{"paper_id":"95c0e686-444c-4d21-87d3-a4774eecc45c","body_text":"Review began\n 05/01/2026 \nReview ended\n 05/07/2026 \nPublished\n 05/09/2026\n© Copyright \n2026\nSamadov et al. This is an open access\narticle distributed under the terms of the\nCreative Commons Attribution License CC-\nBY 4.0., which permits unrestricted use,\ndistribution, and reproduction in any\nmedium, provided the original author and\nsource are credited.\nDOI:\n 10.7759/cureus.108539\nLeft-Sided Sciatic Nerve Endometriosis Presenting\nAs Chronic Thigh Pain and Muscle Atrophy: A\nCase Report\nParviz Samadov \n, \nKamil Aliyev \n, \nIlhama Eldarova \n, \nAkbar Hajiyev \n, \nEmil Hasanov \n1.\n Radiology, Liv Bona Dea Hospital, Baku, AZE \n2.\n Gynecology, Liv Bona Dea Hospital, Baku, AZE \n3.\n Pathology, Liv\nBona Dea Hospital, Baku, AZE\nCorresponding author: \nKamil Aliyev, \nkamilelmira99@gmail.com\nAbstract\nSciatic nerve endometriosis is a rare and often underdiagnosed form of deep infiltrating endometriosis\ninvolving the lumbosacral plexus or sciatic nerve. We present the case of a 40-year-old woman with chronic\nleft thigh and pelvic pain exacerbated during menstruation, accompanied by limited mobility. Pelvic MRI\nrevealed a lesion along the left sciatic nerve with characteristic hemorrhagic and inflammatory features, as\nwell as muscle atrophy indicative of chronic denervation. Combined surgical and gynecologic intervention\nconfirmed the diagnosis and resulted in significant symptom improvement. This case highlights the\nimportance of clinical suspicion and MRI in early diagnosis to prevent irreversible neurologic damage.\nCategories:\n Obstetrics/Gynecology, Radiology, Pathology\nKeywords:\n catamenial sciatica, chronic thigh \npain, deep infiltrating endometriosis, gemelli muscles, muscle atrophy,\nneuropathic pain, obturator internus muscle, pelvic mri, sciatic nerve endometriosis\nIntroduction\nEndometriosis is a prevalent gynecological disorder characterized by the presence of functional endometrial\ntissue outside the uterine cavity, primarily affecting pelvic organs, such as the ovaries, fallopian tubes, and\nperitoneum \n[1]\n. Although the condition commonly manifests with symptoms, including dysmenorrhea,\nchronic pelvic pain, and infertility, involvement of extrapelvic structures remains rare and diagnostically\nchallenging \n[2]\n. Among these atypical presentations, sciatic nerve endometriosis represents a particularly\nuncommon and underrecognized form of deep infiltrating endometriosis, in which ectopic endometrial\nimplants infiltrate or compress the lumbosacral plexus or sciatic nerve \n[3,4]\n.\nThe clinical presentation of sciatic nerve endometriosis is often nonspecific and may mimic other\nneuropathic or musculoskeletal disorders, leading to frequent misdiagnosis and delayed treatment \n[5]\n.\nPatients typically report catamenial sciatica, characterized by cyclical neuropathic pain along the sciatic\nnerve distribution, accompanied by motor deficits and progressive muscle atrophy if left untreated \n[6,7]\n. The\npathophysiological mechanisms underlying neural involvement are incompletely understood, and\nhypotheses include retrograde menstruation with peritoneal implantation, lymphovascular dissemination,\ndirect extension from adjacent pelvic endometriotic lesions, and perineural invasion \n[8]\n.\nMRI has emerged as the imaging modality of choice for the detection of sciatic nerve endometriosis \n[9]\n. MRI\nfindings typically include T1 hyperintense foci corresponding to blood products and T2 hypointense rims\nreflecting hemosiderin deposition or fibrosis, along with nerve thickening and surrounding inflammatory\nchanges \n[10]\n. Early radiologic recognition is critical to guide timely surgical intervention and prevent\nirreversible neurologic impairment \n[11]\n.\nThis report presents a rare case of left-sided sciatic nerve endometriosis, which is less common than right-\nsided involvement, given the predominance of right-sided involvement reported in the literature \n[9]\n. This\ncase underscores the importance of maintaining a clinical suspicion in women presenting with catamenial\nsciatic pain and highlights the pivotal role of MRI in the diagnosis and treatment planning for optimal\npatient outcomes.