Central sensitization in women with endometriosis: a cross-sectional study

Pain is the primary symptom of endometriosis and may progress into a chronic, acyclic condition driven by neuroinflammatory mechanisms, leading to neuropathic and ultimately nociplastic pain. Central sensitization, a form of nociplastic pain, is associated with various chronic pain syndromes collectively known as Central Sensitivity Syndromes, such as fibromyalgia and irritable bowel syndrome. These central mechanisms may contribute to treatment failure and symptom recurrence in endometriosis, significantly impacting quality of life. The Central Sensitization Inventory (CSI), initially validated in patients with fibromyalgia, has demonstrated utility in identifying central sensitization in those with endometriosis. The primary outcome of this study was to assess the prevalence of central sensitization in patients with a diagnosis of endometriosis/adenomyosis. The secondary objective was to evaluate the association between the patient's demographic and clinical characteristics and the diagnosis of central sensitization syndrome.

This was a single-center, observational, cross-sectional study. Between February 1, 2023, and August 31, 2023, we prospectively enrolled 142 patients with a diagnosis of endometriosis/adenomyosis, as determined by surgery/ultrasound, who attended the "Endometriosis and Pelvic Pain" unit within the Obstetrics and Gynecology Clinic in Udine. Demographic and clinical data were collected. The prevalence of central sensitization was assessed using a validated questionnaire, the Central Sensitization Inventory. A CSI score ≥ 40 was considered as an indicator of Central Sensitization Syndrome.

The prevalence of CS was 52.1%. Among the clinical characteristics, only dyspareunia and vulvodynia were significantly associated with CS in our patients (p < 0.001), while other symptoms and even the type of endometriosis were not. However, a significant association was found with the onset of symptoms being more than 5 years, compared to earlier-onset forms (p < 0.001). A strong association was also found between positive CSI and overlap syndromes.

Given the high prevalence of central sensitization based on the CSI among this tertiary-referral cohort, identifying it precociously might be useful for counseling patients and choosing a multimodal treatment in addition to conventional strategies. Further studies are needed to confirm these findings in broader and non-selected populations and to validate the applicability of the CSI questionnaire as a screening tool for central sensitization in common practice.