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Wernicke Encephalopathy Workup

  • Author: Philip N Salen, MD; Chief Editor: Robert E O'Connor, MD, MPH  more...
 
Updated: Oct 28, 2015
 

Approach Considerations

Patients with WE present with altered mental status and other neurologic abnormalities. Obtaining a detailed patient history, performing a detailed physical examination with a focus on the neurological exam, laboratory workup, and radiographic evaluation are essential to exclude other causes of central nervous system (CNS) dysfunction.

No specific laboratory test is available for diagnosing WE. WE is a clinical diagnosis, and normal electrolyte levels may give only false reassurance and delay therapy. This is particularly the case when malnutrition is likely to be present. The motto should be "If in doubt, treat," as administration of thiamine does not pose potential harm.

Moreover, neither a normal computed tomography (CT) scan nor a normal magnetic resonance imaging (MRI) scan of the brain rule out the presence of acute WE or chronic WKS.[13]

Although WE remains a clinical diagnosis with no characteristic abnormalities in diagnostic studies, the use of laboratory and radiographic tests remains important to exclude alternate or coexisting medical conditions. The patient’s history and initial evaluation guide the selection of these tests.

Tests to perform include the following:

  • Complete blood count (CBC) - Rules out severe anemias and leukemias as causes of altered mental status.
  • Serum glucose levels - To exclude hypoglycemia and hyperglycemia as causes of encephalopathy.
  • Liver function tests and ammonia levels- To exclude hepatic and some medicinal causes of encephalopathy.
  • Basic metabolic profile (BMP)- To exclude hyponatremia and uremia as causes of encephalopathy.
  • Pulse oximetry and/or arterial blood gas (ABG) measurement - Exclude hypoxia and hypercarbia as causes of encephalopathy.
  • Toxic drug screening - Excludes some causes of drug-induced altered mental status.
  • Consider lumbar puncture (LP) - Consider LP to exclude CNS infections, such as meningitis and encephalitis, if indicated.

Erythrocyte transketolase levels

Erythrocyte transketolase levels reliably detect thiamine deficiency but are not necessary for the diagnosis of WE. In the erythrocyte transketolase activity assay, the extent of thiamine deficiency is expressed in percentage stimulation compared with baseline levels (the thiamine pyrophosphate effect). Normal values range from 0-15%; a value of 15-25% indicates thiamine deficiency, and a value of greater than 25% indicates severe deficiency.[2]

Blood pyruvate and lactate measurements

Blood pyruvate and lactate measurements, although not specific for thiamine deficiency illnesses, are sensitive and helpful, as thiamine is a cofactor of the pyruvate dehydrogenase enzyme, an important enzyme in aerobic metabolism (i.e. the Kreb cycle).[2]

Electroencephalogram

Consider an electroencephalogram (EEG) if nonconvulsive status epilepticus is suspected as a potential cause of coma and altered mental status.

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Biomarkers

Biomarkers, including an assay for thiamine, are not typically available for timely diagnostic purposes. In addition, no study has clearly described the sensitivity, specificity, and accuracy of thiamine levels in relation to active disease.[5] However, the thiamine levels can help the clinician assuming care of the patient in ambiguous cases, and obtaining a thiamine level can be considered for diagnostic dilemmas.[6]

Complete discrimination of WE patients and controls has been reported for thiamine monophosphate, a dephosphorylation product of the coenzyme thiamine pyrophosphate. However, evidence is sparse, and thiamine assays have limited availability and usually do not allow for an immediate diagnosis.[9]

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Serum Electrolyte Levels

Alterations in serum electrolyte levels, such as hypernatremia or hypercalcemia, can cause encephalopathy and must be excluded.

One case series suggested that patients with WE may exhibit a distinctive acid-base pattern consisting of a primary metabolic acidosis in conjunction with a primary respiratory alkalosis. The primary metabolic acidosis is secondary to thiamine's role in aerobic metabolism and the Krebs cycle; without thiamine, aerobic metabolism cannot progress and metabolic products, including lactate and pyruvate, are produced, which result in an anion gap acidosis (see the Anion Gap calculator). The role of thiamine in causing a primary respiratory alkalosis is unclear.[5]

