AUTHOR(S): Moser, Franklin G., M.D.; Tuvia, Joseph, M.D.; LaSalla, Patrick, M.D.; Llana, Josephine, M.D. Department of Radiology, Lenox Hill Hospital, (JT, FGM, LMR), Department of Neurosurgery, Roosvelt St. Lukes Medical Center (PL), and Department of Pathology, Montefiore Medical Center (JL), New York City, New York Neurosurgery 31; 962-964, 1992 ABSTRACT: EPENDYMOMAS ARE THE most common intramedullary tumor of the spinal cord. They are most common at the region of the cauda equina, accounting for up to 90% of primary tumors in that area. Extraspinal ependymomas are rare. We describe a case of an ependymoma arising in a spinal peripheral nerve root. KEY WORDS: Computed tomographic myelography; Ependymoma; Magnetic resonance imaging; Spinal neoplasms CASE REPORT A 31-year-old Hispanic woman sought treatment for lower back pain. She had been well until 3 months preceding the examination, when she developed lower back pain that radiated down the posterior aspect of her right lower extremity. The pain got progressively worse and extended to involve her left lower extremity. She denied weakness paresthesia or urinary incontinence. Her medical history was remarkable for occasional headaches, which were not severe and responded adequately to conservative treatment. The findings of physical and neurological examinations were within normal limits. There was no evidence of a spinal anomaly on plain radiographs of the spine. Magnetic resonance images of the brain revealed nothing abnormal. A T1-weighted magnetic resonance image of the spine showed an intradural mass of intermediate signal intensity dorsal to the vertebral bodies of L2 and L3 (Fig. 1). On a T2weighted image, the mass had high signal intensity, essentially isointense with the cerebrospinal fluid. The cervical and thoracic portions of the spine were normal. A myelogram showed an intradural mass below the level of the conus causing partial block (Fig. 2). A computed tomographic myelogram showed the mass extending from the L2 level to L3. The caudal segment of the mass was seen to extend laterally toward the right neural foramen of the L3 exiting root and was clearly separated from the filum terminale (Fig. 3). The patient underwent laminectomy from L1 to L4. After dural incision, a well-encapsulated, purplish
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mass was seen bulging at the L2-L3 region, displacing the nerve roots of the cauda equina. Decompression was performed, and at this point it became clear that the lesion was actually arising from within the L3 nerve root. Since the patient had no presurgical motor deficit, a decision was made not to resect the nerve root. Using microsurgery, resection of the tumor was performed. The patient tolerated the procedure well, with no complications nor any postoperative neurological deficit. Histological examination showed the mass to be typical of myxopapillary ependymoma (Fig. 4). DISCUSSION Fifty to sixty percent of spinal cord tumors of glial origin are ependymomas (3). Most commonly, these tumors involve the lower portion of the spinal cord, including the conus medullaris, filum terminale, and cauda equina, where ependymomas constitute close to 90% of the primary tumors (5). Intracranial ependymomas have their origin in the cells lining the ventricles and choroid plexus. In the spinal cord, they arise from the ependymal cells lining the central canal or its remnants and from the cells of the ventriculus terminalis in the filum terminale. Ependymomas rarely occur outside the central nervous system. These may be primary presacral tumors (4), metastasis or direct extension of a primary central nervous system tumor to adjacent tissue (6), or subcutaneous, sacrococcygeal tumors that may or may not connect to the spinal cord (2). Extradural sacral ependymomas are thought to arise from the coccygeal medullary vestige, a remnant of the primitive neural tube lined with ependymal tissue (1) . There is no known connection between this structure and the nerve roots to explain the presence of ependymal tissue in a peripheral nerve root, as in the case described here. One would have to postulate that during embryonic development, a focus of ectopic ependymal tissue was formed, and later gave rise to neoplasm. Twenty to thirty percent of ependymomas in ectopic locations are associated with spina bifida occulta, indicating developmental failure that resulted additionally in ectopic ependymal rests. In our patient, no associated anomalies were detected. Imaging of spinal ependymomas by computed tomographic myelography or by magnetic resonance imaging demonstrates an intradural, intramedullary mass, for which the prime differential diagnoses are ependymoma and astrocytoma. Signal characteristics are similar for both lesions: low on T1- and high on T2-weighted images. If the mass is large enough, it may be difficult to discern whether the lesion is intramedullary or extramedullary. This is true especially with ependymomas arising from the filum terminale or conus medullaris and extending into the extramedullary space. The differentiation of such a lesion from a meningioma or neurofibroma may be difficult, and is based on the appearance of the lesion relative to the cord, nerve roots, and filum. A preoperative diagnosis of a benign lesion such as a neurofibroma might be entertained, delaying treatment. The eccentric position of the mass relative
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Neurosurgery 1992-98 November 1992, Volume 31, Number 5 962 Ependymoma of the Spinal Nerve Root: Case Report Case Report
Received, November 18, 1991. Accepted, June 8, 1992. Reprint requests: Franklin G. Moser, M.D., Department of Imaging, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048. REFERENCES: (1-6) 1. 2.
