Investigation of the impact of central sensitization mechanism, which may develop due to chronic pelvic pain associated with endometriosis, on nerves and neural networks in the brain's pain centers

ABSTRACT INVESTIGATION OF THE IMPACT OF CENTRAL SENSITIZATION MECHANISM, WHICH MAY DEVELOP DUE TO CHRONIC PELVIC PAIN ASSOCIATED WITH ENDOMETRIOSIS, ON NERVES AND NEURAL NETWORKS IN THE BRAIN'S PAIN CENTERS AIM: Evaluation of Structural and Functional Characteristics of Brain Pain Centers Using Magnetic Resonance Imaging in Patients with Endometriosis and Chronic Pelvic Pain MATERIAL AND METHODS: Between June 2022 and September 2023, the medical records of patients who applied to the Gynecology Outpatient Clinic and/or were hospitalized in the Gynecology Department at Istanbul University-Cerrahpaşa, Cerrahpaşa Medical Faculty, Department of Obstetrics and Gynecology were retrospectively reviewed. The records of endometriosis patients aged 18-45 who underwent brain magnetic resonance imaging (MRI) and women of similar age and body mass index without gynecological pathology were examined. A total of 30 patients were divided into 3 groups: 1. patients with chronic pelvic pain and deep infiltrating endometriosis (10 patients), 2. patients with cystic endometriosis (ovarian endometriomas) without chronic pelvic pain (10 patients), 3. women of similar age and body mass index without gynecological pathology who were under routine outpatient follow-up (10 women). According to the file data, the following characteristics of the patients were recorded and compared: anamnesis information, examination findings, laboratory and imaging results, and for those who underwent surgery, operative notes and pathology results. RESULTS: In patients diagnosed with Deep Infiltrating Endometriosis, a statistically significant reduction in gray matter volume was detected in the right superior-middle temporal gyrus (p-FWE-corrected: 0.003) and left putamen (p-FWE-corrected: 0.01) regions compared to the healthy control group. In patients diagnosed with Cystic Endometriosis, no brain region showed a statistically significant difference in gray matter volume compared to the healthy control group. In patients diagnosed with Deep Infiltrating Endometriosis, a statistically significant reduction in gray matter volume was detected in the right posterior insula region compared to patients diagnosed with Cystic Endometriosis (p-FWE-corrected=0.018). In patients diagnosed with Deep Infiltrating Endometriosis, compared to healthy control women, there was a statistically significant increase in resting-state functional connectivity between the amygdala and the right frontal pole (p-FWE-corrected: 0.012000, p-FWE-corrected: 0.043800), the left paracingulate gyrus (p-FWE-corrected: 0.036000), the right frontal operculum cortex (p-FWE-corrected: 0.039800), and the anterior region of the cingulate gyrus (p-FWE-corrected: 0.044000). Additionally, in these patients, compared to healthy controls, there was a statistically significant increase in resting-state functional connectivity between the posterior region of the cingulate gyrus and the precuneus cortex (p-FWE-corrected: 0.002400). Conversely, in patients diagnosed with Deep Infiltrating Endometriosis, there was a statistically significant decrease in resting-state functional connectivity between the anterior region of the cingulate gyrus and the posterior region of the left middle temporal gyrus (p-FWE: 0.002256) compared to healthy controls. In patients diagnosed with Cystic Endometriosis, compared to healthy control women, no statistically significant changes were found in resting-state functional connectivity, measured using the seed-to-voxel method, between the anterior and posterior regions of the cingulate gyrus, the insula, the thalamus, and the amygdala with other brain areas. CONCLUSION: In patients with endometriosis and chronic pelvic pain, brain imaging revealed structural changes characterized by a reduction in gray matter volume in the right superior-middle temporal gyrus, the left putamen, and the right posterior region of the insula. Functional connectivity analyses showed an increase in connectivity between the amygdala and cingulate gyrus centers with other brain pain centers, while a decrease in connectivity was observed in the anterior region of the cingulate gyrus. Keywords: chronic pelvic pain, endometriosis, brain pain centers, gray matter volume, functional connectivity