Case contributed by Ammar Haouimi


Signs of raised intracranial pressure.

Patient Data

Age: 9 years
Gender: Female

Pre and post contrast CT


Midline mass of the posterior cerebral fossa of vermian location, hyperdense to the brain parenchyma with areas of cystic change/necrosis and heterogeneous enhancement on post-contrast images. Surrounding vasogenic edema with effacement of the fourth ventricle, basal cisterns and obstructive hydrocephalus.


On the MRI sequences, the vermian mass appears iso-to hypointense to the cortical grey matter on T1, iso-to hyperintense on T2/FLAIR, containing areas of cystic change/necrosis with heterogeneous enhancement following IV contrast and restricted diffusion within the solid component (the ADC value of the tumor is around 554 x 10-6 mm2/s, lower than normal cerebellum. No calcification or hemorrhagic component is seen.

Moderate surrounding vasogenic edema with a mass effect on the brainstem and fourth ventricle with tonsillar herniation. Dilated third and lateral ventricles with transependymal edema (obstructive hydrocephalus).

The MRS shows elevated choline and decreased NAA.

Case Discussion

CT and MRI of a midline posterior fossa mass centered on the cerebellar vermis with tonsillar herniation and obstructive hydrocephalus, most consistent with medulloblastoma.

On imaging, the main differential diagnoses in the pediatric population include:

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