Correspondence to

The natural history of acute stroke is well defined. Predicting outcome in individuals, however, remains difficult, because prognostic studies examining associations between clinical signs or syndromes and outcome differ in patient selection, timing and choice of neurological assessments and outcome measures. Accuracy has been disappointing. Osier in 1892 stated that the 'course of the disease... is dependent on the situation and extent of the lesion'. Until recently, it has not been possible to examine the stroke prognosis, using Osier's approach, with any great accuracy. The advent of diffusion weighted magnetic resonance imaging (DWI), which is highly sensitive to the pathophysiological changes underlying stroke, offers this possibility as it measures the site and extent of irreversible infarction. This review summarises the results of syndrome or sign-based predictive studies and shows how DWI may explain different outcomes in patients with identical neurological presentations, according to the 'situation and extent of the lesion'