{"paper_id":"cc85453e-8bd9-4b3b-a539-c0ca1794a5fb","body_text":"Neurosurg Focus  Volume 39 • September 2015\nneurosurgical  \n focus Neurosurg Focus 39 (3):E15, 2015\nE\nndom Etriosis  (EM) is a common gynecological dis-\nease that affects the endometrial glands and stroma \noutside the uterine cavity, mainly in the peritoneum, \novaries, and rectovaginal septum. It affects nearly 5%–\n10% of women in their reproductive years (ages 15–49 \nyears), and its annual incidence is 0.1%.\n6,48 EM commonly \npresents with pelvic pain but can produce sciatic, obtura-\ntor, or femoral nerve symptoms. Although the first histo-\nlogically proven case was described in 1955 by Denton \nand Sherrill\n17 and more than a hundred of such cases have \nsince been reported, the mechanism of nerve involvement \nwith EM remains enigmatic. We present 2 cases of EM \nwith sciatic neuropathy. We hypothesize that involvement \nof the lumbosacral plexus (LSP) in selected cases can be \nexplained by perineural spread of EM from the uterus to \nthe LSP along the pelvic autonomic nerves. We prove that \nour theory is applicable to other cases by testing this theo-\nry in a case reported in the literature.\nPart I: Institutional Case Reports\nCase 1\nPresentation\nA 49-year-old woman was referred to our institution in \nJune 2013 with a diagnosis of lumbosacral plexopathy of \nunknown etiology. Her relevant medical history was sig -\nnificant for a ureteral stricture and cervical and lumbar \nspine degenerative disease. She had no history of EM.\nHistory\nHer symptoms started in October 2011 after she lifted a \nheavy object. She developed low-back pain radiating to the \nleft buttock. Over subsequent months she gradually devel-\noped left lower-extremity weakness and numbness.\nMRI of the lumbar spine done in May 2012 failed to re-\nveal any significant abnormalities. MRI of the pelvis (Fig. \n1) performed in October 2012 demonstrated an amorphous \nAbbRevIA tIoNs DIE = deep infiltrating endometriosis; EM = endometriosis; IHP = inferior hypogastric plexus; LSP = lumbosacral plexus.\nsubmItted April 29, 2015.  ACCePted June 16, 2015.\nINClude wheN CItINg DOI: 10.3171/2015.6.FOCUS15208.\n* Drs. Siquara de Sousa and Capek contributed equally to this work.\nMagnetic resonance imaging evidence for perineural \nspread of endometriosis to the lumbosacral plexus: report \nof 2 cases\n*Ana C. siquara de sousa, md ,1,4 stepan Capek, md,1,5 benjamin m. howe, md,2  \nmark e . Jentoft, md,3 Kimberly K. Amrami, md ,2 and Robert J. s pinner, md1\nDepartments of 1Neurosurgery, 2Radiology, and 3Anatomic Pathology, Mayo Clinic, Rochester, Minnesota; 4Department of \nAnatomic Pathology, Gaffrée e Guinle University Hospital, Rio de Janeiro, Brazil; and 5International Clinical Research Center,  \nSt. Anne’s University Hospital Brno, Czech Republic\nSciatic nerve endometriosis (EM) is a rare presentation of retroperitoneal EM. The authors present 2 cases of catame -\nnial sciatica diagnosed as sciatic nerve EM. They propose that both cases can be explained by perineural spread of EM \nfrom the uterus to the sacral plexus along the pelvic autonomic nerves and then further distally to the sciatic nerve or \nproximally to the spinal nerves. This explanation is supported by MRI evidence in both cases. As a proof of concept, the \nauthors retrieved and analyzed the original MRI studies of a case reported in the literature and found a similar pattern \nof spread. They believe that the imaging evidence of their institutional cases together with the outside case is a very \ncompelling indication for perineural spread as a mechanism of EM of the nerve.\nhttp://thejns.org/doi/abs/10.3171/2015.6.FOCUS15208\nKey w o Rds endometriosis; sciatic nerve; sciatica; magnetic resonance imaging; autonomic pathways\n1©AANS,  2015\nUnauthenticated | Downloaded 06/11/26 03:40 AM UTC\n\n\nA. C. siquara de sousa et al.\nenhancing soft-tissue mass, thought to represent scar tis -\nsue or other granulation tissue, at the sciatic notch associ-\nated with the L-5 and S-1 spinal nerves. The mass extend-\ned along the L4–S1 spinal nerves proximally. The nerve \nthemselves were hyperintense on T2-weighted images and \nenhancing on postcontrast scans. The gluteal musculature \nshowed signs of acute and chronic denervation. PET/CT \nstudies from October 2012 demonstrated an area of in -\ncreased uptake at the sciatic notch compared with the sur-\nrounding normal musculature (Fig. 1B).