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Neuroradiology

Ependymoma

slow growing tumour that arises either from the ependymal surface of the ventricular system or from ependymal cell rests within the nervous tissue.

They are common tumours in children, comprising about 10% of paediatric CNS, while intraspinal ependymomas are more often found in adults (see spinal cord ependymoma). Two thirds of the intracranial ependymomas are located in the infratentorial compartment.

Histologically they may have different subtypes but the most characteristic appearance is that of ependymal rosettes, similar to a normal ependymal lining. Different degrees of anaplasia may be encountered; macroscopically the tumour, when in the fourth ventricle, tends to conform to the ventricular cavity and extrude through the foramina of the fourth ventricle into the cisterns. Calcifications are not infrequent, while haemorrhage is rare.

The clinical presentation varies according to location, with posterior fossa signs, nausea, vomiting, headache, ataxia and cerebral hemispheric signs.

On CT ependymomas tend to be isodense to slightly hypodense with calcifications in less than 50% and mild to moderate inhomogeneous enhancement.

On MR the tumour is not sigificantly different in signal from other glial tumours of the brain, being slightly iso- to hypointense on T1-weighted images and moderately hyperintense on T2-weighted (Fig.1). The only characteristic finding is location and gross morphology when the tumour is within the fourth ventricle in the posterior fossa (Fig.2). Enhancement is mild to moderate and inhomogeneous.

GS

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Fig.1

a. MR, T1-weighted image. Large, inhomogenous, hypo-isointense tumour located almost completely within the left lateral ventricle at the level of the trigone. b. MR, T2-weighted axial image. The tumour is markedly hyperintense. c , d. MR, T1-weighted images following gadolinium injection. Marked enhancement of the solid components of the tumour; some cysts are better seen remaining hypointense. The left "sequestered" temporal horn is dilated.
Ependymoma, Fig.1 (a)
Ependymoma, Fig.1 (b)
Ependymoma, Fig.1 (c)
Ependymoma, Fig.1 (d)
Ependymoma, Fig.2 (a)
Ependymoma, Fig.2 (b)
Ependymoma, Fig.2 (c)
Ependymoma, Fig.2 (d)