Wernicke encephalopathy vs Korsakoff syndrome
Two stages of the same disease — thiamine (B1) deficiency damaging the medial diencephalon. Wernicke is the acute, reversible phase. Korsakoff is the chronic, often irreversible one.
Mechanism
Both result from thiamine (vitamin B1) deficiency, most often in chronic alcohol use disorder (alcohol impairs thiamine absorption AND alcoholics are nutritionally depleted). Lesions are in the mammillary bodies, dorsomedial thalamus, and periaqueductal gray:
- Wernicke encephalopathy — the acute syndrome. Classic triad: confusion (encephalopathy), ataxia (gait, truncal), ophthalmoplegia/nystagmus (especially lateral rectus / abducens; horizontal nystagmus). Reversible with prompt IV thiamine. The complete triad is present in only ~10% of cases — treat empirically on suspicion.
- Korsakoff syndrome — the chronic, often permanent sequela of untreated Wernicke. Defining feature: anterograde amnesia (cannot form new memories) plus retrograde amnesia, with confabulation (fabricating plausible-sounding memories to fill gaps, often without awareness). Personality may be apathetic.
Critical clinical rule: give thiamine BEFORE glucose in any alcoholic with altered mental status. Glucose loading without thiamine accelerates thiamine consumption and can precipitate Wernicke.
Differentiator Table
| Wernicke encephalopathy | Korsakoff syndrome | |
| Tempo | Acute, days | Chronic, persistent |
| Hallmark | Triad: confusion + ataxia + ophthalmoplegia/nystagmus | Anterograde amnesia + confabulation |
| Memory | Globally impaired (delirium) | Specifically anterograde — can't make new memories |
| Reversibility | Reversible with thiamine if treated promptly | Often irreversible; ~20% recover with prolonged thiamine |
| Pathology — site | Mammillary bodies, dorsomedial thalamus, periaqueductal gray | Same regions, with chronic damage |
| Imaging | Mammillary body enhancement / atrophy | Mammillary body atrophy |
| Treatment | IV thiamine FIRST, then glucose | Thiamine + supportive cognitive rehab |
The Pivot
Two questions:
- Triad in an alcoholic (or post-bariatric, or hyperemesis)? → Wernicke. Treat now.
- Apathetic patient with anterograde amnesia who tells confident, fabricated stories? → Korsakoff.
The trap: NBME often asks about order of administration. The answer is always thiamine before glucose in suspected Wernicke. Never reverse.
NBME-Style Stem
A 54-year-old man with a long history of alcohol use disorder is brought to the ED confused and ataxic. On examination he has nystagmus on lateral gaze and weakness of right lateral gaze. Glucose is 78 mg/dL. Which of the following is the most appropriate next step in management?