Mechanisms of peripheral sensitization in endometriosis patients with peritoneal lesions and acyclical pain

The connection between endometriosis and secondary dysmenorrhea

Endometriosis (EMS) is a prevalent gynecological condition characterized by the presence of endometrial tissue outside the uterus, often leading to secondary dysmenorrhea (SD), chronic pelvic pain and infertility. This review explores the intricate connection between EMS- associated pain and SD, focusing on the pathophysiological mechanisms underlying dysmenorrhea in EMS. Key contributors to pain include inflammation, aberrant immune responses, neurogenic inflammation, peritoneal irritation, peripheral sensitization, central sensitization and cross-organ sensitization. Understanding the pain pathways in EMS highlights the complexity of symptom manifestation and underscores the necessity for a multidisciplinary approach to management. Clinical manifestations, including chronic pelvic pain, dyspareunia, infertility, gastrointestinal and bladder symptoms, fatigue and malaise, are discussed, emphasizing the diverse impact of EMS on women's health. Various treatment modalities, ranging from pharmacological interventions to surgical and complementary approaches, are outlined to provide comprehensive management strategies for EMS-related menstrual pain/SD. This review aims to enhance understanding and facilitate the effective management of EMS-associated SD, ultimately improving the quality of life for affected individuals.

Pain from Internal Organs and Headache: The Challenge of Comorbidity

Headache and visceral pain are common clinical painful conditions, which often co-exist in the same patients. Numbers relative to their co-occurrence suggest possible common pathophysiological mechanisms. The aim of the present narrative review is to describe the most frequent headache and visceral pain associations and to discuss the possible underlying mechanisms of the associations and their diagnostic and therapeutic implications based on the most recent evidence from the international literature. The conditions addressed are as follows: visceral pain from the cardiovascular, gastrointestinal, and urogenital areas and primary headache conditions such as migraine and tension-type headache. The most frequent comorbidities involve the following: cardiac ischemic pain and migraine (possible shared mechanism of endothelial dysfunction, oxidative stress, and genetic and hormonal factors), functional gastrointestinal disorders, particularly IBS and both migraine and tension-type headache, primary or secondary dysmenorrhea and migraine, and painful bladder syndrome and headache (possible shared mechanisms of peripheral and central sensitization processes). The data also show that the various visceral pain-headache associations are characterized by more than a simple sum of symptoms from each condition but often involve complex interactions with the frequent enhancement of symptoms from both, which is crucial for diagnostic and treatment purposes.

Evaluating the Correlation between Myofascial Pelvic Pain and Female Sexual Function: A Prospective Pilot Study

Introduction: Myofascial pelvic pain (MFPP) is a prevalent yet frequently overlooked condition characterized by myofascial trigger points located within the pelvic floor muscles. Women with MFPP often experience severely reduced quality of life due to impaired sexual health. Here, we examined the relationship between MFPP and sexual function. Materials and Methods: Eighty-three women with a benign gynecological condition were included in this pilot study. For each patient, we obtained a complete medical history, measured different types of subjective pain intensity using a visual analog scale, performed a validated standardized examination of the pelvic floor muscles for measuring MFPP, and used the German Female Sexual Function Index (FSFI-d) questionnaire. Results: Compared to women without MFPP (46 out of 83; 55.4%), the women with MFPP (37 out of 83; 44.6%) reported experiencing pain on more days per month (8 vs. 3 days/month; p = 0.002) and higher median VAS scores for dyspareunia (4 vs. 0; p < 0.001). We also found a significant inverse correlation between the severity of MFPP and overall FSFI-d scores (r = -0.35; p < 0.001), particularly in the FSFI-d subdomains of pain (r = -0.364; p < 0.001), lubrication (r = -0.230; p = 0.005), and arousal (r = -0.360; p < 0.001). Conclusions: Due to the higher prevalence of dyspareunia and pelvic pain, MFPP significantly impacts several aspects of female sexual health and function. This information, combined with increased awareness regarding MFPP, may provide a foundation for designing individualized therapies, thereby improving the quality of life of women affected by MFPP.