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Imaging Studies

CT scanning

A head CT scan is an essential initial test for emergency diagnosis of focal neurologic disease, such as intracerebral hemorrhage. In patients who are comatose, CT scan can detect not only intracranial lesions but also fractures of the skull and minute amounts of blood. However, with a reported 13% sensitivity for WE, CT of the head does not appear to be useful in screening for this syndrome.[13]

MRI

Thiamine is a cofactor of several enzymes involved in glucose metabolism and cerebral energy utilization, and its depletion results in the neuronal damage as seen on MRI, including T2 and fluid-attenuated inversion recovery hyper-intense signaling in the mammillary bodies, periventricular thalamus, and periaqueductal gray matter, as well as diffusion-weighted imaging to differentiate vasogenic from cytotoxic edema.[1]

MRI offers a technique to make a definitive diagnosis antemortem, but the sensitivity is poor, and obtaining an MRI for this indication is typically impractical and unnecessary in the emergency department (ED).[6]

Although the clinical evidence for the utility of MRI is based on a study in which the sample size was small, the reported sensitivity of MRI was 53% and the reported specificity was 93%, for acute and chronic WKS. Because of the low sensitivity of MRI for WE, particularly an acute presentation, and because many patients with WE may not exhibit diagnostic features on MRI, normal MRI results does not preclude the diagnosis of acute illness.[13]

The appearance of acute WE on MRI demonstrates abnormal hyper-density of the mammillary bodies and periaqueductal gray matter with associated abnormal enhancement on T1-weighted images.[15] In chronic WE and WKS, radiographic imaging, especially MRI, may be normal or may show mamillary body, cerebellar, and cerebral shrinkage, as well as symmetrical, low-density abnormalities in periventricular areas, the diencephalon, and the midbrain.[13] Such symmetrical lesions are uncommon in other cerebral encephalopathic disorders and are suggestive of WKS.[13]

Morphometric studies of MRI imaging confirm that patients with WKS show excessive mammillary body and cerebellar shrinkage, indicating that these are highly specific MRI findings for this kind of encephalopathy.[13]

The image below shows brain morphologic studies as demonstrated on MRI. A 60-year-old man presented with bilateral gaze-evoked nystagmus, severe ataxia, and memory impairment. Brain fluid-attenuated inversion recovery (FLAIR)–weighted MRI shows concurrent cytotoxic and vasogenic edema patterns. This case demonstrates cytotoxic and vasogenic edema that may occur at the same time in WE. These findings may result from different vulnerability of brain regions to thiamine deprivation and the corresponding time delay between the development of lesions.[16]

This MRI shows typical high signal intensities (SI This MRI shows typical high signal intensities (SIs) in the medial thalamus (A), periaqueductal gray (B), mamillary bodies (C), cerebellar vermis (B, C, D), and paravermian superior cerebellum (D). All the lesions represent high SIs on the DWI (E–H). The ADC images of the cerebellar vermis (K, L) and paravermian superior cerebellum (L) show low SIs (arrowheads), whereas other described areas (I, J) show iso-SIs (arrows). Image courtesy of Neurology. Apr 8 2008;70(15):e48.
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Contributor Information and Disclosures
Author

Philip N Salen, MD Clinical Professor, Department of Emergency Medicine, PA Program, DeSales University; Adjunct Clinical Associate Professor, Department of Emergency Medicine, Temple University School of Medicine; Research Director, Emergency Medicine Education, St Luke's Hospital

Philip N Salen, MD is a member of the following medical societies: American College of Emergency Physicians, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

J Stephen Huff, MD, FACEP Professor of Emergency Medicine and Neurology, Department of Emergency Medicine, University of Virginia School of Medicine

J Stephen Huff, MD, FACEP is a member of the following medical societies: American Academy of Neurology, American College of Emergency Physicians, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Robert E O'Connor, MD, MPH Professor and Chair, Department of Emergency Medicine, University of Virginia Health System

Robert E O'Connor, MD, MPH is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Association for Physician Leadership, American Heart Association, Medical Society of Delaware, Society for Academic Emergency Medicine, Wilderness Medical Society, American Medical Association, National Association of EMS Physicians

Disclosure: Nothing to disclose.

Additional Contributors

Peter MC DeBlieux, MD Professor of Clinical Medicine and Pediatrics, Section of Pulmonary and Critical Care Medicine, Program Director, Department of Emergency Medicine, Louisiana State University School of Medicine in New Orleans

Peter MC DeBlieux, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, Radiological Society of North America, Society of Critical Care Medicine

Disclosure: Nothing to disclose.

