General MRI presentation of ependymoma
Ependymoma presents as an expansive mass leading to local enlargement of the spinal cord. An extensive edema zone typically forms around the tumor node.
Basic MRI characteristics:
- On T1WI, the signal from the lesion is isointense or slightly hypointense.
- On T2WI, the appearance is highly heterogeneous. The tumor contains both solid and cystic areas, and low-signal zones may be identified within the nodule itself.
- Administration of gadolinium typically reveals focal nodular contrast enhancement in the central divisions of the spinal cord.
Specific marker: cap sign
Ependymomas (primarily Grade 2) are most characterized by the so-called cap sign (cap sign).
It is visualized on T2-weighted images as bilateral hypointense areas that appear to cap the superior and inferior poles of the tumor node. This is one of the most reliable signs for suspecting ependymoma on initial scanning.
Myxopapillary ependymoma
This is a specific tumor variant with well-defined borders and a heterogeneous structure. Typical localization is at the level of the third lumbar vertebra (L3).
Imaging features of the myxopapillary variant:
- T1WI: The signal is slightly hyperintense, which is explained by mucin accumulation within the tissue structure.
- T2WI: The lesion shows a low signal. A dark rim is frequently visualized at the periphery of the nodule, indicating prior intratumoral hemorrhage.
- Contrast-enhanced T1WI: Active gadolinium enhancement by the tumor tissue is noted.
Impact on the spinal cord and CSF pathways
Myxopapillary ependymoma significantly disrupts cerebrospinal fluid dynamics and the anatomy of adjacent tissues:
- Caudal (inferior) to the tumor: Blockage of the CSF pathways occurs. The accumulation of «trapped» cerebrospinal fluid yields a hyperintense (bright) signal on both T1 and T2. This is due to the pathologically high protein content in the blocked CSF.
- Rostral (superior) to the tumor: Extensive cyst formation is observed, causing the spinal cord to locally expand and thicken. Pronounced edema develops at the border with unchanged neural tissue.
Differentiating from spinal cord astrocytomas
In differential diagnosis, it is important to distinguish ependymomas from astrocytomas. Regardless of the grade of malignancy, astrocytomas have an infiltrative growth pattern with poorly defined borders, making total resection usually impossible. They are most commonly localized in the thoracic region (almost 70%).
In children, astrocytomas can involve long segments, creating a «holocord» appearance (involvement of the entire length), which is usually driven by extensive edema rather than the tumor tissue itself. Structurally, they may appear as a «cyst with a mural nodule», have necrotic-cystic degeneration zones (60%), or be entirely solid.
Unlike ependymomas, gadolinium enhancement in astrocytomas is variable and does not define true tumor margins: low-grade fibrillary variants often do not enhance at all, high-grade variants enhance unevenly (patchily), and pilocytic variants enhance intensely. The walls of accompanying syringomyelic cavities do not enhance. Intratumoral hemorrhage in astrocytomas is better visualized on GRE T2*. Indirect manifestations are also typical for children with intradural tumors: scoliosis and hyperkyphosis.
Briefly: answers to topical questions
What histological types of spinal cord ependymomas exist according to the WHO classification?
According to the cited excerpt of the WHO classification, ependymal tumors include:
- Subependymoma (Subependymoma).
- Myxopapillary ependymoma (Myxopapillary ependymoma) — typically localized in the region of the conus medullaris, filum terminale, and cauda equina.
- Ependymoma (Ependymoma), including papillary ependymoma (Papillary ependymoma).
Ependymoma is also characterized by the cap sign, especially in Grade 2.
What other tumors, besides astrocytoma, must spinal cord ependymoma be differentiated from?
In addition to astrocytoma, spinal cord ependymoma is differentiated from other intramedullary neoplasms and tumor mimics:
- Hemangioblastoma (Haemangioblastoma), associated with von Hippel–Lindau syndrome.
- Ganglioglioma (Ganglioglioma), encountered in children.
- Metastases.
- Tumor mimics — demyelinating diseases, including multiple sclerosis and neuromyelitis optica.
What is the surgical treatment strategy for spinal cord ependymomas depending on their margins?
The surgical treatment strategy for spinal cord ependymomas is determined by their growth pattern and margin definition. Since ependymomas are relatively well-demarcated from healthy tissues, complete removal is feasible.
| Characteristic | Ependymoma | Astrocytoma (for comparison) |
|---|---|---|
| Boundaries | Clear borders | Poorly defined borders |
| Growth pattern | Expansive mass | Infiltrative growth pattern |
| Surgical approach | Complete resection possible | Total resection impossible, biopsy is usually performed |
«The ependymoma wears a cap in the center» — remember that the tumor typically grows expansively from the center of the cord and features a characteristic cap sign (hypointense zones at the poles on T2WI).
Class and exam questions
What is the cap sign and what is it typical for?
The cap sign is bilateral hypointense zones at the poles of the tumor on T2-weighted images. This is the most typical sign for ependymomas (especially Grade 2).
Why does myxopapillary ependymoma show high signal on T1-weighted images without contrast?
A slightly hyperintense signal on T1WI is associated with the presence of mucin within the structure of this tumor type.
What happens to the CSF caudal to a myxopapillary ependymoma?
A block of the CSF pathways forms. The fluid accumulated below the tumor has a high protein content, thus yielding a hyperintense signal on T1WI and T2WI.
How does spinal cord astrocytoma enhance with contrast compared to ependymoma?
Contrast enhancement of astrocytomas is highly variable and does not reflect true margins (low-grade may not enhance, high-grade enhance patchily), whereas ependymoma produces distinct focal nodular enhancement in the center.
What else to study on this topic
- Pilocytic and fibrillar spinal cord astrocytomas: epidemiology, histology, and prognosis in children and adults.
- Infiltrative growth pattern of astrocytomas and surgical treatment options.
- MRI phenomenon "holocord" (total involvement of the spinal cord length) and the role of concomitant edema.
- Necrotic-cystic component and the «cyst with a mural nodule» appearance in intramedullary tumors.
- Indirect signs of intradural tumors in children: scoliosis and hyperkyphosis.
Master the entire topic in the "Diagnostic Radiology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Spinal Cord Ependymoma" and 2,199 more pages on the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 10 video lessons on the subject
Other topics in the "Spine" section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.