Frequency of emerging positive diffusion-weighted imaging in early repeat examinations at least 24 h after transient ischemic attacks.

INTRODUCTION: The relationships between diffusion lesions and risk scores for patients with a Transient ischemic attack (TIA) and the optimal timing for diffusion lesion screening have not been characterized. The purpose of our study was to evaluate the appearance of diffusion-weighted imaging (DWI) lesions during follow-up examinations of patients with TIA or minor stroke without initial DWI lesions. METHODS: We identified 31 patients who did not show diffusion lesions in initial DWI. A second magnetic resonance imaging (MRI) examination was performed 24 h after the initial MRI, and the patients were divided into two groups based on the results. Demographic and clinical data, including initial National Institutes of Health Stroke Scale scores, ABCD and ABCD(2) scores, and other MRI findings were evaluated. The data were analyzed using Spearman's rank tests and unpaired t tests. RESULTS: Ten patients (32.3 %) showed diffusion lesions on the second DWI examination. Both risk scores were higher in these patients compared with patients with negative results on follow-up DWI (P < 0.05, unpaired t test) and correlated with the length of the TIA (R s = 0.017, P < 0.05; R s = 0.003, P < 0.01; Spearman's rank test). CONCLUSION: Our results suggest that TIA patients with high-risk scores might be underestimated if the first MRI was performed within 24 h of symptom onset.