\nExamination\nOn neurological examination the patient had a left foot \ndrop with markedly reduced strength in the left anterior \ntibialis (Grade 1/5), toe extensor (Grade 1/5), and peronei \nmuscles (Grade 0/5). Her sensory examination showed re-\nduction to pin and light touch over the left lateral calf and \nmedial foot, with a qualitative sensation alteration to pin \nin the lateral foot and posterior thigh.\nElectromyography conducted in June 2013 revealed \na left lumbosacral plexopathy affecting the L-5 and S-1 \nmyotomes associated with active denervation.\nMRI of the LSP performed at the same time (Fig. 2), \nwith and without intravenous contrast material, showed \nan ill-defined and slightly spiculated soft-tissue mass as -\nsociated with the sciatic nerve at the sciatic notch. The \nmass itself was heterogeneous on T1- and T2-weighted \nsequences with cystic areas. Post-Gd scans demonstrated \nlinear abnormality extending from the body of the uterus \nto the LSP or sciatic nerve proximal to the sciatic notch. \nThe nerve itself appeared to be enlarged and infiltrated \nby the mass. A lesion with similar characteristics was dis-\ncovered in the left obturator internus muscle. The gluteal \nmusculature and obturator internus muscle exhibited signs \nof chronic denervation.\nProcedure\nA fine-needle aspiration biopsy of the lesion (Fig. 2F) \nwas performed and revealed epithelial tissue with scant \nstroma positive for estrogen receptors (glands and stroma) \nand CD10 (stroma) (Fig. 3). The diagnosis of EM was es-\ntablished.\nPostoperative Course\nThe patient was started on hormonal therapy. On fol -\nlow-up 6 months later the patient reported resolution in \npelvic pain and improved cyclic gluteal pain.\nCase 2\nPresentation\nA 32-year-old woman with no relevant medical history \npresented to our institution in November 2000 with cata-\nmenial low-back, hip, and right lower-extremity pain ac-\ncompanied by tingling in the distal leg.\nHistory\nInitially, in the fall of 1998 the patient noticed mild hip \nand pelvic pain, and numbness and tingling in the right \nlower extremity associated with her menstrual cycles. \nThese symptoms progressively worsened.\nMRI of the pelvis from February 2000 showed in -\ncreased T2 signal along the right lateral pelvic wall in -\nvolving the obturator internus and piriformis muscles. \nChanges were noted to be consistent with an inflamma -\ntory process and EM was suspected; however, a discern -\nible endometrioma was not identified.\nIn March 2000 the patient underwent laparoscopy, \nwhich revealed peritoneal EM. She was started on gonad-\notropin-releasing hormone agonist treatment and experi -\nenced complete resolution of the pain. This therapy was \ndiscontinued after 4 months due to side effects, and the \nsymptoms returned.\nExamination\nElectromyography done in November 2000 confirmed \nright sciatic neuropathy proximal to the innervation of the \nmedial hamstrings. The abnormalities in the lumbar para-\nspinal muscles suggested involvement of the LSP .\nMRI of the pelvis performed in November 2000 (Fig. \n4) demonstrated a massively enlarged right sciatic nerve \nat the sciatic notch, which was hyperintense on T1- and \nT2-weighted sequences and heterogeneously enhancing \non post-Gd scans. A similar heterogeneous abnormality \nwith hemosiderin depositions was noted to be in the right \npiriformis and obturator internus muscles and in the right \nFIg. 1. Case 1. 2012 MRI and PET/CT studies. A T1-weighted axial im -\nage (A) demonstrates an enlarged left sciatic nerve associated with a \nspiculated soft-tissue mass with hyperintense areas suggestive of intra -\nlesional bleeding (arrowhead) . A composite axial FDG PET/CT image \n(b) shows increased uptake compared with surrounding musculature in \nthe area corresponding to the left sciatic nerve (arrowhead) . A coronal \noblique T2-weighted fat-saturated image (C)  demonstrates a hyperin -\ntense left S-1 spinal nerve with an area of abnormality (dashed arrow)  \nextending along the nerve from a heterogeneous spiculated mass (ar -\nrowhead) proximally through the S-1 sacral foramen. A coronal oblique \nT2-weighted fat-saturated image ( d) shows similarly increased signal in \nthe left L-4 (dotted arrow) and L-5 (dashed arrow) spinal nerves proximal \nto the soft-tissue mass (arrowhead) .