A stroke is a rapidly developing clinical symptoms and/or signs of focal and sometimes global loss of brain function, with symptoms lasting more than 24 hours or leading to death with no apparent cause other than that of vascular origin.New MR imaging methods have become available that are able to detect cerebral ischaemia at a very early stage of the pathological process. Diffusion MR imaging provides information about the disturbances of cellular water haemostasis, thus detecting the first elements of the pathophysiological cascade leading to ischaemic injury.