AUTHOR AND EDITOR INFORMATION

Section 1 of 6  

• Authors and Editors
• Introduction
• Differentials
• MRI
• Multimedia
• References

INTRODUCTION

Section 2 of 6  

• Authors and Editors
• Introduction
• Differentials
• MRI
• Multimedia
• References

Background

Ependymomas are believed to account for 60% of all primary neoplasms of the spinal cord and filum terminale (Slooff, 1964). Intraspinal ependymomas are most easily grouped into 3 classes: intramedullary lesions, myxopapillary ependymomas, and metastases from an intracranial origin.

Pathophysiology

Most intraspinal ependymomas arise de novo. Although intramedullary and cauda equina tumors may arise from an intramedullary source, these origins are uncommon. Intraspinal ependymomas are believed to arise from the ependymal cells lining the central canal, from the ventriculus terminalis of the conus, from within the filum terminale, or from cerebrospinal fluid (CSF) dissemination (Moser, 1992).

Intramedullary ependymomas most commonly occur in the cervical and cervicothoracic part of the spinal cord (McCormick, 1990; Hoshimaru, 1999). Their arterial supply is most often derived from the anterior spinal artery.

Myxopapillary ependymomas arise almost exclusively in the region of the conus and filum terminale. They account for as many as 90% of tumors in the conus (Moelleken, 1992; Celli, 1993). Rarely, they may arise in an extradural postsacral location, presumably from the coccygeal medullary vestige (Morantz, 1979) (see Anatomy).

Mortality/Morbidity

Both intramedullary and myxopapillary ependymomas tend to grow slowly, without infiltration of the surrounding neural tissue. Metastasis from myxopapillary ependymomas in adults is rare; however, several cases of intracranial seeding from conus and/or filum myxopapillary ependymomas are reported (Woesler, 1998; al Moutaery, 1996). These tumors are more aggressive in children than in adults; the tumors may spread via the subarachnoid space, invade locally, or result in extraneural metastases (Graf, 1999).

In 1996, Rezai et al examined 140 patients with ependymomas and found that the following were significant risk factors for tumor metastasis: a location in the spine rather than in the brain (12.5% vs 9.6%), a young patient, a myxopapillary histologic finding, a high proliferative index, and incomplete resection. In 1994, Cervoni et al found that the duration of symptoms before surgery, the degree of resection, and the appearance of the tumor are closely related to the likelihood of recurrence.

Sacral ependymomas may behave aggressively, with direct bony invasion, and they may spread to the lymph nodes and distant organs (Schweitzer, 1992).

Sex

Myxopapillary ependymomas has a predilection for males. This observation is in contrast to a slight preponderance of females who have intramedullary ependymomas.

Age

The myxopapillary variant appears in patients who are younger than those with intramedullary ependymomas.

Anatomy

Intramedullary ependymomas most commonly occur in the cervical and cervicothoracic parts of the spinal cord (McCormick, 1990; Hoshimaru, 1999). The tumors are centrally located and well circumscribed and cause symmetric expansion of the cord. Their arterial supply is most often derived from the anterior spinal artery.

Ependymomas generally appear as reddish or purple-gray masses with numerous, small, superficial blood vessels. Sometimes, the tumors are encapsulated. Although cystic ependymomas are infrequently reported, associated reactive cysts occur with most intramedullary ependymomas (Fine, 1995). Hemorrhage often occurs at the outer margins of these tumors (McCormick, 1990).

Myxopapillary ependymomas arise almost exclusively in the region of the conus and filum terminale. Rarely, they may arise in an extradural postsacral location, presumably from the coccygeal medullary vestige (Morantz, 1979). Unlike the discrete fusiform intramedullary variety, myxopapillary ependymomas primarily appear as lobulated discrete masses adherent to the filum and secondarily appear in the nerve roots of the cauda equina and in the conus. Grossly, they appear moderately vascular, reddish to purplish, sausage shaped, and encapsulated. They frequently have peripheral hemorrhage and cystic degeneration.

Clinical Details

Intramedullary ependymomas have a clinical manifestation of neck or back pain and, less often, numbness or paresthesias (McCormick, 1990). Myxopapillary ependymomas typically cause nonspecific symptoms, most commonly low back pain and lower extremity radiculopathy and, much less frequently, lower extremity weakness or bladder dysfunction. Given the slow growth and well-circumscribed quality of these tumors, symptoms generally progress slowly, and patients often have a long history prior to diagnosis.

