<prompt> Most common tumour of the posterior cranial fossa is -GliomaMedulloblastomaMeningiomaOligodendroglioma  <response>: 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 