3. 4. 5.
6.
Bale PM: Ependymal rests and subcutaneous sacrococcygeal ependymoma. Pathology 12:237- 243, 1980. Helwig EB, Stern JB: Subcutaneous sacrococcygeal myxopappilary ependymoma: A clinicopathologic study of 32 cases. Am J Clin Pathol 81:156-161, 1984. Kernohan JW, Fletcher-Kernohan EM: Ependymomas: A study of 109 cases. Assoc Res Nerv Ment Dis 16:182-209, 1935. Morantz RA, Kepes JJ, Batinsky S, Masterson BJ: Extraspinal ependymomas: Report of three cases. J Neurosurg 51:383-391, 1979. Sonnenfeld PRL, Scheithauer BW, Onofrio BM: Myxopappilary ependymoma: A clinicopathologic and immunohistochemical study of 77 cases. Cancer 56:883-893, 1985. Wolff M, Santiago H, Duby MM: Delayed distant metastasis from a subcutaneous sacrococcygeal ependymoma: Case report, with tissue culture ultrastructure observations, and review of the litrature. Cancer 30:10461067, 1972.
COMMENTS In this case report, Dr. Moser and associates have described a patient with an intradural mass lesion, which at surgery was discovered to be an ependymoma arising from within the L3 nerve root. They wisely decided to carry out a microsurgical removal of this tumor from within the nerve root, rather than transect the root, a decision that seems to have been justified by the fact that the patient was free of neurological deficit postoperatively. Since spinal ependymomas originate either from the ependymal lining of the central canal of the spinal cord or from the ependymal cell clusters of the filum terminale, they almost always present either as intermedullary spinal cord tumors or as tumors of the region of the conus medullaris and cauda equina. On rare occasions, such tumors can arise in ectopic locations within the sacrococcygeal region. Such extra-spinal ependymomas usually arise either
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anterior to the sacrum (in either the pelvic or abdominal cavity) or posterior to the sacrum in the subcutaneous tissue of the back. There are, however, occasional cases of ectopic ependymoma the origin of which is more difficult to explain. Thus, two cases have been described as occurring within the broad ligament of the ovary, and most importantly, Russell and Rubinstein (1) refer to one previous example of a circumscribed ependymoma that was successfully excised from the second lumbar nerve root. Since that patient was reported to have survived free of symptoms for at least 11 years, one can reasonably hope that the patient described in this report will have a similarly long recurrence-free postoperative course. Robert A. Morantz Kansas City, Missouri REFERENCES: (1) 1.
Russell DS, Rubinstein LJ: Pathology of Tumors of the Nervous System. Baltimore, Williams & Wilkins, 1989, ed 5, p 716.
Although ependymomas quite commonly involve the central nervous system, it is certainly extremely rare for one of these tumors to occur outside the central nervous system. These authors describe a case of an ependymoma found in a peripheral spinal nerve root in a patient whose magnetic resonance images of the head and, apparently, of the cervical and thoracic spine were unremarkable. The myelogram also seems not to have shown anything to suggest that this might be a drop metastasis, and for this reason, the authors felt that this was an ependymoma arising from the L3 root. The authors remind us of the fact that ependymomas can arise outside the central nervous system, and since the advent of magnetic resonance imaging, we can be more confident that we are not dealing with a metastatic lesion but, in fact, an extracentral nervous system lesion. In the discussion, the authors also mention the extradural sacral ependymoma, which I personally have only recently seen in a single patient. I expect that if an ependymal remanent of the primitive neural tube can result in extradural sacral ependymomas, a focus of ectopic ependymal tissue could result in the formation of a neoplasm at other unexpected locations along the neural axis. I do think that the authors were correct to proceed with removal of this lesion for a very satisfactory outcome. I do note that in the discussion, the authors state that the possibility of this being some type of a benign lesion may have inappropriately delayed surgery. I suspect, however, that most surgeons would have operated on such a lesion in a 31-year-old woman who was experiencing progressive symptoms, and I doubt that the possibility of more benign lesions in the differential diagnosis would have
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
to the filum on the various imaging studies should indicate the unusual nature and extramedullary origin of this lesion. However, extension of a conal ependymoma could assume a similar appearance. We believe that this is the first reported case of an ependymoma originating from completely within a spinal nerve root. The imaging studies clearly demonstrate the nerve root origin of this tumor. The lesion was removed completely without damage to the nerve root or spinal cord.
caused most surgeons to delay surgery. Because of the possibility of microscopic residual ependymoma resulting in recurrent disease and also because of the possibility that there conceivably still could be some occult primary lesion, I think it will be very important to monitor this patient periodically during the next several years. Fortunately, this process is much easier since the advent of magnetic resonance imaging.
