Wernicke-Korsakoff Mnemonic: COA Triad & Thiamine First

Wernicke-Korsakoff syndrome is brain injury from thiamine (vitamin B₁) deficiency: acute Wernicke encephalopathy, with confusion, ophthalmoplegia (often with nystagmus) and ataxia, which, if untreated, often progresses to chronic Korsakoff syndrome, dominated by anterograde amnesia and confabulation. The lesions sit around the third ventricle and cerebral aqueduct, classically in the mammillary bodies and dorsomedial thalamus. The treatment rule is IV thiamine before glucose, because a carbohydrate load in a thiamine-depleted patient can precipitate or worsen the encephalopathy. The "Hotel B1" memory palace below stores the whole picture in one walk-through.

The memory palace: "Hotel B1"

Picture a run-down hotel called B1 (thiamine). A malnourished guest stumbles in off the street. Walk through it in order: front desk, lobby, upstairs suite, basement, guest book.

1. Front desk: thiamine before the sugar. The clerk offers the guest a glass of sugar water, but the manager knocks it away and hands over the B1 room key first. Rule: in anyone at risk, give IV thiamine before IV glucose.

2. The lobby (acute Wernicke): C-O-A.

• Confusion: the guest doesn't know where he is and is drowsy, inattentive and indifferent.
• Ophthalmoplegia: his eyes are stuck like a broken elevator (lateral rectus weakness, gaze palsies), and nystagmus makes them bounce.
• Ataxia: he crosses the lobby with slow, short, wide-based steps, as if the floor were tilting.

3. Upstairs suite (chronic Korsakoff): the confabulation suite. The guest book has blank pages for everything since check-in (anterograde amnesia) and a few torn-out older pages (retrograde amnesia; remote memories are spared more than recent ones). He fills the gaps with confident invented stories (confabulation), not to deceive: he believes them. He seems apathetic and unconcerned.

4. Basement (the lesions): the shrunken mammoth statues. Two small statues, the mammillary bodies, have shriveled, and the dorsomedial thalamus lamp beside them flickers. The damage wraps symmetrically around the central corridors: the third ventricle, the aqueduct and the fourth ventricle.

5. Guest book (who gets it): alcohol use disorder, hyperemesis gravidarum, bariatric surgery, starvation and refeeding, anorexia nervosa, cancer, AIDS and dialysis.

Why thiamine, and why glucose makes it worse

Thiamine pyrophosphate is the cofactor for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase and branched-chain α-ketoacid dehydrogenase, and for transketolase in the pentose phosphate pathway (the enzyme cofactors are drilled in the pyruvate dehydrogenase cofactors mnemonic). Glucose metabolism depends on it, so a carbohydrate load, whether IV dextrose or refeeding after starvation, raises the demand for what little thiamine is left and can trigger Wernicke encephalopathy.

Alcohol makes deficiency likely in several ways at once: poor intake, impaired absorption from the gut, poor storage in the liver and increased demand. The wider spectrum of thiamine deficiency (dry and wet beriberi) is covered in the thiamine (beriberi and Wernicke) overview.

Wernicke vs Korsakoff side by side

The memory circuit these lesions interrupt is mapped in the limbic system overview.

Diagnosis and treatment

• Diagnosis is clinical. There is no specific test. Serum thiamine is not routinely measured, because a normal level doesn't exclude the disorder, and imaging, spinal fluid and EEG show no characteristic changes, although MRI can support the diagnosis. Labs such as glucose, electrolytes and liver tests help rule out other causes.
• Treat on suspicion. Eye signs are common and confusion is often present, but not every patient has all three findings, and Wernicke encephalopathy is thought to be underdiagnosed, partly because its symptoms overlap with alcohol-related delirium.
• Thiamine first, and parenterally. No single dosing regimen has been proven best. Merck's Wernicke chapter lists 100 mg IV or IM immediately, then daily for at least 3–5 days; its thiamine-deficiency chapter describes a common higher-dose regimen of 500 mg IV three times a day for 2 days, then 250 mg IV or IM daily for 5 more days, with other B vitamins. Either way, give it before IV glucose, not after.
• Correct magnesium. Magnesium is a cofactor in thiamine-dependent metabolism, so hypomagnesemia should be corrected. Add fluids, electrolytes and multivitamins; alcohol cessation is essential.
• Prevent it. Undernourished patients should get parenteral thiamine, particularly when IV dextrose is needed, and thiamine is prudent before treatment in anyone with a reduced level of consciousness.
• Korsakoff syndrome is treated with thiamine, magnesium and hydration, abstinence from alcohol and memory rehabilitation; severe cases often need residential care.

Don't confuse it with

Exam traps

• Glucose before thiamine is the classic wrong answer.
• Waiting for the full triad, an MRI or a thiamine level delays treatment of a medical emergency.
• Confabulation isn't lying or malingering; the patient unconsciously fills memory gaps and believes the story.
• Korsakoff syndrome can follow severe or repeated delirium tremens, even without a typical Wernicke episode first.
• Low magnesium should be corrected alongside thiamine.
• Not only alcohol: hyperemesis gravidarum, bariatric surgery, anorexia nervosa and parenteral nutrition without vitamins all cause it.

Worked example

Vignette. A 26-year-old woman at 12 weeks' gestation is admitted for hyperemesis gravidarum after 3 weeks of vomiting and is started on dextrose-containing IV fluids. On day 2 she is confused and unsteady. She has horizontal nystagmus, bilateral lateral rectus weakness and a wide-based gait. Fingerstick glucose is 110 mg/dL. What is the most appropriate next step?

Answer: Give IV thiamine immediately, correct magnesium if low, and give no further dextrose until thiamine is on board.

Why not the alternatives:

• Brain MRI first: it can support the diagnosis, but imaging may show no characteristic abnormality and must not delay treatment.
• Serum thiamine level: not routinely used, and a normal value doesn't exclude deficiency.
• Increase the dextrose infusion: more carbohydrate without thiamine can worsen the encephalopathy.
• Lorazepam: treats alcohol withdrawal, which doesn't fit this picture.
• Lactulose: treats hepatic encephalopathy; nothing here suggests liver disease.

Key takeaways

• Wernicke = acute C-O-A (confusion, ophthalmoplegia with nystagmus, ataxia); Korsakoff = chronic amnesia with confabulation.
• Lesions: mammillary bodies and dorsomedial thalamus, around the third ventricle and aqueduct.
• IV thiamine before glucose; correct magnesium; treat on suspicion.
• Untreated: 10–20% mortality, and about 80% of survivors develop Korsakoff syndrome.
• Risk groups: alcohol use disorder, hyperemesis gravidarum, bariatric surgery, starvation and refeeding, anorexia nervosa, cancer, AIDS, dialysis.
• Recovery: eye signs improve within a day; memory often doesn't fully return.

Sources

• Wernicke Encephalopathy — Merck Manual Professional Edition
• Korsakoff Psychosis — Merck Manual Professional Edition
• Thiamine Deficiency — Merck Manual Professional Edition
• Alcohol Toxicity and Withdrawal — Merck Manual Professional Edition
• Portosystemic Encephalopathy — Merck Manual Professional Edition
• Wernicke-Korsakoff Syndrome — National Institute on Alcohol Abuse and Alcoholism (NIAAA)
• Thiamin — Linus Pauling Institute Micronutrient Information Center, Oregon State University