T1 hyperintense posterior fossa cystic lesion

Case contributed by Dr Marianne Kuehnast


HIV-positive patient. Presented with severe headache, ophthalmoplegia and multiple cranial nerve palsies.

Patient Data

Age: 35 years
Gender: Female

A large, lobulated, homogenous, hyperdense extra-axial mass is evident in the prepontine cistern, extending into the spinal canal through the foramen magnum, resulting in compression of the pons and midbrain as well as attenuation of the fourth ventricle.

A large, lobulated extra-axial mass is evident in the prepontine and interpeduncular cistern, extending through the foramen magnum into the anterior spinal canal up to the inferior aspect of the C2 vertebral body. The mass extends into the middle cranial fossa on the right side via Meckel's cave and into the posterior aspect of the suprasellar cistern on the right side. The mass also extends up to the CP angles bilaterally.

It results in compression of the pons and medulla oblongata and attenuation of the fourth ventricle, but no hydrocephalus. Within the spinal canal, the mass results in spinal cord compression.

The mass encases both vertebral arteries as well as the basilar artery. It causes medial displacement of the right posterior communicating artery.

On T1WI, the mass is hyperintense but is isointense to white matter on T2WI. It is of inhomeogenous signal intensity on FLAIR and does not enhance post contrast. Fluid restriction is demonstrated on diffusion weighted imaging (DWI) and corresponding apparent diffusion coefficient (ADC).

Case Discussion

This case represents an example of a large T1 hyperintense cystic lesion of the posterior fossa.

The differential includes a white epidermoid or a neurenteric cyst.

In this case, the high T1 signal is due to a high protein content. On T2WI, the mass is relatively hypointense (isointense to white matter). Alternatively, the high T1 signal may be due to high lipid content or due to hemorrhage. 

This pattern is opposite to that of a typical epidermoid cyst i.e. T1 hypointense and T2 hyperintense, but is seen in so-called white epidermoids

A neurenteric cyst is the most likely alternative diagnosis in this case.

Unfortunately, our patient passed away before a biopsy could be taken for a definitive histological diagnosis to be made.


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Case information

rID: 51239
Published: 13th Feb 2017
Last edited: 14th Aug 2019
Tag: asnr017
Inclusion in quiz mode: Included

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