Wernicke's encephalopathy

Overview

•Acute, potentially reversible neuropsychiatric emergency caused by thiamine (vitamin B1) deficiency

•Classically associated with chronic alcohol misuse - but any cause of severe nutritional deficiency can trigger it (post-bariatric surgery, hyperemesis gravidarum, prolonged vomiting/malnutrition)

•Thiamine is an essential cofactor for aerobic carbohydrate metabolism - deficiency causes intracellular energy failure and selective neuronal injury

⚠️

Giving IV glucose to a thiamine-depleted patient accelerates thiamine consumption and can precipitate or worsen Wernicke's. Always give thiamine before or simultaneously with glucose in any at-risk patient.

Presentation

•Classic triad: confusion, ophthalmoplegia/nystagmus, ataxia - but complete triad present in fewer than 20% of cases

•Ocular signs - nystagmus (most common), bilateral lateral rectus palsy (horizontal diplopia), conjugate gaze palsy

•Ataxia - broad-based, unsteady cerebellar gait

•Confusion - ranges from disorientation/apathy to delirium

•Peripheral neuropathy - reduced reflexes, distal weakness (common associated finding)

🧠

Wernicke's COAT: Confusion, Ophthalmoplegia/nystagmus, Ataxia, Thiamine deficiency. Korsakoff's RACK (irreversible sequela): Retrograde amnesia, Anterograde amnesia (dominant), Confabulation, Korsakoff's psychosis.

Investigations

🎯

Diagnosis is primarily clinical. Do not delay treatment to await investigation results - if Wernicke's is suspected, give Pabrinex immediately.

🥇 First-line

•thiamine level, FBC (macrocytosis), U&Es, LFTs, glucose, magnesium (hypomagnesaemia impairs thiamine utilisation), CT head (exclude haemorrhage/SOL - poor sensitivity for Wernicke's itself)

🏆 Gold standard

•MRI head - T2/FLAIR hyperintensities in mammillary bodies, periaqueductal grey, and medial thalami; note: normal MRI does not exclude Wernicke's

Management

🥇 First-line

•Pabrinex (IV vitamins B and C, high-dose) - 2 pairs of ampoules IV three times daily for minimum 3-5 days; slow IV infusion over 30 minutes due to anaphylaxis risk - resuscitation facilities must be available

•Pabrinex contains B1 (thiamine), B2 (riboflavin), B3 (nicotinamide), B6 (pyridoxine), and C (ascorbic acid) - thiamine (B1) is the key active component

🥈 Second-line

•oral thiamine (e.g. 100 mg three times daily) once improving and tolerating oral intake; correct hypomagnesaemia if present

🥉 Third-line

•chlordiazepoxide (tapering regimen) for concurrent alcohol withdrawal - this is a separate clinical decision, not a substitute for thiamine replacement

🚨

Never give IV glucose to a malnourished/at-risk patient without first giving thiamine. Glucose load → rapid aerobic metabolism → accelerated thiamine depletion → Wernicke's precipitated or worsened. Thiamine first, always.

Complications and Prognosis

•Korsakoff's syndrome - irreversible sequela; profound anterograde amnesia, retrograde amnesia, confabulation; results from irreversible neuronal loss in mammillary bodies and medial thalami

•~80% of patients who develop Korsakoff's following untreated Wernicke's will have persistent, irreversible memory impairment

•With prompt treatment: ocular signs improve within hours to days (most responsive); ataxia over days to weeks; confusion more slowly and may be incomplete

💡

Treat on suspicion, not confirmation - the clinical threshold must be low. The complete triad is absent in >80% of cases at diagnosis.