Characteristics of patients with minor ischaemic strokes and negative MRI: a cross-sectional study

Background: Diffusion weighted (DWI) MRI is recommended in UK guidelines to evaluate minor strokes, yet can produce negative results. Objective: We determined the rate of negative MRI (including DWI) and associated features in patients presenting to hospital with minor strokes. Methods: We performed a prospective observational cross sectional study in a teaching hospital of patients with a clinical diagnosis of ischaemic lacunar or minor cortical stroke. We performed MRI (DWI, T2, FLAIR, T2* and T1) as soon as possible after presentation. We used multivariate analysis to determine predictors of negative DWI and MRI (all sequences). Gold standard for clinical diagnosis of stroke was the opinion of an expert panel. Results: We recruited 246 patients, mean age 68.1 years (SD 11.6 years), 162 were males (66%) and the median NIHSS was 2 (range 0-8). The median time from stroke onset to MR scan was 12 days (IQR 4-27 days). Eighty-one patients (33%) did not show any ischaemia on DWI. Sixty patients (24%) did not show the recent infarct on MRI (DWI/T2/FLAIR). With multivariate analysis, less severe stroke, younger age, female gender and increased time from stroke onset to scan were associated with negative DWI. With multivariate analysis, younger age and female gender were associated with negative MRI (DWI or T2 or FLAIR) scans. Conclusions: There is a high rate of negative MRI and DWI amongst patients with minor stroke (a third) which has important management and research implications. A negative MRI or DWI does not exclude the diagnosis of stroke.