Skeletal Radiol (2004) 33:165–168 DOI 10.1007/s00256-003-0663-8
Ensar Yekeler Basak Kumbasar Atadan Tunaci Ahmet Barman Ergin Bengisu Ekrem Yavuz Mehtap Tunaci
Received: 17 March 2003 Revised: 5 May 2003 Accepted: 6 May 2003 Published online: 23 January 2004 ISS 2004 E. Yekeler ()) · B. Kumbasar · A. Tunaci · A. Barman · M. Tunaci Department of Radiology, Istanbul Faculty of Medicine, Istanbul University, 34390 Capa, Istanbul, Turkey e-mail:
[email protected] Tel.: +90-212-5337505 Fax: +90-212-6310728 E. Bengisu Department of Obstetrics and Gynecology, Istanbul Faculty of Medicine, Istanbul University, 34390 Capa. Istanbul, Turkey E. Yavuz Department of Pathology, Istanbul Faculty of Medicine, Istanbul University, 34390 Capa, Istanbul, Turkey
CASE REPORT
Cyclic sciatica caused by infiltrative endometriosis: MRI findings
Abstract Endometriosis, an important gynecological disorder of reproductive women, affects most commonly the ovaries and less frequently the gastrointestinal tract, chest, urinary tract, and soft tissues. Endometriosis classically appears on MRI as a mass with a large cystic component and variable signal intensities on T1- and T2-weighted images due to the presence of variable degradation of hemorrhagic products. Endometriosis in an atypical location, an infiltrative appearance and without cystic-hemorrhagic components has rarely been described. We report on a 33-year-old woman with cyclic sciatica due to histologically documented infiltrative endometriosis involving the area of the left sciatic notch.
Introduction Endometriosis, which is the result of functional endometrium located outside the uterus, is an important gynecological disorder primarily affecting women during their reproductive years [1]. It has been detected in 4.5–32% of women undergoing laparoscopic evaluation for chronic pelvic pain and in 4.5–33% of women with infertility [2]. It is estimated that 30–50% of women with endometriosis are infertile, and 20% of infertile women have endometriosis [1]. The ovaries are the most common site affected with the gastrointestinal tract, chest, urinary tact, and soft tissues less commonly involved [3]. Symptoms associated with endometriosis include infertility and pelvic pain.
Keywords Endometriosis · Sciatica · Magnetic resonance imaging
Common symptoms include dysmenorrhea, dyspareunia, cyclical back pain, and rectal discomfort [1]. We report on the case of an endometrioma located in the left sciatic notch, involving the left piriformis, gemellus and obturator internus muscles, which presented as cyclic sciatica.
Case report A 33-year-old infertile woman was referred for episodic pain in her left leg associated with difficulty in walking. The clinical history revealed cyclic left-sided sciatica of more than 2 years’ duration. Attacks of stabbing and shooting pain began on the first day of the menstruation and lasted for 3 or 4 days. The symptoms recurred during the following cycle after a pain-free interval. She could not
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Fig. 1 An infiltrative soft tissue mass (arrows) located in the left sciatic notch is seen on non-contrast T1-weighted (A) and T2weighted spin-echo images (B), isointense and slightly hyperintense to the unaffected muscles, respectively. Contrast-enhanced T1-weighted spin-echo image (C) reveals mild contrast enhancement of the lesion. In all sequences, the affected muscles adjacent
to the mass show slightly higher signal intensity than the mass. Axial fat-suppressed contrast-enhanced T1-weighted spin-echo image (D) shows bone marrow involvement (arrow), and the coronal image (E) demonstrates well the infiltrative mass (hollow arrows), muscle (thin arrows), and ischial bone marrow (thick arrow) involvements
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Discussion
Fig. 2 Histological examination of the mass reveals the focus of endometriosis externa containing endometrioid glands and endometrioid stroma with hemosiderin-laden macrophages (hematoxylin–eosin, original magnification125)
walk or extend her knee during the painful periods. With time, the symptoms gradually worsened leaving her with progressively shorter pain-free intervals, until she experienced constant pain, more severe during walking. Neurological examination, nerve conduction studies, and electromyography were performed to localize the patient’s symptoms. It was concluded that the results were compatible with partial axon-loss lesions of left postganglionic L5 and S1 nerve roots with possible involvement of the lumbosacral plexus branches destined for the sciatic nerve. Magnetic resonance imaging (MRI) of the lumbar spine performed a year earlier was reported to be normal. Sciatica was suspected, and pelvic MRI examination was performed on a 1 T MRI system (Magnetom Impact; Siemens, Erlangen, Germany). MRI examination revealed an infiltrative soft tissue mass of irregular contour located in the course of the left sciatic nerve behind the ischium which measured 55x3 cm in size. The mass was isointense and slightly hyperintense to the muscle on T1- and T2-weighted spin-echo images, respectively, and exhibited mild heterogeneous contrast enhancement after gadolinium administration. The gluteus minimus, piriformis, superior and inferior gamellus, and obturatus internus were also affected and showed slightly higher signal intensity than the mass on T1- and T2weighted spin-echo images (Fig. 1A–C). Contrast-enhanced fatsuppressed T1-weighted spin-echo images also depicted contrast ehancement within the medullary portion of the ischium without any cortical destruction (Fig. 1D). Coronal plane images also depicted well the muscular and bone marrow involvement (Fig. 1E). Because of the history of cyclical pain and infertility, the lesion was considered an endometrioma. Consequently, an ultrasound-guided biopsy of the lesion was performed. Histological examination revealed areas of typical endometrial glands surrounded by stroma and bordered by vessels with occasional foci of hemosiderin-laden macrophages, typical of endometriosis (Fig. 2). Since the patient wished to preserve her reproductive functions, she was placed on a regimen of hormonal suppression therapy. She received goserelin acetate, LH-RH-Analoge (3.6 mg per 28 days, subcutaneous implant), for 6 months. After the therapy, control MRI examination revealed no marked changes in appearance of the mass but she then succeeded in becoming pregnant and her symptoms gradually improved.