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Michael J. Ebersold Rochester, Minnesota
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Figure 2. Oblique view of the upper lumbar spine obtained during myelography. Contrast material outlines the superior extent of the mass (open arrows) and the filum (solid arrow).
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Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 1. T1-weighted, saggital magnetic resonance image of the lumbar spine demonstrates a mass (arrow) of intermediate signal intensity inferior to the filum.
Figure 4. Photomicrograph of the surgial specimen demonstrating perivascular rosettes (hematoxylin and eosin).
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Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 3. Axial computed tomographic myelograms: A, superior aspect of the mass, separate from the filum (curved arrow); B, a more caudal section showing the eccentric position of the mass and its extension toward the neural foramen.
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mass was seen bulging at the L2-L3 region, displacing the nerve roots of the cauda equina. Decompression was performed, and at this point it became clear that the lesion was actually arising from within the L3 nerve root. Since the patient had no presurgical motor deficit, a decision was made not to resect the nerve root. Using microsurgery, resection of the tumor was performed. The patient tolerated the procedure well, with no complications nor any postoperative neurological deficit. Histological examination showed the mass to be typical of myxopapillary ependymoma (Fig. 4). DISCUSSION Fifty to sixty percent of spinal cord tumors of glial origin are ependymomas (3). Most commonly, these tumors involve the lower portion of the spinal cord, including the conus medullaris, filum terminale, and cauda equina, where ependymomas constitute close to 90% of the primary tumors (5). Intracranial ependymomas have their origin in the cells lining the ventricles and choroid plexus. In the spinal cord, they arise from the ependymal cells lining the central canal or its remnants and from the cells of the ventriculus terminalis in the filum terminale. Ependymomas rarely occur outside the central nervous system. These may be primary presacral tumors (4), metastasis or direct extension of a primary central nervous system tumor to adjacent tissue (6), or subcutaneous, sacrococcygeal tumors that may or may not connect to the spinal cord (2). Extradural sacral ependymomas are thought to arise from the coccygeal medullary vestige, a remnant of the primitive neural tube lined with ependymal tissue (1) . There is no known connection between this structure and the nerve roots to explain the presence of ependymal tissue in a peripheral nerve root, as in the case described here. One would have to postulate that during embryonic development, a focus of ectopic ependymal tissue was formed, and later gave rise to neoplasm. Twenty to thirty percent of ependymomas in ectopic locations are associated with spina bifida occulta, indicating developmental failure that resulted additionally in ectopic ependymal rests. In our patient, no associated anomalies were detected. Imaging of spinal ependymomas by computed tomographic myelography or by magnetic resonance imaging demonstrates an intradural, intramedullary mass, for which the prime differential diagnoses are ependymoma and astrocytoma. Signal characteristics are similar for both lesions: low on T1- and high on T2-weighted images. If the mass is large enough, it may be difficult to discern whether the lesion is intramedullary or extramedullary. This is true especially with ependymomas arising from the filum terminale or conus medullaris and extending into the extramedullary space. The differentiation of such a lesion from a meningioma or neurofibroma may be difficult, and is based on the appearance of the lesion relative to the cord, nerve roots, and filum. A preoperative diagnosis of a benign lesion such as a neurofibroma might be entertained, delaying treatment. The eccentric position of the mass relative
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Neurosurgery 1992-98 November 1992, Volume 31, Number 5 962 Ependymoma of the Spinal Nerve Root: Case Report Case Report
Received, November 18, 1991. Accepted, June 8, 1992. Reprint requests: Franklin G. Moser, M.D., Department of Imaging, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048. REFERENCES: (1-6) 1. 2.
3. 4. 5.
6.
Bale PM: Ependymal rests and subcutaneous sacrococcygeal ependymoma. Pathology 12:237- 243, 1980. Helwig EB, Stern JB: Subcutaneous sacrococcygeal myxopappilary ependymoma: A clinicopathologic study of 32 cases. Am J Clin Pathol 81:156-161, 1984. Kernohan JW, Fletcher-Kernohan EM: Ependymomas: A study of 109 cases. Assoc Res Nerv Ment Dis 16:182-209, 1935. Morantz RA, Kepes JJ, Batinsky S, Masterson BJ: Extraspinal ependymomas: Report of three cases. J Neurosurg 51:383-391, 1979. Sonnenfeld PRL, Scheithauer BW, Onofrio BM: Myxopappilary ependymoma: A clinicopathologic and immunohistochemical study of 77 cases. Cancer 56:883-893, 1985. Wolff M, Santiago H, Duby MM: Delayed distant metastasis from a subcutaneous sacrococcygeal ependymoma: Case report, with tissue culture ultrastructure observations, and review of the litrature. Cancer 30:10461067, 1972.
