A model for radiating leg pain of endometriosis

Neuropelveology for Endometriosis Management: A Systematic Review and Multilevel Meta-Analysis

Background: Despite the availability of treatments such as surgery and hormonal therapy, women with endometriosis often endure chronic problems. This review aims to evaluate the effectiveness and safety of neuropelveology. Methods: In a systematic review with a meta-analysis, we searched three electronic databases: MEDLINE (PubMed), Scopus, Embase, and Web of Science (WOS). The search was conducted in January 2024 with no date or language restrictions using a carefully curated set of keywords. We conducted a comprehensive review, including all observational and clinical trials reporting data on neuropelveology approaches in the management of endometriosis, irrespective of geographical location. The studies included in our review were required to be published in peer-reviewed journals and be available in any language, with at least an abstract in English. The data of all included studies were summarized in excel (version 19) and were analyzed by Comprehensive Meta-analysis v3.3 (Biostat) and STATA (version 17). A multilevel meta-analysis was performed on studies with two arms (intervention and control) to evaluate the efficacy of neuropelveology in managing women with endometriosis. Results: After screening 476 records, 30 studies, published from 1952 to 2021, were included in this review, each employing various methodologies. The studies were divided into the following three categories: (a) efficacy of neurectomy or nerve resection (n = 20), (b) efficacy of neurolysis (nerve blocks) (n = 4), and (c) efficacy of neuromodulation (n = 6) in the management of endometriosis. Among the studies evaluating the efficacy of neurectomy or nerve resection, 10 studies (with 18 group comparisons) were included in the random-effects meta-analysis. Treatment success (not occurrence of pain) was higher with neurectomy vs. controls (RR = 0.497, 95% CI = 0.236 to 1.04, p = 0.06 (for experimental studies) and RR = 0.248, 95% CI = 0.14 to 0.43, p < 0.001 (for observational studies)), representing a 50% and 75.2% risk reduction in the recurrence of pain in experimental and observational studies, respectively. Similarly, neurolysis, particularly superior hypogastric plexus blocks and uterine nerve ethanol neurolysis, demonstrated encouraging outcomes in pain reduction and an improved quality of life for women with endometriosis. The efficacy of neuromodulation in managing endometriosis symptoms appears promising but requires further investigation. Conclusions: In conclusion, neuropelveology approaches, such as neurectomy, neurolysis, and neuromodulation, offer significant potential for pain reduction in endometriosis patients, albeit with risks of complications and high recurrence rates, necessitating careful patient selection and long-term monitoring.

The Unmet Needs for Studying Chronic Pelvic/Visceral Pain Using Animal Models

The different definitions of chronic pelvic/visceral pain used by international societies have changed over the years. These differences have a great impact on the way researchers study chronic pelvic/visceral pain. Recently, the role of systemic changes, including the role of the central nervous system, in the perpetuation and chronification of pelvic/visceral pain has gained weight. Consequently, researchers are using animal models that resemble those systemic changes rather than using models that are organ- or tissue-specific. In this review, we discuss the advantages and disadvantages of using bladder-centric and systemic models, enumerating some of the central nervous system changes and pain-related behaviors occurring in each model. We also present some drawbacks when using animal models and pain-related behavior tests and raise questions about possible, yet to be demonstrated, investigator-related bias. We also suggest new approaches to study chronic pelvic/visceral pain by refining existing animal models or using new ones.

Perineural invasion in endometriotic lesions contributes to endometriosis-associated pain

Purpose

Recent studies have shown that abnormal distribution of pelvic nerves contributes to endometriosis-associated pain. However, the relationship between neurogenesis and pain severity in endometriosis still remains uncertain, which makes it an enigma for both gynecologists as well as neuropathologists. In this study, we tried to explore a special phenomenon, perineural invasion (PNI), in deep infiltrating endometriosis (DIE) and investigated the correlation between PNI- and DIE-associated pain.

Patients and methods

The study was conducted in the Department of Obstetrics and Gynecology of the First Affiliated Hospital of Sun Yat-sen University from June 2012 to January 2015. In total, 64 patients with DIE were enrolled. They received laparoscopically surgical resection of endometriotic lesions. The Kruskal–Wallis and Mann–Whitney tests were used for comparisons of enumeration data. Spearman rank correlation was used for linear analysis.

Results

Immunohistochemical analysis demonstrated that PNI was commonly found in DIE lesions. Patients were divided into PNI (+) group and PNI (−) group. The visual analog scale scores of dysmenorrhea, dyspareunia, and chronic pelvic pain were higher in PNI (+) group than in PNI (−) group. Also, we found significantly increased density of newly formed nerve fibers as well as microvessels in lesions of PNI (+) group. Further, double immunofluorescence showed a closely spatial nerve–vessel network in the endometriotic lesion of PNI (+) group. More importantly, correlation analysis revealed positive relation between the density of newly formed nerve fibers in the lesion and the density of microvessels in lesions of PNI (+) group.

Conclusion

This study suggests that PNI in endometriotic lesions plays an important role in endometriosis-associated pain, mainly through a mechanism named “neuroangiogenesis”.