[Diffusion MRI for evaluating TIA--a case of reversible ischemic injury in the territory of the deep perforators].

A 61-year-old man was admitted to our hospital because of left pure motor hemiparesis. Neuroradiological examination was performed after three hours of onset, but no apparent lesion responsible for the hemiparesis was detected by CT and MRI. Diffusion weighted MRI (DWI), however, demonstrated a high signal area with good contrast in the posterior limb of right internal capsule. This lesion was compatible with patient's clinical symptoms. Apparent diffusion coefficient (ADC) of the lesion was lower than that of normal control at the timing of admission. On the following day within 24 hours after the onset, it was revealed that both left hemiparesis and high signal area on DWI had disappeared, and the ADC on the ischemic lesion was restored to normal level. Changes in the intensity on DWI corresponded well with reversion of ischemic injury, which suggested that DWI was very useful for diagnosis of TIA.