\nNeurosurg Focus  Volume 39 • September 20152\nUnauthenticated | Downloaded 06/11/26 03:40 AM UTC\n\n\nPerineural spread of endometriosis\nischium. Based on the signal characteristics, these lesions \nwere concluded to be foci of EM.\nTreatment\nEM was confirmed as the etiology based on the positive \nresponse to the gonadotropin-releasing hormone agonist, \nwhich the patient was started on in 2001. On follow-up 5 \nyears later, the patient reported mild residual pelvic pain, \nno radiating pain, and improved ability to walk longer dis-\ntances. MRI performed in 2005 demonstrated near-com -\nplete resolution of EM (Fig. 4D).\nPart II: Retrospective Reinterpretation of a \nPreviously Published Case\nWe wondered if our theory would apply to other cas -\nes in the literature. As a proof of concept, we retrieved \na case reported by colleagues (Domínguez-Páez et al. 18) \nof a patient with right sciatic nerve EM. We reviewed the \nmost recent MR images (2014) and MR images obtained \n3 years earlier (2011). On the MRI from 2011 the sciatic \nnerve was massively enlarged and surrounded by hetero-\ngeneous tissue with focal hemorrhages suggestive of EM. \nAs in our case we could follow the abnormality extending \nfrom the cervix to the right LSP , which also had similar \nimaging characteristics (Fig. 5A and B). On the 2014 MRI \nthe sciatic nerve decreased in size, although it was still en-\nlarged compared with its normal size as well as the L4–S1 \nspinal nerves. The spinal nerves (Fig. 5C and D) appeared \nidentical to those in our Case 1 (Fig. 1C and D). We be -\nlieve this case indeed represents another example of peri-\nneural spread of EM and further strengthens our theory.\ndiscussion\nWe propose that perineural spread from the organ to \nthe LSP , demonstrated in pelvic cancer1,11,22 including cer-\nvical cancer,25 applies to EM as well and represents an \nalternate mechanism in selected cases. The possibility of \nEM tracking along the nerves as a form of spread was de-\nscribed by Possover et al.;37 however, such an anatomical, \nmechanistic explanation as the one described in the pres-\nent report has not yet been postulated. We provide compel-\nling evidence by presenting our 2 cases and the previously \npublished case18 that showed signs of perineural spread.\nWe hypothesize that endometrial glands and stroma in-\nfiltrate the uterine plexus, part of the inferior hypogastric \nplexus (IHP). From the IHP , EM continues to grow toward \nthe sacral plexus along the sacral and pelvic splanchnic \nnerves and toward the lumbar plexus along the hypogastric \nnerves (Fig. 6). Within the plexus, EM can spread proxi-\nmally to the spinal nerves (Figs. 1C and D and 5C and D) \nor distally to the arborizing nerves. We were surprised by \nthe presence of EM in the pelvic muscles (Figs. 2D and E \nand 4A and B) and pelvic bone (Fig. 4A and B) in a pat -\ntern similar to that which has been described for perineu-\nFIg. 2. Case 1. 2013 MRI. An axial spoiled gradient recall (SPGR) Gd-enhanced image (A) demonstrates an area of enhancing \nabnormality (dashed arrow) extending from the body of the uterus to the left LSP and left sciatic nerve, which is markedly enlarged \nand appears to be infiltrated by the abnormality (arrowhead) . The gluteal musculature is atrophic (asterisks) . A coronal oblique \nT2-weighted image (b) shows increased signal of the L-4 and L-5 spinal nerves (arrowheads)  proximal to an area of spiculated hy -\nperintense soft-tissue mass (arrow) . Increased signal on a T2-weighted image (C) is also demonstrated by the left S-1 spinal nerve \n(arrowhead). A coronal oblique SPGR image ( d) demonstrates enhancing lesion with center area of decreased signal in the upper \nportion of the left obturator internus muscle (arrowhead)  and an abnormally enhancing and heterogeneous left uterosacral liga -\nment, possibly representing extension of endometrial tissue from the cervix to the inferior hypogastric plexus (dashed arrow) . The \nsame lesions were hyperintense on a T2-weighted coronal image ( e: arrowhead and dashed arrow), the central area presumably \nrepresenting hemosiderin collection. A CT-navigated biopsy (F)  of the soft-tissue mass in close vicinity of the LSP was performed \nand revealed endometriosis.\nNeurosurg Focus  Volume 39 • September 2015 3\nUnauthenticated | Downloaded 06/11/26 03:40 AM UTC\n\n\nA. C. siquara de sousa et al.