Background and Purpose - Many patients with transient ischemic attack (TIA) or minor stroke present to medical attention after a delay of several days or weeks, at which time it may be more difficult to obtain a clear history and clinical signs may have resolved. Because ischemic lesions on diffusion- weighted MRI (DWI) often persist for several weeks, we hypothesized that adding DWI to a standard protocol with T2- weighted imaging might be useful in the management of patients presenting late. Methods - We studied consecutive patients with TIA or minor stroke presenting ≥ 3 days after the event. Two independent observers recorded the presence or absence of recent ischemic lesions on 2 different occasions, first with the T2 scan only, and second with T2 and DWI. Each time, with the aid of a written clinical summary, the observers recorded their diagnosis and proposed management. Results - 300 patients (159 men) were scanned at a median of 17 (interquartile range=10 to 23) days after symptom onset. DWI showed a high signal lesion in 114/164 (70% ) minor strokes versus 17/136 (13% ) TIAs (P < 0.0001). The presence of high- signal lesions on DWI decreased nonlinearly with time since symptom onset (F < 0.0001) and increased with National Institutes of Health Stroke Score (P=0.038) and with age (P=0- 01). In 90/206 (43.7% ) patients with 1 or multiple lesions on T2, DWI helped to clarify whether these were related to a recent ischemic event (79 [48% Abstract: strokes; 11 [31% Abstract:- TIAs). Compared with T2 alone, DWI provided additional information in 108 (36% ) patients (91 [56% Abstract: strokes and 17 [13% Abstract: TIAs), such as clarification of clinical diagnosis (18 patients, 6% ) or vascular territory (28 patients, 93% ), which was considered likely to influence management in 42 (14% )- patients (32 [19% Abstract: strokes; 10 [7.4% Abstract: TIAs). Conclusions - The clinically useful information available from DWI provides a further justification for an MRI- based imaging protocol in patients with subacute TIA or minor stroke.
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