Evaluation of Infratentorial Ependymomas in Children

Examination

• Physical examination and history: There are not any specific clinical findings suggestive of an infratentorial ependymoma specifically, but a mass lesion in the posterior fossa is on the differential diagnosis when children present with signs and symptoms of hydrocephalus, cerebellar signs, or cranial neuropathies as described below.
• Signs of hydrocephalus: Signs and symptoms such as lethargy, upgaze paresis, or a full fontanelle/splayed sutures in infants may be seen at presentation.
• Altered gait: Children with posterior fossa infratentorial ependymomas can have either profound or subtle alteration in gait at presentation.
• Cerebellar signs are less common: Frank signs of cerebellar dysfunction such as truncal or appendicular ataxia are less common.
• Cranial neuropathies: Cranial neuropathies may be present, particularly in laterally located tumors that involve the cerebellopontine angle.

Laboratory Tests

• Standard testing: Standard laboratory tests in preparation for surgery are performed.

Radiologic Tests

CT Scan

• Iso- to hyperdense with calcifications: Infratentorial ependymomas appear as isodense to hyperdense intraventricular masses with multifocal calcifications on CT scanning.
• Moderate enhancement: These tumors have moderate enhancement on brain CT scan.
• Axial brain CT scan of an ependymoma: This non-contrast CT scan in a 2 year-old girl shows an isodense posterior fossa ependymoma with multiple areas of calcification. Note the triventricular enlargement with periventricular edema consistent with obstructive hydrocephalus.

MRI

• Intraventricular: Infratentorial ependymomas are almost always located adjacent to the floor of the fourth ventricle with the body of the ventricle expanded around the tumor, and they are often quite large at the time of radiologic diagnosis (11, 12).
• Heterogeneous and hypointense on T1-weighted images: On MRI infratentorial ependymomas are typically heterogeneously hypointense on T1-weighted imaging. The heterogeneous features of ependymoma are caused by areas of necrosis, cysts, calcification, and hemorrhage.

 

• Heterogeneous gadolinium enhancement is common 

 

• T2-weighted MRI hypointense: Isointense to hypointense mass on T2-weighted images

 

• Extension out ventricular foramen: The high tendency of tumor to extend through the foramen of Luschka and Magendie is an important diagnostic characteristic of this tumor which can help us to differentiate it from other common tumors of fourth ventricle (medulloblastoma, astrocytoma, and choroid plexus papilloma) which do not typically extend in this manner (see image above).
• CSF metastasis needs to be ruled out: Total spine MRI evaluation with gadolinium is necessary in patients suspicious of posterior fossa ependymoma. Spinal dural enhancement or intradural mass can be found that confirms tumor progressing to the spinal canal.

Nuclear Medicine Tests

• Not indicated

Electrodiagnostic Tests

• Not indicated

Neuropsychological Tests

• Not required but useful: While neuropyschological testing does not have any specific role in the diagnosis, it is helpful in gauging the impact of surgery and subsequent treatments. Typically, neuropsychological testing is not possible at diagnosis when patients present with symptoms of obstructive hydrocephalus that require urgent treatment.

Correlation of Tests

• Imaging highly suggestive: The presence of a posterior fossa mass contiguous with the fourth ventricle floor, which is inhomogeneously iso- to hyperdense with areas of calcification on CT scan, is hypointense on T1-weighted MRI, has nonhomogeneous enhancement, and has a tendency for downward extension from the fourth ventricle to the cervical canal or cerebellopontine angle all suggest an infratentorial ependymoma.