bladder sensory test, a rectal barostat test, and a muscular (algometer) and a vulvar (vulvagesiometer) sensory test. Poststimulation pain (minutes), quality of life (Medical Outcomes Study 36-Item Short Form Survey), and psychological state, comprising anxiety (State-Trait Anxiety Inventory), depression (Beck Depression Inventory Short Form), and catastrophizing (Pain Catastrophizing Scale), were assessed.

Results: The participants mostly suffered from endometriosis (35.8%), irritable bowel syndrome (35.8%), bladder pain syndrome (32.1%), and vestibulodynia (28.3%). Baseline characteristics were similar. Women with a high sensitization score had more painful diseases diagnosed (2.7±1.3 vs 1.6±0.8; P=.002) and suffered for longer (11±8 vs 6±5 years; P=.028) than participants with a low score. The bladder maximum capacity was equivalent between participants (399±168 vs 465±164 mL; P=.18). However, the pain felt at each cystometric threshold was significantly increased in women with a high sensitization score. No difference was identified for the rectal pain pressure step (29.3±5.5 vs 30.7±6.5 mm Hg; P=.38). Rectal compliance was decreased in women with a high sensitization score with a considerable increase in pain felt. The average of pain pressure thresholds at the 5 vulvar sites tested was decreased in these participants (162.5±90.5 vs 358.7±196.5 g; P=.0003). Similar results were found for the average of the pain pressure thresholds at 6 muscles tested (1.34±0.41 vs 2.63±1.52 kg/m²; P=.0002). A longer period was needed for patients with high sensitization score to obtain a VAS <3 out of 10 after the stimulation of the bladder (4.52±5.26 vs 1.27±2.96 minutes; P=.01), the rectum (3.75±3.81 vs 1.19±1.23 minutes; P=.009), and the muscles (1.46±1.69 vs 0.64±0.40 minutes; P=.002). The psychological state was equivalent between groups. No association was found between the sensory thresholds and the psychological state results. The physical component of the quality of life score was reduced in women with high sensitization score (P=.0005), with no difference in the mental component.

Conclusion: Using neurophysiological tests, this study showed that there are objective elements to assess for the presence of central sensitization, independently of psychological factors.

Trial registration: ClinicalTrials.gov NCT03541954.

Keywords: Convergences PP score; algometer; central sensitization; chronic pelvic pain; endometriosis; pain threshold; visceral pain.