Asymptomatic Recurrent Cerebral Ischaemic Lesions on Diffusion-Weighted Imaging in the Subacute and Chronic Phase after Transient Ischaemic Attack or Minor Ischaemic Stroke

Introduction The risk of recurrent stroke can be as high as 10% in the first 7 days after transient ischaemic attack (TIA) or minor stroke [1] and is highest in patients with large artery atherosclerosis (LAA) compared to the other aetiological stroke subtypes [2] . However, trials of secondary stroke prevention often recruit patients after the high early risk period has passed [1, 3] and the rate of symptomatic vascular events is low. Diffusion-weighted MR brain imaging (DWI) is a highly sensitive and specific technique in the diagnosis of acute ischaemia [4] . Asymptomatic cerebral ischaemic lesions on DWI in the acute phase after TIA or minor stroke are more frequent than recurrent symptomatic stroke [5] and are associated with poor outcome [6] . Consequently, DWI lesions may be a useful surrogate marker of stroke risk. Indeed, trials of antiplatelet therapy in which recurrent lesions on DWI performed at 3 months after TIA or minor stroke will form part of a composite end-point are already being planned [7, 8] . DWI studies in the acute phase after TIA or minor stroke have suggested that lesion recurrence is positively associated with LAA 5, 9]. Furthermore, patients with multiple infarcts on baseline DWI and patients with early recurrent asymptomatic lesions are more likely to have further recurrent lesions on DWI at 3 months. [10] However, there are no data on the clinical predictors of recurrent DWI lesions in the chronic phase after TIA or minor stroke. Therefore, we performed serial DWI 1–9 months after a TIA or minor stroke in patients with risk factors for LAA who were not undergoing carotid endarterectomy (CEA). We compared lesion recurrence on DWI in patients with 1 50% versus ̂ 50% carotid stenosis.