Intramedullary Endometriosis of the Conus Medullaris

To the Editor: We read with great interest the article by Agrawal et al. () entitled, “Intramedullary Endometriosis of the Conus Medullaris: Case Report.” In particular, we wish to comment on the pathogenesis of intramedullary endometriosis of the conus medullaris in this 40-year-old woman, progressively symptomatic below the L1 level since the age of 28 years. Symptoms and signs worsened for 2 days at the onset of the menstrual cycle, ostensibly associated with periodic intraspinal bleeding. The authors describe a mass in the spinal canal involving the conus cauda region, which was densely adhesive with the conus and cauda equina and was not separable from the cord tissue and nerve roots. The mass consisted of firm, fleshy, and relatively avascular tissue, with necrosis and old hemorrhage. Figure 2A in the article represents a histological section demonstrating endometrial glands with surrounding stroma entrapped in the mesenchymal tissue. Of special significance to the discussion of pathogenesis, the uterus and genital organs were normal; specifically, there was no evidence of pelvic endometriosis found at the time of a bilateral oophorectomy subsequent to laminectomy. In 1940, Oscar Batson () described the vertebral venous network. Injecting radiopaque brilliant water color substances into the dorsal veins in the penises of male cadavers, Batson demonstrated a pattern that seemed to be an exact replica of the pattern made by the early spread of carcinoma of the prostate, with extensive filling of the vertebral veins and the bypassing of the caval veins. This specimen furnished a composite picture of the metastatic pattern of advanced cases of carcinomatosis with primary origin in the prostate. Further experiments in anesthetized monkeys confirmed these observations. In all of Batson's experiments, increased intra-abdominal pressure blocked flow into the caval venous system and facilitated flow into the vertebral venous system. His experiments indicated that, under conditions of increased abdominal pressure and during the Valsalva maneuver, blood is actually (actively) squeezed out of the intra-abdominal veins into the vertebral vein system. Batson reported that vertebral veins have many and rich communications with the veins in the spinal canal, the veins around the spinal column, and those within the bones of the column. Agrawal et al. () postulate that intraspinal endometriosis probably results from the reverse transport of endometriotic tissue via the vertebral venous system described by Batson. We cannot support the authors' position. The history, physical, and operative findings do not support that hypothesis. Not only was there no evidence of pelvic endometriosis, there was also no evidence of deeply invasive endometriosis () and no evidence of aggressive deeply infiltrating adenomyosis () from which endometriotic venous metastases might originate. The one and the only endometriotic lesion was located in the spinal cord. Endometriosis of the spinal cord is a rare lesion; it would occur much more commonly if its pathogenesis was via venous metastases from deeply invasive endometriosis or adenomyosis. In 1951, Faulconer () demonstrated varied locations of müllerian grooves, i.e., dorsolateral, lateral, ventrolateral, and ventral, on the cranial end of the genital ridge in human embryos. We postulate that the intraspinal endometriosis in this patient is a heterotopic organoid müllerian rest, developmentally misplaced embryonic müllerian tissue from müllerian grooves described by Faulconer. Of interest, a case of spinal intradural müllerianosis has been published recently (), which is not dissimilar to that of Agrawal et al., except for the presence of all three müllerian tissues: endocervicosis, endosalpingiosis, and endometriosis. We postulate that this rare case described by Agrawal et al. is a specific example of a choristoma, endometrial tissue within the spinal cord, and that a müllerian rest offers a more powerful explanatory hypothesis than venous metastases from nonexistent pelvic endometriosis. In summary, we postulate that this case of intraspinal endometriosis is truly müllerianosis (), an organoid lesion, a choristoma, a müllerian anlage misplaced during embryonic development. We further postulate that this organoid müllerian rest, in the same manner as eutopic endometrium, was subject to apoptosis as an endometrium regulator, and was not subject to apoptotic-programmed cell death (). Finally, we suggest that the intraspinal organoid lesion described by Agrawal et al. behaves more like eutopic endometrium than ectopic endometrium. In other words, we postulate that the intramedullary endometriosis of the conus medullaris described is in reality intramedullary müllerianosis of the conus medullaris. Ronald E. BattJohn YehBuffalo, New York Richard A. SmithAttleboro, Massachusetts Dan C. MartinGermantown, Tennessee Charles ChapronParis, France - 1. Agrawal A, Shetty BJ, Makannavar JH, Shetty L, Shetty J, Shetty V: Intramedullary endometriosis of the conus medullaris: Case report. Neurosurgery 59:E428, 2006. - 2. Barresi V, Cerasoli S, Vitarelli E, Donati R: Spinal intradural mullerianosis: A case report. Histol Histopathol 21:1111–1114, 2006. - 3. Batson OV: The function of the vertebral veins and their role in the spread of metastases. Ann Surg 112:138–149, 1940. - 4. Batt RE, Smith RA, Buck GM, Severino MF, Naples JD: Mullerianosis. Prog Clin Biol Res 323:413–426, 1990. - 5. Chapron C, Chopin N, Borghese B, Foulot H, Dousset B, Vacher-Lavenu MC, Vieira M, Hasan W, Bricou A: Deeply infiltrating endometriosis: Pathogenetic implications of the anatomical distribution. Hum Reprod 21:1839–1845, 2006. - 6. Faulconer RJ: Observations on the origins of müllerian groove in human embryos. Contrib Embryol 229:161–164, 1951. - 7. Goumenou AG, Matalliotakis IM, Tzardi M, Fragouli YG, Mahutte NG, Arici A: Apoptosis and differential expression of apoptosis-related proteins in endometriotic glandular and stromal cells. J Soc Gynecol Investig 11:318– 322, 2004. - 8. Leyendecker G, Herbertz M, Kunz G, Mall G: Endometriosis results from the dislocation of basal endometrium. Hum Reprod 17:2725–2736, 2002.