{"paper_id":"652a97a7-5a7a-48de-a2e3-14a2fc36f057","body_text":"TEST YOURSELF: ANSWER\nA 45-year-old woman with a pre-sacral mass lesion: diagnosis\nand discussion\nInderjeet Nagra & Alistair J. Stirling & Steven L. J. James\nPublished online: 26 November 2009\n# ISS 2009\nKeywords Endometriosis . Foraminal expansion . Sacrum\nDiagnosis\nEndometriosis presenting a s a pre-sacral mass lesion\ncausing sacral foraminal expansion and S1 radiculopathy.\nDiscussion\nThe MR examination demonstrates a 6×2.5-cm pre-sacral\nmass lesion that is extending into and expanding the left S1\nexit foramen. This mass extends into the epidural fat,\ndisplacing and partially surrounding the S1 nerve, but it did\nnot extend distally to affect the exiting S2 or S3 nerves. The\nlesion shows a heterogeneous signal pattern on T1- and T2-\nweighted sequences with focal areas of high signal intensity\non the T1-weighted sequences indicative of small areas of\nhaemorrhage. The lesion is predominantly hyperintense to\nmuscle on T2 weighting and following contrast medium\nadministration, and a relatively uniform enhancement\npattern is identified. Trans-sacral biopsy by an approach\nlateral to the exit foramen was performed to exclude\nrecurrent rectal carcinoma. The biopsy material demon-\nstrated endometriosis characterised by endometrial glands\nsurrounded by endometrial stroma with strong positivity for\noestrogen and progesterone. As a result, the patient was\ncommenced on hormonal treatment and the neurological\nsymptoms improved.\nAlthough endometriosis is a common condition affecting\nwomen of reproductive age, it may rarely affect both the\ncentral and peripheral nervous systems. The exact preva-\nlence is unknown, but a greater number of cases affecting\nthe peripheral nervous system have been reported, the\ncommonest being the sciatic nerve [ 1]. Presentation is\ntypically with cyclical pain in a sciatic distribution with\nsensory loss in the S1 dermatome and motor weakness.\nSymptoms may result from either direct compression or\nfibrosis of the nerve. The symptoms are usually progressive\nunless treated and prolonged compression can lead to\nirreversible damage.\nA number of theories have been postulated to explain the\nextra-uterine spread of endometriosis [ 2]. In the ovary, the\ncommonest site of endometriosis outside of the uterus,\nlymphatic drainage from the uterus has been suggested to\nbe the cause [ 3]. Distant sites of extra-pelvic endometriosis,\nsuch as the thorax or central nervous system, have been\nattributed to haematological transport, but coeloemic tissue\nmetaplasia has also been postulated, as endometriosis can\noccur in patients who have never menstruated or even in\npost-menopausal women [ 4]. This has been refuted by\nother workers who have found asymmetric sciatic nerve\nendometriosis and diaphragmatic disease more commonly\non the right side, supporting the menstrual reflux theory\nbecause of the transport of endometrial cells in the cycle of\nperitoneal fluid redistribution [ 5]. In the pelvis, the left\nThe case presentation can be found at doi:10.1007/s00256-009-0831-6\nI. Nagra : S. L. J. James ( *)\nDepartment of Radiology,\nThe Royal Orthopaedic Hospital NHS Foundation Trust,\nBirmingham B31 2AP , UK\ne-mail: steven.james@roh.nhs.uk\nA. J. Stirling\nDepartment of Spinal Surgery,\nThe Royal Orthopaedic Hospital NHS Foundation Trust,\nBirmingham B31 2AP , UK\nSkeletal Radiol (2010) 39:199 –200\nDOI 10.1007/s00256-009-0832-5\n\nsciatic and lumbosacral plexus is protected by interposition\nof the sigmoid colon and in the right hypochondrium, the\nfalciform ligament acts as a site for implantation [ 5]. In this\ncase, it seems likely that the lesion originated in the pre-sacral\nspace and extended into the epidural fat, subsequently\nexpanding the S1 foramen.\nThe inherent soft tissue contrast of MR imaging makes\nthis the method of choice for evaluating endometriosis\n[1, 6]. Lesions are typically of high signal intensity on\nT1- and T2-weighted sequences with a surrounding low\nintensity rim due to the presence of a fibrous capsule [ 1, 6].\nFat-suppressed and STIR sequences make endometriotic\nlesions more conspicuous. The areas of central high signal\nintensity on T1-weighted sequences are caused by blood\ndegradation products of different ages and the paramagnetic\neffects of methaemoglobin. V ariable signal intensity was\nseen in our case because of the quantity and age of the\nhaemorrhage and the proportion of endometrial cells and\nstroma. Endometriotic lesions do not usually enhance,\nalthough mild enhancement can occur, as was identified\nin this case.