\nCase Presentation\nWe present the case of a 40-year-old woman with a two-year history of left thigh and pelvic pain, which had\nprogressively worsened over the past seven months. The patient also experienced limited mobility and\nreported increased pain during menstruation. Previous physiotherapy interventions had exacerbated her\nsymptoms. Lumbar disc pathology and nerve root involvement were considered, and an MRI of the pelvis\nwas recommended.\nMRI findings\n1\n1\n2\n3\n1\n \nOpen Access Case Report\nHow to cite this article\nSamadov P, Aliyev K, Eldarova I, et al. (May 09, 2026) Left-Sided Sciatic Nerve Endometriosis Presenting As Chronic Thigh Pain and Muscle\nAtrophy: A Case Report. Cureus 18(5): e108539. \nDOI 10.7759/cureus.108539\n\nMagnetic resonance imaging was performed on a Siemens 3.0-Tesla Magnetom Skyra system (Siemens\nHealthineers, Erlangen, Germany). The protocol included axial T1- and T2-weighted sequences; fat-\nsuppressed T1-weighted and fat-suppressed T2-weighted sequences; and coronal and axial short-tau\ninversion recovery (STIR) imaging. Axial diffusion-weighted imaging (DWI) with corresponding apparent\ndiffusion coefficient (ADC) maps was also obtained with coverage focused on the pelvic region.\nPelvic MRI revealed a mass-like lesion along the left sciatic nerve at the level of the greater sciatic foramen.\nThe lesion exhibited a T2 hypointense rim and central heterogeneous T1 hyperintense hemorrhagic\ncomponents, extending into the piriformis, obturator internus, and superior gemellus muscles\n(Figures \n1A\n-\n1B\n).\nFIGURE\n 1: Left sciatic nerve lesion on T1 fat-suppressed MRI at six-\nmonth follow-up.\n(A) Initial T1 fat-suppressed image demonstrates a heterogeneous hyperintense lesion involving the left sciatic\nnerve, extending into the piriformis, obturator internus, and superior gemellus muscles (white circle). (B) Follow-up\nT1 fat-suppressed image at 6 months shows an increase in lesion size (white circle).\nThe sciatic nerve was observed to be thickened and edematous, consistent with inflammation. MRI results\nfurther identified atrophy in the left gluteus maximus, superior and inferior gemellus, quadratus femoris,\npiriformis, and internal obturator muscles. Additionally, a T2/STIR hyperintense signal was noted, which\nmay indicate denervation edema or inflammatory changes. Follow-up images after six months demonstrated\ndisease progression and increasing muscle atrophy (Figures \n2A\n-\n2B\n). \nFIGURE\n 2: Coronal T2-weighted images of the left sciatic nerve lesion at\nsix-month follow-up.\n(A) Initial coronal T2 image demonstrates the lesion (white circle), with a hypointense rim consistent with\nhemosiderin deposition. The sciatic nerve shows thickening along its course (red arrows). (B) Follow-up T2 image\nat six months shows lesion progression (white circle) and thickening along the sciatic nerve (red arrows).\nAxial DWI and ADC map demonstrated no evidence of restricted diffusion within the lesion (Figures \n3A\n-\n3B\n).\nThe patient underwent combined surgical resection and gynecologic intervention.\n \n2026 Samadov et al. Cureus 18(5): e108539. DOI 10.7759/cureus.108539\n2\n of \n5\n\nFIGURE\n 3: Diffusion imaging of the left sciatic nerve lesion.\n(A) Diffusion-weighted imaging (DWI) shows the lesion (white circle) without significant diffusion restriction. (B)\nThe corresponding apparent diffusion coefficient (ADC) map confirms the absence of restricted diffusion.