\nral spread of malignant cancer to muscle 8 and bone.9 We \ntheorize that these deposits could result from perineural \nspread of EM along the motor and bone branches from \nt h e  L SP.\nHow EM invades the uterine plexus is not clear. Up to \n90% of women with EM\n6 have adenomyosis, and deep ad-\nenomyotic nodules have been demonstrated to be closely \nassociated with nerves.\n5 We theorize that endometriotic \ncells and stroma can propagate from deep adenomyotic \nnodules along the fine uterine nerves toward the IHP in \nthe uterosacral ligament (Fig. 2D and E) and then as de -\nscribed above. The perineural spread as a possible expla-\nnation is supported by reciprocal interactions between EM \nand nerves.\n5,6,12,37 Not only does EM promote neurogen -\nesis,5 but in turn the nerves promote angiogenesis and EM \ngrowth.6,39 EM can be classified into several subtypes, of \nwhich deep infiltrating endometriosis (DIE) seems to be \nthe most aggressive and most challenging to treat due to \nits invasive nature.\n5 DIE is more painful than other forms \nof EM, which can be explained by its propensity to invade \nand extend along the pelvic nerves.\n2–4 DIE can cause ure-\nteral or rectosigmoid strictures and sacral plexus entrap -\nment requiring demanding reconstructive surgeries. 3,48 \nIntraneural invasion of major somatic nerves such as the \nsciatic or obturator nerve prevents complete resection. \nDIE can also be more challenging to diagnose as it may \nhave no peritoneal manifestation at all\n36 or may present \nonly with peritoneal “pockets,”6 probably caused by sub-\nperitoneal scarring and retraction.\nPossover et al.37 were the first to propose a “neural hy-\npothesis,” describing a major role of the pelvic nervous \nsystem in EM. To support the theory, they correlated \ncommon locations of DIE with major components of the \npelvic sympathetic system. Although the parasympathetic \nsystem might be implicated as well,\n27 other authors have \nobserved a similar distribution of DIE.14,15,52\nEM is heterogeneously hyperintense on T1-weighted \nMRI due to blood collections and hypointense from hemo-\nsiderin depositions. On T2-weighted MRI, it has a similar \nheterogeneous appearance. Typical, but very nonspecific, \nis retraction of surrounding tissue due to scarring. The \nperineural spread can be visualized as an abnormality ex-\ntending from the uterus toward the LSP (Figs. 2A and 5A \nand B), which is hyperintense on T2-weighted MRI and \navidly enhancing on post-Gd scans. The LSP and branch-\ning nerves infiltrated with EM are enlarged, hyperintense \nFIg. 3. Case 1. Pathology.  A: A single benign-appearing gland is present with minimal underlying stroma. H & E, original magnifi -\ncation ×200.  b: The gland and scant underlying stroma are positive for estrogen receptors. Estrogen receptor immunohistochem -\nistry, original magnification × 200.  C: The stroma is also positive for CD10. Original magnification × 200. These staining patterns in \nconjunction with the morphology support the diagnosis of endometriosis.\nNeurosurg Focus  Volume 39 • September 20154\nUnauthenticated | Downloaded 06/11/26 03:40 AM UTC\n\n\nPerineural spread of endometriosis\non T2-weighted MR images, and heterogeneously enhanc-\ning on contrast-enhanced images.\nWe understand that intraperitoneal seeding with sub -\nsequent nerve compression is the most probable explana-\ntion for most cases with neural symptoms. A review of the \nliterature revealed several other cases of interest. These \ncan be divided into 2 subgroups: 1) cases with nerve in -\nvolvement and no peritoneal disease; and 2) cases with in-\ntraneural (e.g., intrasciatic) EM with either unspecified or \nsome peritoneal disease. Possover and Chiantera\n36 report-\ned 3 cases of sciatic nerve EM, one of which was intraneu-\nral. None of these cases had any peritoneal disease. Pham \net al.35 reported a case in a patient presenting with sciatic \nnerve weakness. At the time of presentation, the patient \nhad no peritoneal disease, and on biopsy EM was found in \nthe epineurium. Interestingly, gluteal and pelvic muscles \ndemonstrated denervation, pointing to a more widespread \nprocess. Torkelson et al.\n46 reported 2 cases, one of which \nhad no peritoneal disease and intraneural EM of the sci -\natic nerve. Ceccaroni et al.13 reported another case of sci-\natic nerve EM and no peritoneal disease. Several authors, \nhowever, reported cases of intraneural sciatic nerve EM, \nwhich could be explained by perineural spread.