Wernicke Encephalopathy
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Direct answer
Acute thiamine (vitamin B1) deficiency — classically encephalopathy (confusion, apathy, disorientation), ophthalmoplegia (abducens palsies, horizontal gaze palsy, nystagmus) and gait ataxia, although only a minority show all three — is Wernicke encephalopathy, a clinical emergency treated empirically with high-dose parenteral thiamine before any glucose infusion. Untreated or late-treated disease converts to Korsakoff syndrome, the largely irreversible amnestic state; think of it in alcohol use disorder, hyperemesis gravidarum, bariatric surgery, refeeding and dialysis.
What you must remember
- The triad is the exception, not the rule — perhaps a third or fewer show all three elements, so any two (or even one, with the right risk factor) in a vulnerable patient deserves empirical thiamine.
- Vulnerable states beyond alcohol: hyperemesis gravidarum, anorexia and starvation, bariatric surgery and prolonged vomiting, refeeding after malnutrition, dialysis, severe heart failure, AIDS and malignancy.
- Ocular findings are the most specific: nystagmus (horizontal, with vertical on lateral gaze), lateral rectus (sixth nerve) weakness, conjugate gaze palsies; pupils are involved only rarely and late.
- Ataxia is predominantly a disorder of stance and gait (wide-based, unstable) with the arms relatively spared; peripheral neuropathy may coexist and muddy the picture.
- MRI (when obtained): symmetric T2/FLAIR hyperintensity in the mammillary bodies, medial thalami, periaqueductal grey, floor of the fourth ventricle and around the third ventricle — mammillary body involvement being the classic teaching point; chronic cases show mammillary atrophy.
- Treatment: high-dose parenteral thiamine (commonly 200–500 mg intravenously three times daily for several days) — oral thiamine is inadequate in the acute state because intestinal absorption is impaired in deficiency.
- Sequence saves brains: thiamine before or with glucose, always — glucose oxidation consumes thiamine and can precipitate or worsen the encephalopathy; magnesium is a required cofactor and its deficiency must be corrected or thiamine fails to work.
- Response is diagnostic as well as therapeutic: ocular signs improve within hours to days, confusion over days to weeks, gait more slowly; absent nystagmus and amnesia may persist.
- Korsakoff syndrome follows untreated or recurrent Wernicke: disproportionate anterograde and retrograde amnesia with confabulation, requiring supported long-term care; a substantial fraction of Wernicke survivors are left with some Korsakoff impairment.
One emergency bay encounter
A 44-year-old man with long-standing alcohol dependence is brought in drowsy and confused; he has vomited for two days and eaten little. He is disoriented to place, his eyes show horizontal nystagmus with a weak right lateral rectus, and he cannot stand without pitching backward. No triad-gazing is needed — two elements in a starved alcoholic is already the diagnosis, and the treatment reflexes are ordered. First: intravenous thiamine 200–500 mg now, before the glucose that his erratic finger-prick (62 mg/dL) seems to demand — glucose first is the error this encounter exists to prevent. Second: magnesium level checked and replaced, because thiamine-dependent enzymes stall without it, and hypomagnesaemia is near-universal in this population. Third: glucose, fluids and electrolytes after thiamine is running, with B-complex continuation and gradual refeeding (feeding a malnourished patient aggressively without thiamine is the refeeding trap repeating itself). Fourth: look for the precipitants — infection, head injury, hepatic encephalopathy as the alternative driver, and withdrawal risk. Fifth: watch the therapeutic timeline — the nystagmus and gaze palsy largely resolve within days; if they do not, revisit the diagnosis. And sixth: the prognosis conversation — because he presented with confusion, his risk of Korsakoff syndrome is real, and memory testing before discharge plus thiamine continuation, alcohol treatment referral and dietary rehabilitation are what stand between him and the amnestic ward.
Where students slip
Three slips recur. The sequence error — dextrose before thiamine — is the most-punished single fact in this territory. The second is expecting the full triad before acting: the teaching point is that the triad is present in a minority, and the risk factor plus any compatible sign justifies empirical treatment. The third is the magnesium nuance — treating thiamine deficiency while magnesium remains low produces a non-responder, and examiners ask specifically why thiamine "fails" in alcoholic patients. Finally, candidates forget that Wernicke occurs in non-drinkers: the pregnant woman with hyperemesis and the post-bariatric patient are the favourite atypical stems.
Frequently asked questions
What is the classic triad of Wernicke encephalopathy?
Encephalopathy (acute confusional state), ophthalmoplegia with nystagmus, and gait ataxia — although only a minority of patients manifest all three simultaneously.
Why must thiamine precede glucose administration?
Glucose oxidation consumes thiamine; in a deficient patient a glucose load precipitates or aggravates Wernicke encephalopathy — give thiamine before or with every dextrose infusion.
Which MRI findings support the diagnosis?
Symmetric T2/FLAIR hyperintensities in the mammillary bodies, medial thalami, periaqueductal grey and floor of the fourth ventricle — though imaging may be normal and treatment must never await it.
What is the relationship between Wernicke and Korsakoff syndromes?
Korsakoff syndrome — anterograde-dominant amnesia with confabulation — is the chronic, largely irreversible stage that follows untreated or inadequately treated Wernicke encephalopathy.
Which non-alcoholic conditions predispose to thiamine deficiency?
Hyperemesis gravidarum, bariatric surgery and prolonged vomiting, starvation and anorexia, refeeding after malnutrition, dialysis, and prolonged intravenous feeding without supplementation.