Endometriosis is classically defined as the presence of functional endometrial glands and stroma outside the uterine cavity. In the older literature, endometriosis was further classified as endometriosis interna and endometriosis externa. Endometriosis interna referred to endometrial tissue within the uterine musculature whereas endometriosis externa referred to endometrial tissue in all other sites [1]. Although generally confined to intrapelvic sites, such as ovaries, pelvic wall, or peritoneum, endometrial cells have been reported in the pleura, skin, lung, and skeletal muscles of the extremities [4, 5]. Various causative mechanisms have been proposed for sciatic nerve endometriosis. It has been suggested that the genital endometriosis nodules or endometrial cells of the retrograde menstruation migrate to the sciatic nerve via a peritoneal diverticulum. During surgery, uterine vascular damage can result in sciatic nerve endometriosis via the hematological route, especially in patients with no other sites of endometriosis [6]. Although it is a rare cause of sciatica, endometriosis should be considered if the pain has a cyclical nature. A full clinical, neurological, and radiological evaluation is mandatory to rule out lumbar disk disease, spondylotic nerve root compression, hip-joint arthritis, primary neural tumor, metastasis, and gluteal artery aneurysm [7]. Early recognition of endometriosis compressing the sciatic nerve is important to prevent irreversible damage to the sciatic nerve and, if diagnosed early, surgery with local excision and/or hormonal therapy with GnRH agonists or oral contraceptives can be curative [8, 9]. Since the appearance of the first case report on sciatic nerve endometriosis, published by Schlicke in 1946 [10], 56 additional cases causing cyclic sciatica have been reported [7, 11, 12, 13]. In the majority of the published cases, the diagnosis has been made by histological examination or typical clinical symptoms [7, 12]. However, a few cases have been detected by imaging modalities such as computed tomography (CT) and MRI [6, 11, 14]. Fedele et al. [7] described “phantom endometriosis” as causing sciatica in three cases. Although imaging modalities failed to confirm the diagnosis, hormonal therapy was successful in eradicating the symptoms in these cases. In the histological evaluation of laparoscopically obtained material from 25 patients with cyclic sciatica, Vilos et al. [12] detected five endometriosis nodules, 19 peritoneal pockets and/or peritoneal endometriosis, and one inflammatory peritoneum. They hypothesized that the pain associated with these lesions is more likely referred pain originating from the pelvic peritoneum than irritation of the lumbosacral plexus of the sciatic nerve. In different pelvic locations, CT and MRI findings of endometriosis can vary from solid or complex cystic masses to cystic lesions with thick or thin walls [6, 14,
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15]. With MRI, endometriomas often exhibit relatively high signal intensity on T1-weighted images and mixed high and low signal intensity on T2-weighted images, reflecting the degenerated blood products [1,14]. However, the MRI signal intensity is quite variable depending on the quantity and the age of the hemorrhage, and the proportion of endometrial cells and stroma within the lesion [6,14]. In our case, the lesion was isointense and slightly hyperintenserelative to muscle on T1- and T2weighted images, respectively, because of its stromal component (Fig. 1A–C). The adjacent muscles and bone marrow demonstrated a diffuse increase in the signal intensity on T2-weighted images and diffuse contrast
enhancement due to probable inflammation and edema (Fig. 1B,D,E). An interesting feature of our case is the atypical location and the infiltrative characteristic of the lesion, which induced sciatic pain by compression of the nerve at the sciatic notch. Because the lesion had no marked increase in signal intensity on T2-weighted and contrastenhanced T1-weighted images, a fibrotic tumor infiltrating the surrounding muscles could be considered in the differential diagnosis. However, the cyclic rhythm of the pain and the history of infertility in our patient suggested a diagnosis of endometriosis.
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