\n24,30,31,43,56 \nWaer et al.51 reported a case of EM with perineural spread \nalong the obturator nerve. We wonder if cases of EM with \nnerve and bone or muscle involvement could be explained \nby perineural spread along the periosteal and muscle \nbranches. Redwine and Sharpe\n40 reported a case of obtu -\nrator nerve EM extending to the ilium. A case of sciatic \nnerve EM that spread to the femur was described by Oei et \nal.33 Also, the second case of sciatic nerve EM reported by \nTorkelson et al.46 had EM in the ischial tuberosity in a pat-\ntern that was reminiscent of that described in perineural \nspread of cancer and in Case 2.\n9 In their series, Possover \nand Chiantera36 reported a case of sciatic nerve EM with \nextension to the obturator internus muscle—again, a simi-\nlar pattern to that seen in our case and to that described \nin perineural cancer spread.8 We further hypothesize that \ncases of conus medullaris EM could be explained as an \nextension of the same process intradurally along the sacral \nand lumbar nerve roots, 20,44 possibly with subsequent in-\ntradural seeding 19 as proposed in perineural spread of \nprostate cancer.10\nlimitations\nWe understand that our article has several limitations. \nIt is based on 2 individual cases, and further research is \nneeded to confirm perineural spread of EM as an alter -\nnative explanation for sciatic nerve EM. We acknowledge \nthat the theory of retrograde menstruation with intraperi-\ntoneal seeding first proposed by Sampson7,41 is the likely \nexplanation for most cases of sacral plexus EM. We pro-\nFIg. 4. Case 2. MRI. An axial T2-weighted MR image (A) demonstrates \nheterogeneously increased signal in the enlarged right sciatic nerve (el -\nlipse). The obturator internus muscle is infiltrated with a heterogeneous \nhyperintense soft-tissue mass with hemosiderin depositions (thin arrow) . \nThe muscle itself and the piriformis muscle (arrowheads)  show diffusely \nincreased signal suggestive of denervation. Another nodulus of similar \ncharacteristics is observed in the right ischium (thick arrow) . The same \nstructures demonstrate prominent heterogeneous enhancement on \naxial T1-weighted Gd-enhanced MR imaging ( b) (thin arrow: obturator \ninternus muscle; thick arrow : ischium; arrowheads: piriformis muscle; \nellipse: sciatic nerve). An axial T2-weighted image (C)  demonstrates a \nmassively enlarged and infiltrated right sciatic nerve at the sciatic notch \n(arrowhead). An axial follow-up T1-weighted image ( d) obtained 6 years \nlater shows marked improvement of the sciatic nerve enlargement (ar -\nrowhead).\nFIg. 5. Outside case. MRI. An axial T1-weighted Gd-enhanced image \n(A) demonstrates an enhancing abnormality extending from the cervix \n(asterisk) to the sciatic notch and the sciatic nerve (dashed arrow) . A \ncoronal T2-weighted fat-saturated image ( b) demonstrates the same \nhyperintense and heterogeneous abnormality (dashed arrow)  extending \nfrom the cervix (asterisk) . Coronal fat-saturated fast spin echo images \n(C and d) from an MRI examination performed 3 years later show the \nhyperintense and enlarged right S-1 and L-4 spinal nerves demonstrat -\ning signs of perineural spread (C, dashed  arrow, the S-1 spinal nerve; D, \ndashed arrow, the L-4 spinal nerve).\nNeurosurg Focus  Volume 39 • September 2015 5\nUnauthenticated | Downloaded 06/11/26 03:40 AM UTC\n\n\nA. C. siquara de sousa et al.\nvide a secondary explanation applicable to selected cas -\nes supported by compelling evidence based on imaging \nstudies and review of the literature. Vercellini et al. 47 re-\nviewed the reported cases of sciatic nerve EM published \nuntil 2002 and found that the right sciatic nerve was sig -\nnificantly more involved than the left sciatic nerve. They \nproposed that this could be explained anatomically as the \nsigmoid “protects” the left sacral plexus. However, when \nwe used the same methodology, reviewed all cases they \nreferenced, and added all cases published until the time of \nwriting (47 new cases),\n13,16,21,23,26,28,29,31,32,34,35,38,42,43,45,49,50,53–55 \nwe could not confirm their finding—there was no statisti-\ncally significant difference between the left and right side. \nWe acknowledge other possible explanations such as lym-\nphatic or hematogenous spread, but none of these theories \nwould explain a continuous band of EM extending from \nthe uterus to the LSP as seen in the imaging evidence pre-\nsented here. Separated, individual lesions (e.g., EM focus \nin lungs) would be expected with hematogenous or lym -\nphogenous spread. None of our patients had evidence sug-\ngestive of such lesions; in addition, this has been excluded \nin our Case 1 by whole-body PET/CT scanning.