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Neuroradiology Case of the Week

Case 345

August 2008

Harshabad Singh, MBBS, Balasubramanya Kolar,MD
and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is 43-old-female who presented with acute mental status changes and obtundation. Previous MRI performed at an outside center showed periventricular and pontine abnormalities. MRI with angiogram is requested to evaluate for multiple sclerosis or stroke due to vasculitis

Imaging Findings: There was bilateral symmetrical hyperintensity involving the mammillary bodies with enhancement in addition to periventricular and pericallosal hyperintense lesions.

Diagnosis: Wernicke encephalopathy

Discussion: Wernicke encephalopathy (WE) is a serious neurological disorder caused by thiamine (vitamin B1) deficiency. The disease is due to deficiency of vitamin B1 and occurs mostly in alcoholics, but also in case of hyperemesis gravidarum, prolonged infectious-febrile conditions, GI carcinoma, anorexia nervosa and prolonged voluntary starvation [1]. The true prevalence of WE is clearly higher than is diagnosed clinically, since pathognomonic lesions have been found in up to 2.2% of consecutive series of autopsies in adults. It would seem that the prevalence of the disease is not influenced by the sex of the patients, though it is slightly higher in males. The age of onset ranges from 30 to 70 years [2]. The typical clinical presentation is characterized by ophthalmoplegia, ataxia, nystagmus and disturbances of consciousness. In many cases, however, clinical presentation is incomplete and only changes in consciousness are present. If untreated, WE may be followed by an amnestic syndrome or Korsakoff psychosis [1].
     MR findings were represented by symmetric hyperintensity on T2-weighted and fluid-attenuated inversion recovery (FLAIR) images; symmetric hypointensity or no abnormalities on T1-weighted images; and symmetric areas of contrast-enhancement after gadolinium injection involving the medial thalamus, periventricular region of the third ventricle, periaqueductal area, mammillary bodies, tectal region, and dorsal medulla [3]. The thalamic hyperintensities are more marked on diffusion-weighted images than on T2-weighted and FLAIR images. The clear demonstration of thalamic lesions is important for the diagnosis and follow-up because of the frequent involvement of the thalamus in WE. In comparison to conventional imaging, therefore, diffusion-weighted imaging could offer a potential diagnostic advantage in some patients with WE [4].
     There have been very few reports of proton MR spectroscopy in cases of WE. The findings varied but an increased level of lactate was consistent in both the reports which can be explained on the basis of decreased cerebral alpha-ketoglutarate dehydrogenase activity (a thiamine dependant enzyme system) which promotes anaerobic metabolism thus raising local tissue lactate levels [5].
     Follow up imaging of patients with WE may reveal lower intensities or fewer regions of hyperintensity than previously noted and brain volume loss.The volume loss may be diffuse or focal involving the third ventricle, cerebral aqueduct, mammillary bodies, cerebellar vermis and is revealed as third ventricle enlargement with aqueductal dilatation and mammillary body atrophy [2,4].
     Hyperintensities on T2-weighted and FLAIR images are not specific to this pathology and could represent edema and/or demyelination along with gliosis. Therefore, differential diagnosis could include demyelinating/dysmyelinating disease, such as multiple sclerosis, Behcet’s disease, or central pontine or extrapontine myelinolysis. However, demyelinating diseases can be excluded due to their asymmetrical distribution, while central pontine myelinolysis mainly involves pontine basis without an association with the fourth ventricle [6].
     Periventricular and pericallosal lesions which were oriented perpendicular to the lateral ventricles were noted in our case. These lesions supported a demyelinating etiology. However, the symmetric involvement of the mammillary bodies suggested possible Wernicke’s encephalopathy in this patient with an underlying demyelinating disorder. The thiamine levels were low and corroborated this possibility.
     Influenza A virus infection, primary acute disseminated encephalomyelitis, cytomegalovirus encephalitis, primary cerebral lymphoma, variant Creutzfeldt-Jakob disease, and West Nile virus meningoencephalitis represent other possible differential diagnoses of symmetric medial thalamic lesions [3].
     Because the classic clinical triad is present in only 16% of cases, other paraclinical methods have become extremely important. The combination of conventional MR imaging with some of its new developments, such as diffusion-weighed imaging and proton MR spectroscopy, seems to constitute a powerful diagnostic tool for early diagnosis and treatment of patients with Wernicke encephalopathy.

References:

1. Weidauer S, Nichtweiss M, Lanfermann H, Zanella FE. Wernicke encephalopathy: MR findings and clinical presentation. Eur Radiol. 2003 May;13(5):1001-9. [PubMed]
2. Gallucci M, Bozzao A, Splendiani A, Masciocchi C, Passariello R. Wernicke encephalopathy: MR findings in five patients. AJNR Am J Neuroradiol. 1990 Sep-Oct;11(5):887-92. [PubMed]
3. Zuccoli G, Gallucci M, Capellades J, et al. Wernicke encephalopathy: MR findings at clinical presentation in twenty-six alcoholic and nonalcoholic patients. AJNR Am J Neuroradiol. 2007 Aug;28(7):1328-31. [PubMed]
4. White ML, Zhang Y, Andrew LG, Hadley WL. MR imaging with diffusion-weighted imaging in acute and chronic Wernicke encephalopathy. AJNR Am J Neuroradiol. 2005 Oct;26(9):2306-10. [PubMed]
5. Rugilo CA, Uribe Roca MC, Zurru MC, Capizzano AA, Pontello GA, Gatto EM. Proton MR spectroscopy in Wernicke encephalopathy. AJNR Am J Neuroradiol. 2003 May;24(5):952-5. [PubMed]
6. Bae SJ, Lee HK, Lee JH, Choi CG, Suh DC. Wernicke's encephalopathy: atypical manifestation at MR imaging. AJNR Am J Neuroradiol. 2001 Sep;22(8):1480-2. [PubMed]