Basic Neurosciences · Paper A
Wernicke-Korsakoff syndrome
Wernicke-Korsakoff syndromeA chronic memory disorder, usually from thiamine deficiency, marked by severe short-term memory loss and confabulation.Read more → is brain damage from a lack of thiamine (vitamin B1), most often in alcohol dependence. It has an acute, reversible phase (Wernicke's) and a chronic, often permanent phase (Korsakoff's). A patient with alcohol dependence who develops confusion and unsteady gait after a period of poor eating shows this pattern. Treating with thiamine immediately, before waiting for the full classic triad to appear, is essential.
Wernicke's encephalopathyAn acute brain condition from thiamine deficiency causing confusion, ataxia, and abnormal eye movements.Read more → is the acute, treatable phase. Its classic triad is confusion, ophthalmoplegiaWeakness or paralysis of the muscles that move the eyes.Read more → (weak eye-movement muscles, especially causing nystagmusRepeated, involuntary back-and-forth eye movements.Read more →, or jerky eye movements) and ataxiaLoss of full control of body movements, causing an unsteady, uncoordinated gait or actions.Read more → (an unsteady, clumsy gait from loss of coordination). All three together are uncommon, so treat on suspicion. Korsakoff's syndrome is the chronic memory disorder: severe anterograde amnesia (an inability to form new memories) with relative preservation of other thinking, plus confabulationFilling a gap in memory with a made-up answer the person genuinely believes is true, not a deliberate lie.Read more → (filling memory gaps with invented details). e.g. a patient who only has confusion, without eye signs or ataxia: still treat for Wernicke's, since the full triad is uncommon and waiting for all three risks permanent Korsakoff amnesia. The memory system most affected in Korsakoff's syndrome is episodic memory (memory for personal experiences and events). Procedural memory (skills and habits), working memory (holding and manipulating information over the short term) and previously-acquired semantic knowledge (facts and general knowledge) are all relatively preserved. That is why a patient with Korsakoff's can hold a fluent, coherent conversation despite being unable to form new memories. At the biochemical level, thiamine is a cofactor for transketolase, an enzyme central to the pentose phosphate pathway; when thiamine is deficient, it is transketolase dysfunction that drives the neuronal damage to the mammillary bodies and other diencephalic structures. Korsakoff's syndrome is not a tauopathy (it is not caused by abnormal tau protein deposition), which distinguishes it from Alzheimer's disease and other tau-related dementias. Roughly 80% of patients who survive an episode of Wernicke's encephalopathy go on to develop Korsakoff's syndrome, which is why prompt thiamine at the acute stage matters so much for the longer-term outcome.
This is one of the few psychiatric-adjacent emergencies where a single wrong ordering decision, giving glucose before thiamine, can permanently damage a patient's memory. Understanding the sequence, the triad, and the underlying deficiency is essential both for exams and for real emergency-department safety.
Wernicke- is brain damage caused by a lack of thiamine (vitamin B1), most often seen in people with alcohol dependence, though it can occur in anyone who is severely malnourished. It has two phases: an acute, reversible phase called , and a chronic, often permanent phase called Korsakoff's syndrome (also called Korsakoff's psychosis).
A dangerous assumption is that the full triad of Wernicke's (confusion, eye-movement problems, and unsteady gait) must all be present before treating. It must not be. All three signs occurring together is uncommon in practice, so clinicians treat on suspicion whenever even one element appears in an at-risk patient, rather than waiting for the complete picture and risking permanent damage.
Thiamine is a cofactor (a helper molecule) that several brain enzymes need to produce energy. Without it, energy-hungry brain regions are damaged first, particularly the mammillary bodies (small structures involved in memory) and nearby midline structures. Alcohol reduces thiamine absorption, storage and use all at once, which is why chronic alcohol dependence combined with poor eating is the classic setup for this syndrome, though any cause of severe malnutrition can produce the same picture.
is the acute, treatable phase, and its classic triad is confusion, (weak eye-movement muscles, especially producing , or jerky eye movements) and (an unsteady, clumsy gait from loss of coordination). Korsakoff's syndrome is the chronic memory disorder that can follow an inadequately or untreated Wernicke's episode. Its hallmark is severe anterograde amnesia (an inability to form new memories from the point of onset onward), with other thinking skills relatively preserved, plus (unconsciously filling memory gaps with invented details, not deliberate lying). Established Korsakoff amnesia is often permanent, unlike the reversible confusion of Wernicke's.
Several conditions mimic parts of this picture and need to be told apart. Delirium tremens (a severe alcohol-withdrawal state with autonomic hyperactivity (tremor, sweating, tachycardia) plus , typically 48-72 hours after the last drink) shares confusion with Wernicke's but has a different time course and a prominent autonomic component that Wernicke's lacks. Hepatic (confusion from liver failure, with a flapping tremor called asterixis and a raised blood ammonia) also overlaps on confusion but has a different biochemical driver and needs a different treatment, lactulose, not thiamine. Simple alcohol intoxication causes and confusion too, but resolves as blood alcohol falls, whereas Wernicke's does not improve until thiamine is given. When any of these is possible, treat empirically for Wernicke's anyway, because untreated thiamine deficiency is the one that causes permanent harm.
Diagnosis of is mainly clinical, based on the triad, or even a single element of it, plus the at-risk history, since waiting for a confirmatory blood thiamine investigation would dangerously delay treatment. Brain imaging (typically MRI) may show characteristic changes around the mammillary bodies in some cases, but a normal scan does not exclude the diagnosis, and imaging should never delay thiamine administration. Screening at-risk patients (anyone with alcohol dependence, severe vomiting in pregnancy, or a history of weight-loss surgery) for signs of deficiency is a recommended part of routine assessment.
Give thiamine before any glucose. Giving glucose first can precipitate or worsen in a thiamine-deficient patient, because glucose metabolism consumes the little thiamine that remains. This is a genuine emergency-department management rule, reflected in BNF dosing guidance and the Maudsley Prescribing Guidelines, and NICE alcohol-related guidance similarly emphasises prompt parenteral (injected) thiamine for anyone with suspected Wernicke's, rather than oral replacement, because oral absorption is unreliable in this population. Once Korsakoff's syndrome is established, ongoing management is largely supportive: structured routines, memory aids and, where relevant, continued abstinence support, since the amnesia itself rarely reverses with further treatment. Prevention is far more effective than any later management strategy, which is why thiamine supplementation is routinely offered alongside alcohol detoxification.
A frequent exam trap presents a patient with only confusion, without eye signs or , implying that Wernicke's can be excluded. It cannot: still treat for Wernicke's, since the full triad is uncommon, and waiting for all three signs risks permanent Korsakoff amnesia. Suppose a malnourished patient arrives in A&E and is given IV dextrose before thiamine, simply because glucose felt like the routine, urgent step: that seemingly ordinary sequencing choice can precipitate florid in someone who was previously only borderline thiamine-deficient, which is exactly why the thiamine-first rule is drilled into emergency teams.
Give thiamine before any glucose in a suspected Wernicke's patient; Wernicke's can reverse with prompt treatment, but established Korsakoff amnesia often does not.