CT and MRI of Wernicke's encephalopathy.

The purpose of this pictorial essay is to present the computed tomography (CT) and magnetic resonance imaging (MRI) findings of Wernicke's encephalopathy, a rare, severe, acute neurological syndrome due to thiamine (vitamin B1) deficiency, associated with high morbidity and mortality. The classical clinical triad, which includes ocular signs, altered consciousness and ataxia, can be found in only one-third of patients. Although chronic alcoholic patients are the most commonly affected, Wernicke's encephalopathy may complicate malnutrition conditions in nonalcoholic patients, in whom it is greatly underestimated. CT and above all MRI of the brain play a fundamental role in diagnosing the condition and ruling out other diseases. MRI is the most sensitive technique and is required in all patients with a clinical suspicion of Wernicke's encephalopathy. Medial thalami, mamillary bodies, tegmentum, periaqueductal region, and tectal plate are typical sites of abnormal MRI signal. The dorsal medulla, red nuclei, cranial nerve nuclei, cerebellum, corpus callosum, frontal and parietal cerebral cortex are less common sites of involvement although they are more frequently affected in nonalcoholic patients. Paramagnetic contrast material may help to identify lesions not otherwise visible.