\nHistopathological examination revealed fibroadipose and skeletal muscle tissue infiltrated by foci of\nendometriosis. The lesions were composed of endometrial-type glands and surrounding endometrial stroma\nembedded within the soft tissue, skeletal muscle fibers, and around nerve bundles. The glands were variably\nsized and lined by a single layer of cuboidal to columnar epithelium, without cytologic atypia. The\nsurrounding endometrial-type stroma was composed of compact spindle cells resembling proliferative\nendometrial stroma. There was an associated chronic inflammatory infiltrate, scattered hemosiderin-laden\nmacrophages, and areas of hemorrhage. Foci of fibrosis and reactive changes within adjacent skeletal muscle\nfibers were present, including mild fiber atrophy and separation by fibrous tissue. No cytologic atypia,\ncomplex glandular architecture, or features of malignancy were identified (Figures \n4A\n-\n4B\n). Postoperative\nfollow-up demonstrated significant symptom improvement and no residual lesions on MRI.\nFIGURE\n 4: Histopathologic findings of endometriosis in deep soft\ntissue.\n(A) Low-power photomicrograph of H&E showing a dilated endometrial-type gland (black asterisk) lined by a\nsingle layer of cuboidal to columnar epithelium (blue arrows) and surrounded by compact endometrial-type\nstroma (yellow arrow) within the fibrocollagenous soft tissue (black arrow). (B) Low-power photomicrograph of\nH&E showing additional foci of endometrial-type glands (blue arrows) and stroma (yellow arrow) infiltrating\nfibroadipose tissue and skeletal muscle and extending around nerve bundles, accompanied by chronic\ninflammation, hemosiderin deposition, and fibrosis. No cytologic atypia or malignant features were observed.\nScale bars = 200 \nμ\nm.\nDiscussion\nSciatic nerve endometriosis represents a rare form of deep infiltrating endometriosis, characterized by the\npresence of ectopic endometrial tissue affecting the lumbosacral plexus or sciatic nerve. Although\nendometriosis predominantly affects pelvic organs, extrapelvic neural involvement is infrequent and often\nunderdiagnosed due to nonspecific symptoms and delayed imaging assessments \n[1,2]\n.\nPatients typically exhibit catamenial sciatica, progressive neuropathic pain, and motor impairment.\nConsistent with previously documented cases, our patient experienced chronic pelvic and thigh pain, with\nexacerbation during menstruation, which serves as a critical clinical indicator for diagnosis \n[3,4]\n. Muscle\natrophy and movement limitations have also been reported in cases with extended nerve involvement \n[5]\n. In\nour patient, atrophy of the obturator internus, gemelli, quadratus femoris, and gluteus maximus muscles,\nalong with associated STIR hyperintensity, was indicative of chronic neurogenic denervation. Given the\nlesion's location at the greater sciatic foramen, these findings likely reflect involvement or compression of\nadjacent sacral plexus branches, including the nerve to obturator internus, the nerve to quadratus femoris,\n \n2026 Samadov et al. Cureus 18(5): e108539. DOI 10.7759/cureus.108539\n3\n of \n5\n\nand the inferior gluteal nerve. Ipsilateral piriformis atrophy with STIR hyperintensity further supports\ndenervation associated with deep infiltrating endometriosis at the sciatic notch region, including the nerve\nto piriformis (S1-S2).\nNumerous studies indicate a predominance of right-sided sciatic nerve endometriosis \n[6]\n, potentially\nattributable to pelvic anatomical structures and the patterns of peritoneal fluid circulation. One hypothesis\nsuggests that the rectosigmoid colon, located in the left pelvis, may offer partial protection to left-sided\nextrapelvic structures, thereby reducing the likelihood of implantation on that side \n[9]\n. Contrarily, our\npatient exhibited left-sided sciatic involvement, a less frequently documented occurrence, thus contributing\nto the limited body of literature on left-sided cases.\nA significant aspect of our case was the patient's history of physiotherapy, which exacerbated the pain. In\nthe absence of gynecological correlation, sciatic endometriosis may initially be misdiagnosed as lumbar disc\npathology or musculoskeletal disease, resulting in delayed diagnosis and inappropriate treatment \n[4,7]\n. In\nour patient, the catamenial pattern of pain and careful correlation with MRI signal characteristics facilitated\nearly radiologic suspicion of endometriosis prior to surgical confirmation. MRI is currently the preferred\nimaging modality for assessing pelvic nerve involvement in endometriosis. Typical MRI features include T1\nhyperintense foci due to blood products and T2 hypointense components corresponding to hemosiderin\ndeposition or fibrotic tissue \n[3,8]\n. In our case, the lesion exhibited a T2 hypointense rim with a central\nheterogeneous signal and T1 hyperintense components, findings consistent with hemorrhagic content.