\nThe differential diagnosis for mass lesions causing\nneural foraminal widening and nerve root symptoms is\nwide and includes both benign and malignant conditions\n(see Table 1).\nThe commonest differential diagnosis is a peripheral nerve\nsheath tumour (PNST), which can be divided into benign\n(neurofibroma or schwannoma) and malignant categories.\nThey are soft tissue tumours arising from the spinal nerve root\nand may have a dumbbell shape on MR imaging. They are\nslow-growing and plexiform neurofibromas can involve a\nlong segment of nerve. They are usually of low signal\nintensity on T1- and of high signal intensity on T2-weighted\nsequences [7]. The signal characteristics may be difficult to\ndistinguish from endometriosis as lesions can appear\nheterogeneous if internal degeneration or necrosis is present,\nas is commonly identified in schwannomas. Malignant\nPNSTs grow more rapidly, show central necrosis and have\nan ill-defined border [ 7]. Other benign differentials to be\nconsidered are tuberculosis, more commonly occurring in the\ncervical or thoracic spine. Uncommonly, hydatid cysts present\nwith a lesion affecting a vertebral body as a result of a\nportovertebral shunt. They tend to be multicystic, cause bone\ndestruction, but typically preserve the disc space and do not\ninvolve the spinal cord [ 8]. Chordomas are rare, aggressive\nmalignant tumours arising from ectopic notochord remnants,\nespecially in the sacro-coccygeal or spheno-occipital-clival\nregions. On MR imaging, they display low to intermediate\nsignal intensity on T1- and very high signal intensity on\nT2-weighted sequences. Chordomas enhance heterogeneously\nand cause local bony destruction. Haemorrhagic necrosis can\nalso occur within the tumour leading to areas of high signal on\nT1 [9].\nEarly diagnosis of endometriosis is important as prolonged\ncompression and fibrosis of nerves can lead to irreversible\ndamage. Treatment options depend on whether fertility is to be\npreserved, as preferential treatment would then be directed\ntowards pharmacological suppression of ovarian hormones\nrather than surgical resection of the endometriotic lesions. In\nselected patients in whom medical therapy has failed,\nexcisional surgery to decompress the nerve can be considered.\nIn older patients or in resistant cases, a hysterectomy and\noophorectomy can be considered combined with hormonal\ntherapy.\nReferences\n1. Y ekeler E, Kumbasar B, Tunaci A, Barman A, Bengisu E, et al.\nCyclical sciatica caused by infiltrative endometriosis: MRI find-\nings. Skeletal Radiol. 2004;33:165 –8.\n2. Mannan K, Altaf F, Maniar S, Tirabosco R, Sinisi M, Carlstedt T.\nCyclical sciatica: endometriosis of the sciatic nerve. J Bone Jt Surg\nBr. 2008;90(1):98–101.\n3. Ueki M. Histologic study of endometriosis and examination of\nlymphatic drainage in and from the uterus. Am J Obstet Gynecol.\n1991;165(1):201–9.\n4. Suginami H. A reappraisal of the coelomic metaplasia theory by\nreviewing endometriosis occurring in unusual sites and instances.\nAm J Obstet Gynecol. 1991;165:214 –18.\n5. V ercellini P , Abbiati A, Viganò P , Somigliana ED, Daguati R,\nMeroni F, et al. Asymmetry in distribution of diaphragmatic\nendometriotic lesions: evidence in favour of the menstrual reflux\ntheory. Hum Reprod. 2007;22:2359 –67.\n6. Moeser P , Donofrio PD, Karstaedt N, Bechtold R, Greiss FC Jr. MRI\nfindings of sciatic endometriosis. Clin Imaging. 1990;14:64–6.\n7. Lin J, Martel W. Cross-sectional imaging of peripheral nerve sheath\ntumours: characteristics on CT, MR and US. Am J Roentgenol.\n2001;176:75–82.\n8. Zibis AH, Markonis A, Karantanas AH. Unusual causes of spinal\nforaminal widening. Eur Radiol. 2000;10:144 –8.\n9. Kivrak AS, Koc O, Emlik D, Kiresi D, Odev K, Kalkan E.\nDifferential diagnosis of dumbbell lesions associated with spinal\nneural foraminal widening: imaging features. Eur J Radiol.\n2009;71:29–41.\nBenign conditions Malignant conditions\nBenign peripheral nerve sheath tumour Malignant peripheral nerve sheath tumour\nTarlov cyst Metastases/lymphoma\nSpinal hydatid disease Chordoma\nTuberculous or pyogenic spondylitis Solitary plasmacytoma\nTable 1 Benign and malignant\nconditions causing spinal\nforaminal widening\n200 Skeletal Radiol (2010) 39:199 –200","source_license":"CC0","license_restricted":false}