COMMENTS In this case report, Dr. Moser and associates have described a patient with an intradural mass lesion, which at surgery was discovered to be an ependymoma arising from within the L3 nerve root. They wisely decided to carry out a microsurgical removal of this tumor from within the nerve root, rather than transect the root, a decision that seems to have been justified by the fact that the patient was free of neurological deficit postoperatively. Since spinal ependymomas originate either from the ependymal lining of the central canal of the spinal cord or from the ependymal cell clusters of the filum terminale, they almost always present either as intermedullary spinal cord tumors or as tumors of the region of the conus medullaris and cauda equina. On rare occasions, such tumors can arise in ectopic locations within the sacrococcygeal region. Such extra-spinal ependymomas usually arise either
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/962/2281035 by University of Sydney Library user on 26 March 2018
anterior to the sacrum (in either the pelvic or abdominal cavity) or posterior to the sacrum in the subcutaneous tissue of the back. There are, however, occasional cases of ectopic ependymoma the origin of which is more difficult to explain. Thus, two cases have been described as occurring within the broad ligament of the ovary, and most importantly, Russell and Rubinstein (1) refer to one previous example of a circumscribed ependymoma that was successfully excised from the second lumbar nerve root. Since that patient was reported to have survived free of symptoms for at least 11 years, one can reasonably hope that the patient described in this report will have a similarly long recurrence-free postoperative course. Robert A. Morantz Kansas City, Missouri REFERENCES: (1) 1.
Russell DS, Rubinstein LJ: Pathology of Tumors of the Nervous System. Baltimore, Williams & Wilkins, 1989, ed 5, p 716.
Although ependymomas quite commonly involve the central nervous system, it is certainly extremely rare for one of these tumors to occur outside the central nervous system. These authors describe a case of an ependymoma found in a peripheral spinal nerve root in a patient whose magnetic resonance images of the head and, apparently, of the cervical and thoracic spine were unremarkable. The myelogram also seems not to have shown anything to suggest that this might be a drop metastasis, and for this reason, the authors felt that this was an ependymoma arising from the L3 root. The authors remind us of the fact that ependymomas can arise outside the central nervous system, and since the advent of magnetic resonance imaging, we can be more confident that we are not dealing with a metastatic lesion but, in fact, an extracentral nervous system lesion. In the discussion, the authors also mention the extradural sacral ependymoma, which I personally have only recently seen in a single patient. I expect that if an ependymal remanent of the primitive neural tube can result in extradural sacral ependymomas, a focus of ectopic ependymal tissue could result in the formation of a neoplasm at other unexpected locations along the neural axis. I do think that the authors were correct to proceed with removal of this lesion for a very satisfactory outcome. I do note that in the discussion, the authors state that the possibility of this being some type of a benign lesion may have inappropriately delayed surgery. I suspect, however, that most surgeons would have operated on such a lesion in a 31-year-old woman who was experiencing progressive symptoms, and I doubt that the possibility of more benign lesions in the differential diagnosis would have
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
to the filum on the various imaging studies should indicate the unusual nature and extramedullary origin of this lesion. However, extension of a conal ependymoma could assume a similar appearance. We believe that this is the first reported case of an ependymoma originating from completely within a spinal nerve root. The imaging studies clearly demonstrate the nerve root origin of this tumor. The lesion was removed completely without damage to the nerve root or spinal cord.
caused most surgeons to delay surgery. Because of the possibility of microscopic residual ependymoma resulting in recurrent disease and also because of the possibility that there conceivably still could be some occult primary lesion, I think it will be very important to monitor this patient periodically during the next several years. Fortunately, this process is much easier since the advent of magnetic resonance imaging.
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Michael J. Ebersold Rochester, Minnesota
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/962/2281035 by University of Sydney Library user on 26 March 2018
Figure 2. Oblique view of the upper lumbar spine obtained during myelography. Contrast material outlines the superior extent of the mass (open arrows) and the filum (solid arrow).
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/962/2281035 by University of Sydney Library user on 26 March 2018
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 1. T1-weighted, saggital magnetic resonance image of the lumbar spine demonstrates a mass (arrow) of intermediate signal intensity inferior to the filum.
Figure 4. Photomicrograph of the surgial specimen demonstrating perivascular rosettes (hematoxylin and eosin).
Downloaded from https://academic.oup.com/neurosurgery/article-abstract/31/5/962/2281035 by University of Sydney Library user on 26 March 2018
Redistribution of this article permitted only in accordance with the publisher’s copyright provisions.
Figure 3. Axial computed tomographic myelograms: A, superior aspect of the mass, separate from the filum (curved arrow); B, a more caudal section showing the eccentric position of the mass and its extension toward the neural foramen.
