Most common tumour of the posterior cranial fossa is -

Gliomas account for 60% of brain tumours, with the aggressive glioblastoma multiforme (WHO grade IV) the most common glioma, followed by meningiomas (20%) and pituitary tumours (10%). Although the lower-grade gliomas (I and II) may be very indolent, with prognosis measured in terms of many years, these may transform to higher-grade disease at any time, with a resultant sharp decline in life expectancy Ref Harrison 20th edition pg2258