\nConclusions\nWe described the cases of 2 patients with sciatic nerve \nEM. We demonstrated that our theory is applicable to oth-\ner cases reported in the literature. We theorize that both \ncan be explained by perineural spread of EM from the \nuterus to the sacral plexus along the visceral autonomic \nnerves. From the plexus, EM can spread proximally to the \nspinal nerves or distally to the sciatic nerve or pelvic bone \nand musculature using bone and muscle nerve branches. \nSuch a complete, mechanistic explanation for selected cas-\nes of EM presenting with nerve symptoms has not, to our \nknowledge, been presented until now.\nAcknowledgments\nWe are very thankful for the contribution of Dr. Caterina \nGiannini, who initially evaluated the specimen in Case 1. We \nare very grateful to Drs. Domínguez-Páez and Socolovsky, who \nprovided us with imaging material of the case they previously \nreported on.\nDr. Capek is supported by European Regional Development \nFund–Project FNUSA-ICRC (CZ.1.05/1.1.00/02.0123).\nReferences\n 1. Aghion DM, Capek S, Howe BM, Hepel JT, Sambandam S, \nOyelese AA, et al: Perineural tumor spread of bladder cancer \ncausing lumbosacral plexopathy: an anatomic explanation. \nActa Neurochir (Wien) 156:2331–2336, 2014 [Erratum in \nActa Neurochir (Wien) 157:153, 2015]\n 2. Anaf V , El Nakadi I, De Moor V , Chapron C, Pistofidis G, \nNoel JC: Increased nerve density in deep infiltrating endome -\ntriotic nodules. Gynecol Obstet Invest 71:112–117, 2011\n 3. Anaf V , El Nakadi I, Simon P, Van de Stadt J, Fayt I, Simon-\nart T, et al: Preferential infiltration of large bowel endome-\nFIg. 6. Illustration of perineural spread of endometriosis. An artistic rendition of perineural spread of endometriosis along the \npelvic autonomic nerves to the sacral plexus and further distally to the sciatic nerve or proximally to the spinal nerves. A possible \nintradural extension along the nerve roots is depicted. Used with permission of the Mayo Foundation for Medical Education and \nResearch. All rights reserved.\nNeurosurg Focus  Volume 39 • September 20156\nUnauthenticated | Downloaded 06/11/26 03:40 AM UTC\n\n\nPerineural spread of endometriosis\ntriosis along the nerves of the colon. Hum Reprod 19:996–\n1002, 2004\n 4. Anaf V , Simon P, El Nakadi I, Fayt I, Buxant F, Simonart T, \net al: Relationship between endometriotic foci and nerves in \nrectovaginal endometriotic nodules. Hum Reprod 15:1744–\n1750, 2000\n 5. Anaf V , Simon P, El Nakadi I, Fayt I, Simonart T, Buxant F, \net al: Hyperalgesia, nerve infiltration and nerve growth factor \nexpression in deep adenomyotic nodules, peritoneal and ovar-\nian endometriosis. Hum Reprod 17:1895–1900, 2002\n 6. Asante A, Taylor RN: Endometriosis: the role of neuroangio-\ngenesis. Annu Rev Physiol 73:163–182, 2011\n 7. Burney RO, Giudice LC: Pathogenesis and pathophysiology \nof endometriosis. Fertil Steril 98:511–519, 2012\n 8. Capek S, Amrami KK, Howe BM, Spinner RJ: Perineural \ntumor spread to the muscle: An alternative for muscle metas-\ntasis? Clin Anat 28:560–562, 2015 (Letter) \n 9. Capek S, Howe BM, Froemming AT, Amrami KK, Spin-\nner RJ: Perineural spread in pelvic malignancies can be an \nalternate explanation for pelvic bony metastases rather than \nhematogenous spread. A report of two cases. Skeletal Radiol \n44:1365–1370, 2015\n10. Capek S, Howe BM, Tracy JA, García JJ, Amrami KK, Spin-\nner RJ: Prostate cancer with perineural spread and dural ex -\ntension causing bilateral lumbosacral plexopathy: case report. \nJ Neurosurg 122:778–783, 2015\n11. Capek S, Sullivan PS, Howe BM, Smyrk TC, Amrami KK, \nSpinner RJ, et al: Recurrent rectal cancer causing lumbosa -\ncral plexopathy with perineural spread to the spinal nerves \nand the sciatic nerve: an anatomic explanation. Clin Anat \n28:136–143, 2015\n12. Carvalho L, Podgaec S, Bellodi-Privato M, Falcone T, Abrão \nMS: Role of eutopic endometrium in pelvic endometriosis. J \nMinim Invasive Gynecol 18:419 – 427, 2011\n13. Ceccaroni M, Clarizia R, Cosma S, Pesci A, Pontrelli G, \nMinelli L: Cyclic sciatica in a