\nAsymmetric thickening of the sciatic nerve and obliteration of the surrounding fat planes further supported\nneural infiltration. Serial imaging demonstrated lesion progression and increasing muscle atrophy,\nunderscoring the importance of follow-up imaging in symptomatic patients.\nThe pathogenesis of sciatic nerve endometriosis remains a subject of debate. Proposed mechanisms include\nretrograde menstruation with peritoneal implantation, coelomic metaplasia, lymphovascular spread, and\ndirect extension from adjacent pelvic endometriotic foci \n[5,11]\n. Additionally, neural spread along perineural\nplanes has been described in magnetic resonance neurography studies \n[8,11]\n. Despite these theories, the\nprecise mechanism underlying isolated neural involvement remains unclear.\nSurgical excision is generally regarded as the primary treatment, particularly in cases presenting with\nprogressive neurologic deficits \n[1,11]\n. Hormonal therapy, including gonadotropin-releasing hormone\nanalogs, has demonstrated variable success, especially in perimenopausal women; however, it may not\nreverse established neural damage \n[7]\n. In our patient, a combination of surgical resection and gynecologic\nintervention resulted in significant postoperative pain reduction, with no evidence of residual lesions on\nfollow-up MRI.\nConclusions\nSciatic nerve endometriosis should be considered a potential diagnosis in women presenting with chronic\nthigh or pelvic pain, catamenial sciatica, and muscle atrophy. MRI is the preferred modality for early\ndetection and facilitates timely surgical intervention. The occurrence of left-sided involvement is\nuncommon, highlighting the necessity for comprehensive imaging evaluation and clinical correlation to\nprevent misdiagnosis.\nAdditional Information\nAuthor Contributions\nAll authors have reviewed the final version to be published and agreed to be accountable for all aspects of the\nwork.\nConcept and design:\n  \nKamil Aliyev, Parviz Samadov, Emil Hasanov, Ilhama Eldarova, Akbar Hajiyev\nAcquisition, analysis, or interpretation of data:\n  \nKamil Aliyev, Parviz Samadov, Emil Hasanov, Ilhama\nEldarova, Akbar Hajiyev\nDrafting of the manuscript:\n  \nKamil Aliyev, Parviz Samadov, Ilhama Eldarova, Akbar Hajiyev\nCritical review of the manuscript for important intellectual content:\n  \nKamil Aliyev, Emil Hasanov\nSupervision:\n  \nParviz Samadov\nDisclosures\nHuman subjects:\n Informed consent for treatment and open access publication was obtained or waived by all\nparticipants in this study. \nConflicts of interest:\n In compliance with the ICMJE uniform disclosure form, all\nauthors declare the following: \nPayment/services info:\n All authors have declared that no financial support\nwas received from any organization for the submitted work. \nFinancial relationships:\n All authors have\n \n2026 Samadov et al. Cureus 18(5): e108539. DOI 10.7759/cureus.108539\n4\n of \n5\n\ndeclared that they have no financial relationships at present or within the previous three years with any\norganizations that might have an interest in the submitted work. \nOther relationships:\n All authors have\ndeclared that there are no other relationships or activities that could appear to have influenced the\nsubmitted work.\nAcknowledgements\nThe authors would like to thank the radiology technologist teams for their expertise in obtaining the high-\nquality imaging necessary for the diagnosis of this case of sciatic nerve endometriosis. We also acknowledge\nthe clinical and surgical teams involved in the patient’s management and care. The authors confirm that no\nprofessional medical writing or editorial assistance was received, and no third party submitted the\nmanuscript on behalf of the authors. 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