Centred on the posterior wall of the fourth ventricle is a T2 FLAIR hyperintense, minimal enhancing lesion causing localised mass effect with nearly complete effacement of the fourth ventricle. The lateral and third ventricles are, however, normal in calibre, with no evidence of hydrocephalus. The lesion demonstrates low ADC values (~600 x 10^-6 mm^2/s) indicating high cellularity. No abnormal susceptibility.
Multiple punctate white matter lesions which are T2 FLAIR hyperintense and T1 hypointense are scattered throughout both cerebral hemispheres.
Conclusion:
Minimally enhancing lesion centred on the fourth ventricle with low ADC values is favoured to represent a medulloblastoma.