[Thyrotoxic encephalopathy showing reversible diffusion-weighted imaging abnormalities].

A 31-year-old man was transferred to our emergency room (ER) with acute onset of high-grade fever and consciousness disturbance. His consciousness at ER was severely disturbed with restlessness. No apparent focal neurological signs were seen. MRI with diffusion-weighted images (DWI) showed high signal intensities at the corpus callosum, left cerebellar hemisphere, left deep white matter and right middle cerebellar peduncle. These lesions were low signals in apparent diffusion coefficient(ADC) map, indicating cytotoxic edema. EEG showed enhanced fast waves seen in predominantly frontal regions. CSF examination was normal except elevated initial pressure of 210 mmH2O. He was treated with high dose dexamethasone and acyclovir. His consciousness and high-grade fever with systemic inflammatory responses were dramatically improved after these treatments. Subsequent data showed hyperthyroidism with anti-thyroid stimulating hormone receptor antibodies. This case was thought to be a thyrotoxic encephalopathy with beneficial response to corticosteroid therapy. Abnormalities seen in DWI and EEG were normalized ten days later.