Laparoscopic morphological aspects and tentative explanation of the aetiopathogenesis of isolated endometriosis of the sciatic nerve: a review based on 267 patients

Abstract

Background: Endometriosis of the sciatic nerve (ESN) is considered a rare disease. How can endometriosis develop within the sciatic nerve; a structure which has nothing in common with the uterus either anatomically or functionally, and why it occurs in the absence of any retroperitoneal/parametric endometriosis, is unknown. A better understanding of the pathophysiology of this enigmatic disease may improve its diagnosis and therapy. Materials and Methods: From a pool of 452 patients operated for ESN, only patients with “isolated” endometriosis of the sciatic nerve” confirmed at laparoscopy were included in this study. Patients with suspicion of ESN by extension from a parametric, ovarian or other intraperitoneal deeply infiltrating endometriosis were excluded from this study. Main outcome measure: All information acquired during the preoperative patient’s medical history and clinical examination were collected and compared with the morphological aspects of the disease observed by the laparoscopic treatment. Patients were classified into three groups according to the time interval between the onset of sciatic pain and the time of surgery: less than 1 year (Group 1), between 1 and 3 years (Group 2), and more than 3 years (Group 3). Results: Two hundred sixty-seven consecutive patients were included in this study. In Group 1 (n=67), 76% of the patients presented with cyclical sciatica, without sensory or motor disorders of the lower limbs. Laparoscopic exploration found in the great majority of these patients only the presence of an isolated endometrioma in the nerve itself, the size of which was proportional to the time elapsed since the onset of pain. In Group 2 (n=83), pain had become constant in 91% of the patients with neurological disorders of the lower limb (foot drop, Trendelenburg gait, atrophied muscles) in about 30% of patients. Laparoscopic examination revealed, in addition to intraneural cystic lesions, a retroperitoneal fibrosis in more than 80% of the patients. In the third group (N=117), more than 80% of the patients presented with neurological disorders of the lower limb, with, on laparoscopic examination, massive retroperitoneal fibrosis with endometriomas in the nerve and adjacent pelvic wall muscles in all patients and an infiltration of the obturator nerve in 41% of patients. Conclusions: The different morphologic aspects of ESN do not correspond to different forms of the disease, but obviously to one single disease at different stages of its evolution. ENS starts first with the development of an endometrioma within the sciatic nerve, then develops in a second step a perineural fibrosis that expands into the whole retroperitoneal space and finally involves surrounding anatomical structures. The ESN is a very particular pathology because it induces a completely new aspect on the pathogenesis of endometriosis: all hypothesis of implanted endometrial cells following retrograde menstruation, angiogenic spread, lymphogenic spread or the metaplasia theory cannot explain the pathogenesis of this disease. ESN obviously does not develop from “genital metastatic cells”. A possible hypothesis for explanation the pathogenesis of ESN, could consist in the development of endometriosis of the nerve from progenitor stem cells present within the nerve, pluripotent cells which, for an as yet unknown reason (possibly in connection with iterative inflammations and micro-damages of the nerve itself), mutate and proliferate to form endometriosis.

Isolated Deep Infiltrating Endometriosis of the Sciatic Nerve: A Case Report and Overview of the Literature

“…Consistent with our case and the mass localization, patients more commonly exhibit leg motor weakness and sciatic dermatome hypoesthesia [24]. Interestingly, Possover noted that less than 20% of isolated sciatic endometriosis cases within the first year of experiencing pain are accompanied by neurologic disorders such as foot drop, Trendelenburg gait, sacral hypoesthesia, and gluteal atrophy [8]. Other symptoms that usually occur are related to abdominal-pelvic organ involvement: dysmenorrhea, chronic pelvic pain, right iliac fossa pain, dysuria, dyspareunia, and infertility [25].…”

“…Eventually, cysts filled with dark hemorrhagic content (noted as "chocolate cysts" in the literature) are formed and are usually seen during the laparoscopic exploration of the unknown origin of sciatica [11]. These cysts grow with each menstrual bleeding, causing constant pressure and nerve damage, finally resulting in worsening cyclical sciatica or even constant pain with significant menstrual exacerbations [8].…”

“…Lesions that predominantly affect the sciatic nerve without infiltrating surrounding muscle or neurovascular structures are presented as cyclical sciatica in over 75% of cases, less frequently as constant sciatica [8]. They experience worsening sciatic pain that usually begins in the gluteal area and radiates down the posterolateral side of the leg and heel [22].…”

“…Although DIE solely affecting the nerves without any observable endometriosis within the pelvic cavity is considered to be rather uncommon, Possover et al documented isolated endometriosis of the sciatic nerve in 27 patients over a five-year period [7]. Possover's [8] 17-year-long follow-up study showed 267 cases of endometriotic lesions with no additional manifestations within the peritoneal cavity and no DIE of the parametrium. Endometriotic lesions impacted solely the sciatic nerve in approximately 67 cases, with no influence on any other pelvic tissue, such as surrounding muscles (4 cases per year, on average).…”

Manejo laparoscópico y farmacológico del dolor de miembro pélvico en pacientes con endometriosis profunda: resultados de una serie de casos

“…1,7 El dolor cíclico del nervio ciático también es sugerente de endometriosis, éste fue documentado por primera vez en 1955 8 y es especialmente problemático cuando dificulta la marcha y se asocia a pie caído, el cual suele aparecer pasados dos años de iniciados los síntomas, a diferencia del dolor que mejora por las noches, el cual se asocia a un atrapamiento vascular del nervio. 9,10 El dolor crónico es patológico en sí mismo y suele persistir, aunque el estímulo o la herida ya no esté presente, es resultado de arreglos funcionales y estructurales en el sistema nervioso central que mantienen la percepción del dolor y facilitan su expansión a otras regiones. 4 El dolor es perpetuado por una sensibilización central y aparece dolor miofascial secundario a la activación de puntos de dolor, este mecanismo explica por qué el dolor continúa a pesar de que la paciente haya recibido terapia médica, quirúrgica o ambas.…”