Diffusion-weighted imaging abnormalities in wernicke encephalopathy: reversible cytotoxic edema?

BACKGROUND Wernicke encephalopathy (WE) is a metabolic disorder of the central nervous system resulting from vitamin B(1) deficiency. The exact mechanisms underlying the pathogenesis of the lesions in WE are not completely understood. Vitamin B1 deficiency is associated with intracellular and extracellular edema by glutamate(N-methyl-D-aspartate) receptor-mediated excitotoxicity. Conventional magnetic resonance imaging (MRI) cannot differentiate the types of edema. Diffusion-weighted imaging (DWI) has been reported to detect early ischemic damage (cytotoxic edema) as bright areas of high signal intensity (SI) and vasogenic edema as areas of heterogeneous SI. OBJECTIVES To describe the DWI findings and to characterize the types of edema in WE using DWI. SETTING Tertiary referral center. DESIGN AND METHODS Two patients with WE underwent DWI and conventional MRI with gadolinium enhancement. Wernicke encephalopathy was diagnosed with salient conventional MRI findings (high SIs in the paramedian thalamus, periaqueductal gray matter, and mamillary bodies) and typical clinical history and symptoms. Apparent diffusion coefficient (ADC) values were measured in abnormal lesions by visual inspection of DWIs and T2-weighted echo planar images. RESULTS T2-weighted and fluid-attenuated inversion recovery MRIs showed high SIs in the bilateral paramedian thalamus, mamillary bodies, and periaqueductal gray matter. The DWIs showed bright high SI in the corresponding lesions, and ADC values were decreased (patient 1: 512-545 x 10(-6)mm2/s; patient 2: 576-612 x 10(-6)mm2/s). The ADC decrease and the DWI high SI were normalized in 2 weeks with administration of thiamine hydrochloride. CONCLUSIONS Abnormalities on DWI and ADC decrease became normalized with adequate therapy. The MRI abnormalities in WE might be owing to the "reversible cytotoxic edema" caused by vitamin B1 deficiency.