Single lesion identified in the right side of the posterior fossa located peripherally is probably intra-axial but does abut the dura. This measures 2.3 cm in size and shows avid enhancement, associated with vasogenic oedema in the adjacent cerebellum. Prominent flow voids are noted at the periphery of the lesion, with some signal loss due presumably to prior haemorrhage. MR spectroscopy demonstrates prominent lipid peak. This mass effect pushes on the inferior aspect of the medulla oblongata and partially effaces the fourth ventricle with obstructive hydrocephalus and transependymal oedema.
Low-lying cerebellar tonsils consistent with an acquired chiari type I. Otherwise the brain is unremarkable. No white matter lesions are seen as brain. No extra-axial collection.
Conclusion:
In this age group, particularly in the absence of known systemic malignancy, a posterior fossa mass with prominent flow voids most likely represents a haemangioblastoma. Less likely alternative diagnoses include solitary metastasis.