I would bet that every emergency physician has missed cases of Wernicke encephalopathy. I almost certainly have. The early findings can be subtle and easily confused with those of frequent concomitant conditions such as alcoholism or infection. Without a high index of suspicion in patients who are malnourished or have other risk factors, the clinician can easily make the cognitive error of anchoring on an obvious diagnosis (for example, alcohol withdrawal) and failing to include Wernicke encephalopathy in the differential.
Wernicke encephalopathy is an acute syndrome involving various neurological deficits caused by thiamine deficiency and the resulting abnormalities in carbohydrate metabolism. Thiamine (vitamin B1) is a cofactor essential for several steps in the Krebs cycle and the efficient aerobic utilization of glucose to form ATP. After thiamine is depleted, glucose is metabolized through anaerobic pathways, causing focal lactic acidosis, edema, and cellular malfunction in certain key areas of the central nervous system. Promptly depleting thiamine is a critical intervention, essential to preventing progression to irreversible neurological impairment and Korsakoff psychosis.
Certain misconceptions and myths concerning Wernicke encephalopathy make the diagnosis more likely to be missed.
Myth 1: Wernicke encephalopathy is quite rare. This condition is not frequently diagnosed, but it is actually more common than one would imagine. Some sources suggest the prevalence is two percent in the general population and up to 12.5 percent in chronic alcoholics. Older studies indicated that the diagnosis was first made at autopsy in more than 80 percent of cases. Whatever the exact figures, Wernicke encephalopathy is not at all the type of rare condition one sees only once or twice in a career.
Myth 2: Wernicke encephalopathy occurs only in chronic alcoholics. It's true that it is diagnosed most often in patients with chronic alcohol abuse, but it can occur in anyone who is malnourished and whose thiamine is depleted. The range of conditions that increase the risk for Wernicke encephalopathy is broad: alcohol abuse, malignancy, hyperemesis gravidarum, anorexia nervosa, prolonged total parenteral nutrition without thiamine repletion, iatrogenic glucose loading in any predisposed patient, AIDS, and hemodialysis. (Ann Emerg Med. 2007;50:715.) It is increasingly being recognized in patients who have undergone gastric bypass surgery.
Myth 3: The diagnosis of Wernicke encephalopathy depends on the presence of the classic triad. The German neuropathologist Carl Wernicke described the first three cases in 1881. These were all found on autopsy and, by definition, at the extreme end of the spectrum. Before death, all three patients had exhibited some degree of altered mental status, ophthalmoplegia, and ataxia—the classic triad.
In fact, Wernicke encephalopathy often presents in a less extreme fashion, and the triad is seen in only about 16 percent of cases. Eye findings can take various forms, with horizontal nystagmus the most common. Total ophthalmoplegia is rare. Manifestations of altered mental status can range from slight confusion to coma. Ataxia and inability to walk are often mistakingly attributed to nonspecific weakness caused by the patient's generally poor medical condition. (Table.)
Caine, et al., proposed new operational criteria for identifying Wernicke encephalopathy, specifically in chronic alcoholics, that require the presence of only two of these symptoms: dietary deficiencies, oculomotor abnormalities, cerebellar dysfunction, and altered mental status or memory impairment (J Neurol Neurosurg Psychiatry. 1997;62:51; http://bit.ly/2GnBC7N.) It is obvious that these criteria would be incredibly sensitive but not specific because just about every alcoholic patient with acute disease would likely have them. But keeping Caine's criteria in mind when assessing a patient at risk for Wernicke encephalopathy means the diagnosis won't be overlooked and inadvertently omitted from the differential. This will probably result in overdiagnosing and overtreating many patients who don't, in fact, have Wernicke encephalopathy, but empiric treatment with thiamine is quite safe.
Myth 4: Anaphylaxis is a significant risk when administering parenteral thiamine. Anaphylactic reactions occur but are quite rare. One source estimated that the risk is no more than one reaction per 250,000 intravenous doses (Intern Med J. 2014;44:911; http://bit.ly/2IziVji.) This small risk must be weighed against the chance of precipitating Korsakoff psychosis and irreversible cognitive deficits if a carbohydrate load (for instance, IV infusion of dextrose) is given to a patient with uncorrected thiamine deficiency.
No good evidence has established the optimal dose schedule when treating Wernicke encephalopathy, but the Royal College of Physicians in London and some other major groups recommend a starting dose of 500 mg IV in 100 mL normal saline given over 30 minutes every eight hours for several days. (Alcohol Alcohol. 2002;37:513.) A good response to thiamine repletion, with rapid improvement in oculomotor abnormalities and other neurological deficits, helps confirm the diagnosis. Thiamine can be administered at a lower dose after the first few days of treatment as long as clinical improvement continues. An initial prophylactic dose of 100 mg thiamine IV is reasonable in potentially malnourished patients who are not suspected of having acute Wernicke encephalopathy.
Myth 5: The presence of an alternate diagnosis rules out the possibility of Wernicke encephalopathy. Practitioners who believe this particular myth are, not infrequently, called defendants. In fact, acute medical conditions such as infection accelerate metabolism and can bring on thiamine deficiency. It's all too easy to attribute altered mental status to pneumonia or meningitis, but doing so can be a critical error.
A Texas jury awarded $14.3 million in 2017 to a 35-year-old woman who claimed her physician failed to prevent, diagnose, and treat Wernicke encephalopathy that began after she developed intractable vomiting following gastric bypass surgery. (Puente v. Virlar.) A recent Google search for “Wernicke encephalopathy” and “malpractice” returned many hits from law firms specializing in thiamine deficiency and trolling for cases. Despite what one feels about the current medical-legal environment, I think we can agree that emergency clinicians should be at least as aware of Wernicke encephalopathy as the plaintiff's bar is.
Dr. Gussowis a voluntary attending physician at the John H. Stroger Hospital of Cook County in Chicago, an assistant professor of emergency medicine at Rush Medical College, a consultant to the Illinois Poison Center, and a lecturer in emergency medicine at the University of Illinois Medical Center in Chicago. Read his blog atwww.thepoisonreview.com, follow him on Twitter @poisonreview, and read his past columns athttp://bit.ly/EMN-ToxRounds.Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.