References
  1. Attard O, Dietemann JL, Diemunsch P, Pottecher T, Meyer A, Calon BL. Wernicke encephalopathy: a complication of parenteral nutrition diagnosed by magnetic resonance imaging. Anesthesiology. 2006 Oct. 105(4):847-8. [Medline].

  2. Fattal-Valevski A, Kesler A, Sela BA, et al. Outbreak of life-threatening thiamine deficiency in infants in Israel caused by a defective soy-based formula. Pediatrics. 2005 Feb. 115(2):e233-8. [Medline].

  3. [Guideline] Day E, Bentham PW, Callaghan R, Kuruvilla T, George S. Thiamine for prevention and treatment of Wernicke- Korsakoff Syndrome in people who abuse alcohol (Cochrane Review ). The Cochrane Library. 2013. 7:1-20.

  4. Donnino M. Gastrointestinal beriberi: a previously unrecognized syndrome. Ann Intern Med. 2004 Dec 7. 141(11):898-9. [Medline].

  5. Donnino MW, Miller J, Garcia AJ, et al. Distinctive acid-base pattern in Wernicke's encephalopathy. Ann Emerg Med. 2007 Dec. 50(6):722-5. [Medline].

  6. Donnino MW, Vega J, Miller J, et al. Myths and misconceptions of Wernicke's encephalopathy: what every emergency physician should know. Ann Emerg Med. 2007 Dec. 50(6):715-21. [Medline].

  7. Buscaglia J, Faris J. Unsteady, unfocused, and unable to hear. Am J Med. 2005 Nov. 118(11):1215-7. [Medline].

  8. Decker MJ, Isaacman DJ. A common cause of altered mental status occurring at an uncommon age. Pediatr Emerg Care. 2000 Apr. 16(2):94-6. [Medline].

  9. Aasheim ET. Wernicke encephalopathy after bariatric surgery: a systematic review. Ann Surg. 2008 Nov. 248(5):714-20. [Medline].

  10. Hung SC, Hung SH, Tarng DC, Yang WC, Chen TW, Huang TP. Thiamine deficiency and unexplained encephalopathy in hemodialysis and peritoneal dialysis patients. Am J Kidney Dis. 2001 Nov. 38(5):941-7. [Medline].

  11. Thomson AD, Cook CC, Touquet R, et al. The Royal College of Physicians report on alcohol: guidelines for managing Wernicke's encephalopathy in the accident and Emergency Department. Alcohol Alcohol. 2002 Nov-Dec. 37(6):513-21. [Medline].

  12. Azim W, Walker R. Wernicke's encephalopathy: a frequently missed problem. Hosp Med. 2003 Jun. 64(6):326-7. [Medline].

  13. Antunez E, Estruch R, Cardenal C, et al. Usefulness of CT and MR imaging in the diagnosis of acute Wernicke's encephalopathy. AJR Am J Roentgenol. 1998 Oct. 171(4):1131-7. [Medline].

  14. Attard O, Dietemann JL, Diemunsch P, Pottecher T, Meyer A, Calon BL. Wernicke encephalopathy: a complication of parenteral nutrition diagnosed by magnetic resonance imaging. Anesthesiology. 2006 Oct. 105(4):847-8. [Medline].

  15. Kaineg B, Hudgins PA. Images in clinical medicine. Wernicke's encephalopathy. N Engl J Med. 2005 May 12. 352(19):e18. [Medline].

  16. Roh JH, Kim JH, Koo Y, Seo WK, Lee JM, Lee YH, et al. Teaching NeuroImage: Diverse MRI signal intensities with Wernicke encephalopathy. Neurology. 2008 Apr 8. 70(15):e48. [Medline].

 
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This MRI shows typical high signal intensities (SIs) in the medial thalamus (A), periaqueductal gray (B), mamillary bodies (C), cerebellar vermis (B, C, D), and paravermian superior cerebellum (D). All the lesions represent high SIs on the DWI (E–H). The ADC images of the cerebellar vermis (K, L) and paravermian superior cerebellum (L) show low SIs (arrowheads), whereas other described areas (I, J) show iso-SIs (arrows). Image courtesy of Neurology. Apr 8 2008;70(15):e48.
 
 
 
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