Ependymoma Workup

Updated: Apr 14, 2015
  • Author: Jeffrey N Bruce, MD; Chief Editor: Jules E Harris, MD, FACP, FRCPC  more...
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Workup

Laboratory Studies

No laboratory studies are helpful in making the diagnosis of ependymoma.

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Imaging Studies

Ependymomas have some characteristic features on CT scan and MRI that help narrow the differential diagnosis. Whenever possible, patients in whom an ependymoma is suspected should undergo MRI with and without administration of intravenous contrast. [26]

Intracranial ependymoma

Intracranial ependymomas are typically isodense on unenhanced CT scans with minimal to moderate enhancement upon contrast administration. Calcification can be noted on unenhanced CT scans in approximately one half of cases. Cyst formation is common in these tumors, and foraminal spread can be observed in posterior fossa lesions through the foramina of Luschka and Magendie.

On precontrast and postcontrast MRI, tumors often appear heterogeneous secondary to necrosis, hemorrhage, and calcification. Variable signal intensity is noted on T1- and T2-weighted images, although intracranial ependymomas are usually hypointense to isointense on T1-weighted images and hyperintense compared with gray matter, on T2-weighted images. See the images below.

CT scan without contrast. Fourth ventricle ependym CT scan without contrast. Fourth ventricle ependymoma.
CT scan without contrast. Fourth ventricle ependym CT scan without contrast. Fourth ventricle ependymoma. Note blood in the fourth ventricle.
CT scan without contrast in the patient with fourt CT scan without contrast in the patient with fourth ventricle ependymoma. Blood has refluxed into the third and lateral ventricles.
CT scan without contrast in the patient with fourt CT scan without contrast in the patient with fourth ventricle ependymoma. Note blood traversing foramina.
T1-weighted MRI. Rare case of a fourth ventricle e T1-weighted MRI. Rare case of a fourth ventricle ependymoma presenting as an intraventricular bleed.
T1-weighted MRI without contrast demonstrating epe T1-weighted MRI without contrast demonstrating ependymoma located in the fourth ventricle.
T2-weighted MRI demonstrating ependymoma in the fo T2-weighted MRI demonstrating ependymoma in the fourth ventricle.
Coronal T1-weighted MRI with contrast demonstratin Coronal T1-weighted MRI with contrast demonstrating ependymoma of the fourth ventricle.

Spinal ependymoma

Most intramedullary tumors are isointense or slightly hypointense to the surrounding spinal cord on T1-weighted images. Often, only subtle spinal cord enlargement is evident. T2-weighted images are more sensitive because most tumors are hyperintense to the spinal cord on these pulse sequences. T2 studies are not particularly specific and may not distinguish the solid tumor from polar cysts. Nearly all intramedullary neoplasms enhance on T1-weighted contrast examinations.

Ependymomas usually demonstrate uniform contrast enhancement and are located symmetrically within the spinal cord. Polar cysts are identified in the majority of cases, particularly in the setting of cervical or cervicothoracic tumors. Heterogeneous enhancement from intratumoral cysts or necrosis can also be observed.

In some cases, contrast enhancement of a cystic ependymoma may be minimal. In these cases, distinguishing these tumors from intramedullary astrocytomas is difficult.

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Procedures

See the list below:

  • Lumbar puncture (LP) is generally contraindicated in the setting of a brain tumor because of the risk of transtentorial herniation secondary to increased intracranial pressure. CSF studies do not aid significantly in the diagnosis of ependymomas, with the possible exception of determining leptomeningeal spread in children with posterior fossa tumors. Yet even in this case, spinal MRI performed with and without contrast enhancement is a more optimal study for such a determination. In the case of spinal ependymoma, CSF obtained from LP may show elevated protein levels.
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Histologic Findings

Ependymoma (WHO grade II) pathology includes cellular, papillary, and clear cell variants, as well as anaplastic ependymomas (WHO grade III), myxopapillary ependymomas (WHO grade I), and subependymomas (WHO grade I) (see the images below). Histologically, ependymomas are characterized by ependymal pseudorosettes with glial fibrillary acidic protein (GFAP)–positive processes tapering toward blood vessels. Myxopapillary ependymomas are located at the cauda equina and conus, while subependymoma and anaplastic ependymomas are described at intramedullary locations. See the images below.

Gross surgical specimen of a fourth ventricle epen Gross surgical specimen of a fourth ventricle ependymoma.
Histologic study of a classic ependymoma. Note the Histologic study of a classic ependymoma. Note the characteristic perivascular pseudorosettes.
Cellular ependymoma. Cells with a high nuclear-cyt Cellular ependymoma. Cells with a high nuclear-cytoplasmic ratio. Few pseudorosettes or paucicellular areas are present.
Myxopapillary ependymoma. Clusters of loosely arra Myxopapillary ependymoma. Clusters of loosely arranged cuboidal cells separated by pools of mucin.
Clear cell ependymoma. Round cells with cytoplasmi Clear cell ependymoma. Round cells with cytoplasmic clearing. This may mimic an oligodendroglioma.

A variety of histologic ependymoma subtypes may be encountered. The cellular ependymoma is the most common, but epithelial, tanycytic (fibrillar), subependymoma, myxopapillary, or mixed examples also occur. Histologic differentiation from astrocytoma may be difficult, but the presence of perivascular pseudorosettes or true rosettes establishes the diagnosis. Most spinal ependymomas are histologically benign, although necrosis and intratumoral hemorrhage are frequent. Although unencapsulated, these glial-derived tumors are usually well circumscribed and do not infiltrate adjacent spinal cord tissue. Recent attempts to correlate the expression of MIB-1 antigen with malignancy of ependymomas have been confounded by tumor heterogeneity. Myxopapillary ependymoma histology consists of a papillary arrangement of cuboidal or columnar tumor cells surrounding a vascularized core of hyalinized and poorly cellular connective tissue.

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Staging

No conventional staging criteria exist for intracranial or spinal ependymomas. Postoperative MRI is recommended within 48 hours of tumor resection to assess presence of residual tumor and to facilitate adjuvant treatment planning. In the case of children with ependymomas of the fourth ventricle, a surveillance spinal MRI is often recommended to rule out seeding.

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Electroencephalography

Electroencephalography (EEG) performed on a patient with a supratentorial ependymoma may show generalized, diffuse slowing and/or epileptogenic spikes over the area of the tumor. However, no findings on EEG are specific for ependymoma.

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