Complete surgical resection is the treatment for intraspinal ependymomas (McCormick, 1990; Epstein, 1993; Lee, 1998; Hoshimaru, 1999). Total resection is generally curative, without the need for postoperative irradiation. Preoperative imaging is essential in planning care beyond identification of the tumor.

Tumor dissemination precludes surgical cure and makes continued aggressive resection in the setting of waning intraoperative electrophysiologic recordings unwarranted. Likewise, in the presence of hydrocephalus or a large intracranial mass, the intracranial pathologic condition should be addressed before the spinal lesion is resected.

In 1999, Hoshimaru et al found that the degree of preoperative cord atrophy and arachnoid scarring, particularly in the case of thoracic tumors, is closely correlated with surgical morbidity. Epstein (personal communication) reported similar risk factors and additionally noted that very large or very small tumors may be associated with an outcome poorer than that of other tumors.

Preferred Examination

The initial imaging evaluation likely includes plain radiography of the spine. The images may demonstrate erosion of the pedicle or scalloping of the dorsal vertebral body surface. However, the yield of plain radiography is limited, and when clinical suspicion exists, MRI of the spine with and without gadolinium enhancement is the study of choice. MRI permits evaluation of the cord substance itself for masses and associated findings such as edema, hemorrhage, cyst, syringomyelia, and cord atrophy.

For myxopapillary tumors, both the brain and spine should be evaluated at MRI with and without gadolinium enhancement. Solitary intramedullary lesions are less frequently associated with intracranial spread; thus, cerebral imaging is less important.

Limitations of Techniques

The radiographic diagnosis of intraspinal tumors is indirect and nonspecific. Changes induced by the tumor may be observed in the adjacent tissues. The pedicles may appear flattened or concave, with an increased interpedicular distance as a result of chronic pressure resulting in bony atrophy. Similarly, scalloping of the posterior part of the vertebral bodies or thinning of the lamina with a widened spinal canal may be observed (McCormick, 1990). Scoliosis may be visible on plain radiographs. Finally, in rare cases, intratumoral calcification may be observed on radiographs.

Myelography may assist in localizing an intraspinal mass to the extradural, intradural extramedullary, or intradural intramedullary compartments. A centrally situated, regularly fusiform cord may be suggestive of an intramedullary ependymoma, whereas fusiform swelling in the cauda equina, particularly when it is large enough to result in bony erosion, and a blockage of contrast enhancement may be consistent with an ependymoma of the filum.

With a yield similar to those of plain radiography or myelography, CT findings are not conclusive for ependymoma. Nonspecific findings of canal widening, bony erosion, and a thickened cord or filum are suggestive of but not diagnostic for ependymoma.

DIFFERENTIALS

Section 3 of 6  

• Authors and Editors
• Introduction
• Differentials
• MRI
• Multimedia
• References

Other Problems to be Considered

Schwannomas

MRI

Section 4 of 6  

• Authors and Editors
• Introduction
• Differentials
• MRI
• Multimedia
• References

Findings

General findings

On T1-weighted images, ependymomas generally appear isointense relative to the normal cord, although they may appear hypointense (less common finding). Heterogeneity and hyperintensity on T1-weighted images may be consistent with a hemorrhagic component to the mass. On T2-weighted images, ependymomas are generally hyperintense relative to the normal cord. Ependymomas are homogeneously and intensely enhancing with the administration of a gadolinium-based contrast material (Fine, 1995). The tumor often has well-defined borders with contrast enhancement.

Hemosiderin

Hemorrhage or hemosiderin in or at the cranial or caudal margin of ependymomas is a common imaging finding. T2-weighted MRIs may demonstrate a low-signal-intensity rim around some tumors; this finding represents the hemosiderin. In 1995, Fine et al noted this finding in only 20% of tumors; this percentage is far lower than the 64% Nemoto et al reported in 1992. This hemosiderin cap is fairly suggestive of ependymomas (Lefton, 1998). With filum ependymomas, hemorrhagic products may be seen within the filum.