Nerve Bundle Density and Expression of NGF and IL-1β Are Intra-Individually Heterogenous in Subtypes of Endometriosis

Endometriosis is a gynecological disorder associated with local inflammation and neuroproliferation. Increased nerve bundle density has been attributed to increased expression of nerve growth factor (NGF) and interleukin-1β (IL-1β). Immunohistochemical analysis was carried out on 12 patients presenting with all three anatomic subtypes of endometriosis (deep, superficial peritoneal, endometrioma) at surgery, with at least two surgically excised subtypes available for analysis. Immunolocalization for nerve bundle density around endometriosis using protein gene product 9.5 (PGP9.5), as well as NGF and IL-1β histoscores in endometriosis epithelium/stroma, was performed to evaluate differences in scores between lesions and anatomic subtypes per patient. Intra-individual heterogeneity in scores across lesions was assessed using the coefficient of variation (CV). The degree of score variability between subtypes was evaluated using the percentage difference between mean scores from one subtype to another subtype for each marker. PGP9.5 nerve bundle density was heterogenous across multiple subtypes of endometriosis, ranging from 50.0% to 173.2%, where most patients (8/12) showed CV ≥ 100%. The percentage difference in scores showed that PGP9.5 nerve bundle density and NGF and IL-1β expression were heterogenous between anatomic subtypes within the same patient. Based on these observations of intra-individual heterogeneity, we conclude that markers of neuroproliferation in endometriosis should be stratified by anatomic subtype in future studies of clinical correlation.

Overview: Chronic Pain and Cannabis-Based Medicines

Chronic pain is primarily conceptualized as a disease in its own right when it is associated with emotional distress and functional impairment. Pathophysiologically, dysfunction of the cortico-mesolimbic connectome is of major importance, with overlapping signals in the nociceptive and stress systems. The endocannabinoid system plays an important role in the central processing of nociceptive signals and regulates the central stress response. Clinically, there is moderate evidence that cannabis-based medicines (CBM) can contribute to a significant reduction in pain, especially the associated pain affect, and improvement in physical function and sleep quality in a proportion of patients with chronic pain. The analgesic effect appears to be largely independent of the cause of pain. In this context, CBM preferentially regulates stress-associated pain processing.

CGRP neuropeptide levels in patients with endometriosis-related pain treated with dienogest: a comparative study

BACKGROUND AND OBJECTIVE

Endometriosis (EM) involves the peripheral nervous system and causes chronic pain. Sensory nerves innervating endometriotic lesions contribute to chronic pain and influence the growth phenotype by releasing neurotrophic factors and interacting with nearby immune cells. Calcitonin gene-related peptide (CGRP), a pain-signaling neurotransmitter, has a significant role. This study examines the effect of Dienogest (DNG), a hormone therapy used for managing EM -related pain, on serum CGRP levels in EM patients.

MATERIALS AND METHODS

The Visual Analog Scale (VAS) assessed pain in diagnosed EM.

INDIVIDUALS

Serum samples were obtained to measure CGRP concentration. Participants received a 2 mg/day oral dose of DNG for six months as prescribed treatment. Additional serum samples were collected after this period to measure CGRP levels.

RESULTS

In the EM group, 6.7%, 33.3%, and 20% had ovarian EM, ovarian plus uterosacral, and ovarian plus bladder, respectively. The EM group showed higher CGRP serum levels than the control group (80.53 ± 16.13 vs. 58.55 ± 6.93, P < 0.0001). Still, after drug administration, CGRP serum levels significantly decreased compared to pre-treatment levels (69.66 ± 11.53 vs. 80.53 ± 16.13, P < 0.05). The EM group showed higher pain compared to the control group (7.93 ± 1.58 vs. 0.13 ± 0.35, P < 0.0001), but after drug administration, pain significantly decreased compared to pre-treatment levels (1.00 ± 2.00 vs. 7.93 ± 1.58, P < 0.05).

CONCLUSION

DNG administration reduces pain and serum CGRP levels in EM patients, offering the potential for innovative treatments and tailored options. Understanding neurotransmitter roles and drug effects can aid in discovering more effective modulators for these pathways.

Distribution of Nerve Fibers in Abdominal Wall Endometriosis and Their Clinical Significance

Objective

This study aimed to explore the distribution of nerve fibers in abdominal wall endometriosis (AWE) and discern their association with pain.

Methods

A retrospective case-control study was conducted. The cases comprised 30 patients diagnosed with AWE, while the control group consisted of 17 patients who had undergone laparotomy without any history of endometriosis. We analyzed clinical characteristics and examined the innervation patterns in samples using stains for S-100, neuron-specific enolase (NSE), protein gene product 9.5 (PGP9.5), neurofilament (NF), and substance P (SP) antibodies.

Results

There was a notable increase in the density of S-100, NSE and PGP9.5 immunoreactive nerve fibers and a higher proportion of SP positivity in AWE lesions compared to standard abdominal wall scars (p < 0.05). However, there were no significant differences in the density or proportion of NF-immunoreactive nerve fibers between the cases and the controls. Moreover, no statistically significant correlation was observed between the density of S-100, NSE, PGP9.5, NF, or SP-positive nerve fibers and pain scores.

Conclusion

This study demonstrated an increased immunoreactive nerve fiber density located in AWE lesions compared to normal abdominal wall scars. Further high-quality studies are needed to investigate the mechanisms responsible for pain in women with endometriosis.