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A 43 x 36 x 31 mm mass arises from the cerebellar vermis and extends more to the left than the right. Superiorly it abuts the left tentorium cerebelli. There is associated mass-effect with compression of the fourth ventricle and the aqueduct so that there is acute hydrocephalus with trans-ependymal oedema. There is flattening of the pons and extension of the cerebral tonsils into the foramen magnum.
The lesion is heterogeneous in signal intensity with multiple cystic or necrotic areas; the larger superior portion of the lesion is predominately solid, with rim enhancing cystic component inferiorly. The solid components enhance fairly homogeneously. Along the posterior margin of the lesion there are multiple flow voids indicating that the lesion is vascular. Although broadly abutting the tentorium cerebelli, there is no dural tail of enhancement or diffusion restriction. Small volume of perilesional T2 hyperintensity extending into the left middle cerebellar peduncle.
Scattered T2 hyperintense foci noted in cerebral white matter. No further enhancing lesion.
Vascular tumour arising from the cerebellar vermis with severe posterior fossa mass effect and hydrocephalus. Differential include haemangioblastoma and vascular metastasis. Given the size and broad abutment of tentorium, but less likely possibility is a large atypical meningioma or haemangiopericytoma severely indenting the posterior aspect of the cerebellum.