patient with deep monolateral \nendometriosis infiltrating the right sciatic nerve. J Spinal \nDisord Tech 24:474–478, 2011\n14. Chapron C, Fauconnier A, Vieira M, Barakat H, Dousset B, \nPansini V , et al: Anatomical distribution of deeply infiltrat-\ning endometriosis: surgical implications and proposition for a \nclassification. Hum Reprod 18:157–161, 2003\n15. Chapron C, Santulli P, de Ziegler D, Noel JC, Anaf V , Streuli \nI, et al: Ovarian endometrioma: severe pelvic pain is associ -\nated with deeply infiltrating endometriosis. Hum Reprod \n27:702–711, 2012\n16. Chauvin C, Azria E, Mahieu-Caputo D, Madelenat P: [Endo -\nmetriosis of the ischio-rectal excavation at the contact of the \nsciatic nerve: a case report of neurolysis by pararectal inci -\nsion.] Gynecol Obstet Fertil 38:142–146, 2010 (Fr)\n17. Denton RO, Sherrill JD: Sciatic syndrome due to endometrio -\nsis of sciatic nerve. South Med J 48:1027–1031, 1955\n18. Domínguez-Páez M, de Miguel-Pueyo LS, Medina-Imbroda \nJM, González-García L, Moreno-Ramírez V , Martín-Gallego \nA, et al: [Sciatica secondary to extrapelvic endometriosis \naffecting the piriformis muscle. Case report.] Neurocirugia \n(Astur) 23:170–174, 2012 (Span)\n19. Duke R, Fawcett P, Booth J: Recurrent subarachnoid hemor-\nrhage due to endometriosis. Neurology 45:1000–1002, 1995\n20. Erbayraktar S, Acar B, Saygili U, Kargi A, Acar U: Manage-\nment of intramedullary endometriosis of the conus medul -\nlaris. A case report. J Reprod Med 47:955–958, 2002\n21. Floyd JR II, Keeler ER, Euscher ED, McCutcheon IE: Cyclic \nsciatica from extrapelvic endometriosis affecting the sciatic \nnerve. J Neurosurg Spine 14:281–289, 2011\n22. Hébert-Blouin MN, Amrami KK, Myers RP, Hanna AS, \nSpinner RJ: Adenocarcinoma of the prostate involving the \nlumbosacral plexus: MRI evidence to support direct perineu-\nral spread. Acta Neurochir (Wien) 152:1567–1576, 2010\n23. Hettler A, Böhm J, Pretzsch M, von Salis-Soglio G: [Extra-\ngenital endometriosis leading to piriformis syndrome.] Ner -\nvenarzt 77:474–477, 2006 (Ger)\n24. Hibbard J, Schreiber JR: Footdrop due to sciatic nerve endo -\nmetriosis. Am J Obstet Gynecol 149:800–801, 1984\n25. Howe BM, Amrami KK, Nathan MA, Garcia JJ, Spinner \nRJ: Perineural spread of cervical cancer to the sciatic nerve. \nSkeletal Radiol 42:1627–1631, 2013\n26. Hughes MS, Burd TA, Allen WC: Post-traumatic catamenial \nsciatica. Orthopedics 31:400, 2008\n27. Kelm Junior AR, Lancellotti CL, Donadio N, Auge AP, Lima \nSM, Aoki T, et al: Nerve fibers in uterosacral ligaments of \nwomen with deep infiltrating endometriosis. J Reprod Im-\nmunol 79:93–99, 2008\n28. Koga K, Osuga Y, Harada M, Hirota Y, Yamada H, Akahane \nM, et al: Sciatic endometriosis diagnosed by computerized \ntomography-guided biopsy and CD10 immunohistochemical \nstaining. Fertil Steril 84:1508, 2005\n29. Lacroix-Triki M, Beyris L, Martel P, Marques B: Low-grade \nendometrial stromal sarcoma arising from sciatic nerve endo -\nmetriosis. Obstet Gynecol 104:1147–1149, 2004\n30. Lemos N, Kamergorodsky G, Ploger C, Castro R, Schor E, \nGirão M: Sacral nerve infiltrative endometriosis presenting \nas perimenstrual right-sided sciatica and bladder atonia: case \nreport and description of surgical technique. J Minim Inva -\nsive Gynecol 19:396–400, 2012\n31. Mannan K, Altaf F, Maniar S, Tirabosco R, Sinisi M, Carlst-\nedt T: Cyclical sciatica: endometriosis of the sciatic nerve. J \nBone Joint Surg Br 90:98–101, 2008\n32. Motamedi M, Mousavinia F, Naser Moghadasi A, Talebpoor \nM, Hajimirzabeigi A: Endometriosis of the lumbosacral plex-\nus: report of a case with foot drop and chronic pelvic pain. \nActa Neurol Belg [epub ahead of print], 2015\n33. Oei SG, Peters AA, Welvaart K, Bode PJ, Fleuren GJ: Ag-\ngressive endometriosis in bone. Lancet 339:1477–1478, 1992\n34. Papapietro N, Gulino G, Zobel BB, Di Martino A, Denaro \nV: Cyclic sciatica related to an extrapelvic endometriosis of \nthe sciatic nerve: new concepts in surgical therapy. J Spinal \nDisord Tech 15:436–439, 2002\n35. Pham M, Sommer C, Wessig C, Monoranu CM, Pérez J, Stoll \nG, et al: Magnetic resonance neurography for the diagnosis \nof extrapelvic sciatic endometriosis. Fertil Steril 94:351.