Abstract
We describe a patient presented with clinically a small cerebellar ischaemic stroke but required emergency decompression within 24 hours of symptoms onset after incidental finding of severe mass effect on imaging without any change in her mild clinical symptoms. Her initial multimodal acute stroke imaging, non-contrast CT of the brain and CT angiography from aortic arch to vertex were normal. CT perfusion showed a very small deficit only. The malignant mass effect was picked on an MRI scan performed routinely as part of a clinical trial, 32 hours after stroke. Our case highlights stroke evolution, and mass effect may be insidious and faster than anticipated in the posterior fossa. Cerebellar stroke of any severity diagnosed clinically and radiologically may benefit from routine follow-up imaging at 24 hours from onset.