Detectability of Ischemic Lesions on Diffusion-Weighted Imaging Is Biphasic after Transient Ischemic Attack

BackgroundExperimental studies of transient focal ischemia indicate biphasic detectability of lesions by diffusion-weighted imaging (DWI); poorly detectable phase exists at 1-12 hours after reperfusion. The present study aimed to clarify whether poorly detectable phase also exists in DWI of transient ischemic attack (TIA) patients.MethodsA retrospective study was conducted in 144 consecutive TIA patients who underwent magnetic resonance imaging (MRI) within 2 weeks after carotid TIA. Patients were classified into 9 groups according to time from disappearance of TIA symptoms to DWI: intraischemic period, 0-1 hour, 1-12 hours, 12-24 hours, 1-2 days, 2-3 days, 3-7 days, 7-10 days, and 10-14 days after the end of TIA.ResultsLesions were detected in 33 of 144 patients (22.9%). The frequency of positive lesions was 20% in the intraischemic period and 30.8% at 0-1 hour after the end of TIA; it markedly decreased to 8.7% at 1-12 hours after end of TIA. Thereafter, it increased to 21.7%, 30.8%, 36.4%, 37.0%, 38.5%, and 30% at 12-24 hours, 1-2 days, 2-3 days, 3-7 days, 7-10 days, and 10-14 days after the end of TIA, respectively. In 7 patients, MRI was repeated twice, at 1-12 hours and then at 5-13 days after the end of TIA. Lesions were never detected on the first MRI but were clearly demonstrated in 4 of 7 patients on the second MRI.ConclusionsThe detectability of ischemic lesions may be biphasic after TIA as indicated by experimental studies.