\ne11–351.e14, 2010\n36. Possover M, Chiantera V: Isolated infiltrative endometriosis \nof the sciatic nerve: a report of three patients. Fertil Steril  \n87:417.e17–417.e19, 2007\n37. Possover M, Rhiem K, Chiantera V: The “neurologic hypoth-\nesis”: a new concept in the pathogenesis of the endometrio-\nsis? Gynecol Surg 2:107–111, 2005\n38. Possover M, Schneider T, Henle KP: Laparoscopic therapy \nfor endometriosis and vascular entrapment of sacral plexus. \nFertil Steril 95:756–758, 2011\n39. Possover M, Tersiev P, Angelov DN: Comparative study of \nthe neuropeptide-Y sympathetic nerves in endometriotic \ninvolved and noninvolved sacrouterine ligaments in women \nwith pelvic endometriosis. J Minim Invasive Gynecol \n16:340–343, 2009\n40. Redwine DB, Sharpe DR: Endometriosis of the obturator \nnerve. A case report. J Reprod Med 35:434–435, 1990\n41. Sampson JA: Peritoneal endometriosis due to menstrual dis -\nsemination of endometrial tissue into the peritoneal cavity. \nAm J Obstet Gynecol 14:442– 469, 1927\n42. Shetty A, Fishwick KT, Rambani R, Acharya S: An unusual \ncase of post-traumatic endometriosis involving the sciatic \nnerve in the right greater sciatic notch. J Obstet Gynaecol \n30:642, 2010\n43. Soriano Guillén AP, Mayayo Sinués E, Mir Torres A, Lanzón \nLaga A: Endometriosis ciática: una causa poco conocida de \nciatalgia. Rehabilitación 48:64 – 67, 2014\nNeurosurg Focus  Volume 39 • September 2015 7\nUnauthenticated | Downloaded 06/11/26 03:40 AM UTC\n\n\nA. C. siquara de sousa et al.\n44. Steinberg JA, Gonda DD, Muller K, Ciacci JD: Endometrio-\nsis of the conus medullaris causing cyclic radiculopathy. J \nNeurosurg Spine 21:799–804, 2014\n45. Teixeira AB, Martins WA, d’ Ávila R, Stochero L, Alberton \nL, Bezerra S, et al: Endometriosis of the sciatic nerve. Arq \nNeuropsiquiatr 69:995–996, 2011\n46. Torkelson SJ, Lee RA, Hildahl DB: Endometriosis of the sci-\natic nerve: a report of two cases and a review of the literature. \nObstet Gynecol 71:473–477, 1988\n47. Vercellini P, Chapron C, Fedele L, Frontino G, Zaina B, Cro-\nsignani PG: Evidence for asymmetric distribution of sciatic \nnerve endometriosis. Obstet Gynecol 102:383–387, 2003\n48. Vercellini P, Viganò P, Somigliana E, Fedele L: Endome-\ntriosis: pathogenesis and treatment. Nat Rev Endocrinol \n10:261–275, 2014\n49. Volpi E, Seinera P, Ferrero A, Dompè D: Laparoscopic neu-\nrolysis of the pelvic sciatic nerve in a case of catamenial foot-\ndrop. J Minim Invasive Gynecol 12:525–527, 2005\n50. Wadhwa V , Thakkar RS, Maragakis N, Höke A, Sumner CJ, \nLloyd TE, et al: Sciatic nerve tumor and tumor-like lesions—\nuncommon pathologies. Skeletal Radiol 41:763–774, 2012\n51. Waer P, Samson I, Sinnaeve F, Sciot R, Pans S: Perineural \nspread of endometriosis along the obturator nerve into the ad-\nductor thigh compartment. Jpn J Radiol 30: 446–449, 2012\n52. Witz CA: Current concepts in the pathogenesis of endome -\ntriosis. Clin Obstet Gynecol 42:566–585, 1999\n53. Yao S, Liang Y, Jiang H: Cyclic sciatica due to endometriosis \nof the sciatica nerve: neurolysis with combined laparoscopic \nand transgluteal approaches. J Minim Invasive Gynecol \n21:S133, 2014\n54. Yekeler E, Kumbasar B, Tunaci A, Barman A, Bengisu E, \nYavuz E, et al: Cyclic sciatica caused by infiltrative endome-\ntriosis: MRI findings. Skeletal Radiol 33:165–168, 2004\n55. Yoshimoto M, Kawaguchi S, Takebayashi T, Isogai S, Kurata \nY, Nonaka S, et al: Diagnostic features of sciatica without \nlumbar nerve root compression. J Spinal Disord Tech \n22:328–333, 2009\n56. Zager EL, Pfeifer SM, Brown MJ, Torosian MH, Hackney \nDB: Catamenial mononeuropathy and radiculopathy: a treat -\nable neuropathic disorder. J Neurosurg 88:827–830, 1998\ndisclosure\nThe authors report no conflict of interest concerning the materi -\nals or methods used in this study or the findings specified in this \npaper.\nAuthor Contributions \nConception and design: all authors. Acquisition of data: all \nauthors. Analysis and interpretation of data: all authors. Drafting \nthe article: all authors. Critically revising the article: all authors. \nReviewed submitted version of manuscript: all authors. Approved \nthe final version of the manuscript on behalf of all authors: \nSpinner. Administrative/technical/material support: Capek, Howe, \nJentoft. Study supervision: Spinner, Siquara de Sousa, Amrami.\nCorrespondence\nRobert J. Spinner, Mayo Clinic, Gonda 8-214, 200 First St. SW, \nRochester, MN 55905. email: spinner.robert@mayo.edu.\nNeurosurg Focus  Volume 39 • September 20158\nUnauthenticated | Downloaded 06/11/26 03:40 AM UTC","source_license":"CC0","license_restricted":false}