The MRI manifestations of Hashimoto's Encephalopathy (HE) can vary from normal appearance, ischemic lesions, demyelination, vasogenic edema to atrophy. The diverse MRI features of HE reported in the literature made it difficult to understand the pathological process and monitoring the prognosis. To investigate the dynamic changes of MRI manifestations in HE, two cases of HE were retrospectively analyzed with a series of longitudinal MRI data, including T2 weighted image (T2WI), T1 weighted image (T1WI), fluid attenuated inversion recovery image (FLAIR), diffusion weighted image and diffusion tensor image(DT1). Although similar acute ischemic manifestations were observed at the onset of HE in both cases, at follow-up, we observed different evolutions of HE on MRI between the two cases. It might partially account for the diversity of MRI findings (for example, a certain stage of HE). Clinical and MRI findings at follow-up also indicated that early treatment contributed to the recovery of lesions. (C) 2010 Elsevier B.V. All rights reserved.