Cysts

In 1995, Fine et al observed that 1 of 25 tumors evaluated was cystic, but 14 had associated reactive cysts: Eleven cysts were rostral to the tumor; 10, caudal to the tumor; and 7, both rostral and caudal. All reactive cysts had signal intensity similar to that of CSF. The cysts were hypointense on T1-weighted MRIs and hyperintense on T2-weighted MRIs. These cysts did not enhance with the administration of contrast material. In 1995, Wippold et al examined 20 patients with myxopapillary ependymomas; of these, 3 had cystic tumors, and 2 had a syrinx. Rarely do the tumors themselves have a cystic appearance.

Tumor size and location

Cervical lesions average 4.2 vertebral segments in length, thoracic lesions average 3.1 segments, and filar tumors average 4.0 segments (Fine, 1995). Most often, intramedullary ependymomas occur in the cervical cord; fewer lesions are thoracic, and fewer still occur at the conus (Hoshimaru, 1999; Fine, 1995; McCormick, 1990). About 50% of intraspinal ependymomas occur at the cauda equina; these are predominantly of the myxopapillary subtype (Fischer, 1976). Multiple lesions occur much more often in this region, with a frequency of 15% (Wippold, 1995).

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.

As of late December 2006, the FDA had received reports of 90 such cases of NSF/NFD. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

False Positives/Negatives

The chief intramedullary lesions from which ependymomas must be distinguished are astrocytomas and hemangioblastomas.

Ependymomas of the filum must be distinguished from schwannomas, hemangioblastomas, and astrocytomas. Astrocytomas of the cord are infiltrative and have margins that are less sharp than those of the other lesions. Astrocytomas are less prone to hemorrhage and infrequently result in a hemosiderin cap. More often, astrocytomas are eccentric in location. Schwannomas may demonstrate a central area of poor enhancement.

Hemangioblastomas have prominent vascularity, as well as large reactive cysts, which are consistent with their intracranial appearance. MRI signal intensity characteristics of hemangioblastomas are similar to those of ependymomas. The tumor nodule, which is situated on a pial surface, may have more intense enhancement than that of ependymomas. Local edema of the cord is more impressive around hemangioblastomas than ependymomas. Flow voids are often visible in hemangioblastomas.

The distinction of schwannomas from filum ependymomas may be impossible; their signal intensity characteristics are interchangeable. In fact, the characteristics of schwannomas and ependymomas are nearly identical on T1-weighted, T2-weighted, and gadolinium-enhanced MRIs. Schwannomas more often assume a dumbbell configuration and result in an enlargement of the adjacent neural foramina. Likewise, when the tumors are small, the observation of an origin from a root in the cauda equina, rather than the filum, may aid in the distinction of schwannomas from myxopapillary ependymomas. The distribution of the roots of the cauda equina in the thecal sac may help in distinguishing the tumors: An ependymoma of the filum pushes the roots to the periphery of the thecal sac, whereas a schwannoma of the cauda more often pushes the roots together in an eccentric fashion.

Compared with ependymomas, schwannomas infrequently appear multilobulated. The periphery of schwannomas is strongly enhancing, but the tumors may have central areas with poor enhancement.

MULTIMEDIA

Section 5 of 6  

• Authors and Editors
• Introduction
• Differentials
• MRI
• Multimedia
• References

Media file 1:  T1-weighted sagittal gadolinium-enhanced MRI demonstrates an enhancing intramedullary cervical tumor with a caudal cyst.
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Media file 2:  Axial T1-weighted image demonstrates a homogenously enhancing tumor centrally located in the spinal cord.
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Media file 3:  T2-weighted sagittal image demonstrates the hemosiderin and caudal cyst associated with the tumor.
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Media file 4:  MRI demonstrates a heterogeneously enhancing tumor in the thoracic region. No associated cysts are present.
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Media file 5:  Axial T1-weighted image confirms the central location of the tumor.
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Media file 6:  Spine ependymoma.
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Media file 7:  T1-weighted gadolinium-enhanced image of a myxopapillary ependymoma shows that the tumor is located in the lumbar region and homogenously enhancing.
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Media file 8:  T2-weighted MRI demonstrates a myxopapillary ependymoma in the cauda equina.
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Media type:  MRI

REFERENCES

Section 6 of 6

• Authors and Editors
• Introduction
• Differentials
• MRI
• Multimedia
• References

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• Cervoni L, Celli P, Fortuna A, Cantore G. Recurrence of spinal ependymoma. Risk factors and long-term survival. Spine. Dec 15 1994;19(24):2838-41. [Medline].
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Article Last Updated: Feb 1, 2007