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Neuroradiology Case of the Day |
Long TR images (Figs. 2A,2B,2C) display hyperintense signal in the mamillary bodies, medial thalami, and surrounding the aqueduct and third ventricle. Gadolinium-enhanced T1-weighted MR images (Fig. 2D) show enhancement involving the mamillary bodies. These findings are typical for Wernicke's encephalopathy.
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Wernicke's encephalopathy results from vitamin B1 (thiamine) deficiency [1,2,3,4,5,6]. Most patients affected are malnourished alcoholics; however, Wernicke's encephalopathy has also been associated with other conditions such as gastrointestinal neoplasms, chronic dialysis, treatment with tolazamide, prolonged IV therapy without vitamin supplementation, bowel obstruction, hyperemesis gravidarum, and hematologic malignancy. Classic symptoms include ophthalmoplegia, nystagmus, ataxia, confusion, and apathy [1,2,3,4,5,6]. Korsakoff's syndrome is recognized as the more chronic stage of Wernicke's encephalopathy in approximately 80% of patients who have survived. Korsacoff's syndrome includes learning and memory deficits out of proportion to other cognitive functions [4, 5].
Patients with Wernicke's encephalopathy have lesions in the mamillary bodies, medial thalami, hypothalamus, and periventricular region (around the third ventricle and along the floor of the fourth ventricle). The mamillary bodies are most frequently affected. Occasionally, lesions contain petechial hemorrhage, but these hemorrhages are rarely large and conspicuous. Histopathologically, these lesions include edema, petechial hemorrhages, demyelination, and reactive astrocytosis. The capillaries swell and lipid-laden macrophages may be present in the perivascular spaces. In the chronic form (Korsakoff's syndrome) the mamillary bodies atrophy [1,2,3,4,5,6].
MR imaging is a highly sensitive method for detecting lesions associated with Wernicke's encephalopathy. The enhancement is thought to be a sign of acute stage of demyelination. If detected early, as in this case, the lesions are potentially reversible with thiamine supplementation [1,2,3, 6].
The other diagnoses are incorrect for various reasons. Marchiafava-Bignami disease is a disease occurring in alcoholics that results in demyelination of the central fibers of the corpus callosum and does not typically involve the mamillary bodies. It may be accompanied by degeneration of the anterior commissure, middle cerebellar peduncles, optic chiasm, and centrum semiovale.
Hallervorden-Spatz disease is a familial autosomal recessive disorder in which patients present with spasticity and dementia. It is associated with deposition of iron-containing substances in the globus pallidus, red nuclei, and substantia nigra. Typically, this desposition results in low signal intensity in these regions; however, high signal intensity in the globus pallidus and white matter has also been reported with this entity, giving an "eye of the tiger" appearance [4,5,6].
Wilson's disease is an autosomal recessive disorder in which copper is abnormally deposited in the liver and brain. It does not typically involve the mamillary bodies. Abnormal signal on T2-weighted MR imaging is observed in the putamen, caudate, thalamus, globus pallidus, dentate nucleus, pons, and mesencephalon [4,5,6].
Leigh disease is a neurodegenerative disorder resulting from a mitochondrial enzyme defect inherited in an autosomal recessive fashion. It usually presents in infancy (infantile form) but may present in childhood or, rarely, in adulthood. MR imaging may disclose nonenhancing high-signal-intensity lesions in the basal ganglia, periventricular white matter, corpus callosum, and brainstem. The mamillary bodies are typically spared [4,5,6].
References
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