Write a short note on Wernicke's encephalopathy.

Definition

Wernicke's encephalopathy is an acute neuropsychiatric emergency caused by thiamine (vitamin B1) deficiency, characterised classically by the triad of confusion, ophthalmoplegia and ataxia. It is reversible if treated promptly, but progresses to the irreversible Korsakoff psychosis or death if untreated. Together these constitute the Wernicke–Korsakoff syndrome.

WHY Thiamine Matters

Thiamine pyrophosphate is an essential cofactor for pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase (both in the Krebs cycle) and transketolase (pentose phosphate pathway). Deficiency impairs cerebral glucose metabolism and ATP generation, causing lactate accumulation, focal acidosis, glutamate-mediated excitotoxicity and cell death in regions of high metabolic demand.

Body stores last only 2–3 weeks, which is why deficiency develops rapidly with poor intake.

Lesions occur in periventricular structures: mammillary bodies (most characteristic), medial thalamus (dorsomedial nucleus), periaqueductal grey matter, floor of the fourth ventricle, and cerebellar vermis.

Causes

• Chronic alcohol use — the commonest cause (poor intake, impaired absorption, reduced hepatic storage, and impaired conversion to the active form).
• Hyperemesis gravidarum — an important and frequently missed cause in young women.
• Prolonged vomiting, starvation, anorexia nervosa, malnutrition.
• Post-bariatric surgery and other gastrointestinal surgery; malabsorption.
• Prolonged parenteral nutrition without thiamine supplementation; refeeding syndrome.
• Haemodialysis and peritoneal dialysis; malignancy and chemotherapy; AIDS.
• Any patient given intravenous glucose in a malnourished state — see the danger box.

Clinical Features

The classic triad — but the crucial point is that the full triad is present in only about 10–20% of cases. Treating only patients with all three components means missing most cases.

Other features: hypothermia and hypotension (hypothalamic involvement), tachycardia, peripheral neuropathy (frequently coexisting), and features of alcohol withdrawal.

Korsakoff psychosis — the chronic amnestic sequel in up to 80% of untreated survivors:

• Profound anterograde amnesia — inability to form new memories
• Retrograde amnesia with a temporal gradient
• Confabulation — filling gaps with fabricated accounts, without intent to deceive
• Relative preservation of other cognitive functions, so the patient appears superficially intact
• Lack of insight and apathy

Investigations

The diagnosis is clinical, and treatment must never be delayed for investigation.

• Serum thiamine or erythrocyte transketolase activity — confirmatory but slow and often unavailable; take the sample before giving thiamine if practical, but do not wait for the result.
• MRI brain — supportive: symmetrical T2/FLAIR hyperintensity in the mammillary bodies, medial thalami, periaqueductal grey and tectal plate, sometimes with contrast enhancement. Normal imaging does not exclude the diagnosis.
• Electrolytes, magnesium (hypomagnesaemia impairs thiamine-dependent enzymes and must be corrected, or thiamine replacement may fail), glucose, liver function, CBC, and blood alcohol.
• Exclude other causes of encephalopathy: sepsis, hepatic encephalopathy, subdural haematoma (common in alcoholics after falls), hypoglycaemia, and drug intoxication.

Management

1. Immediate high-dose PARENTERAL thiamine. Oral absorption is unreliable and inadequate — particularly in alcoholics, where absorption is impaired. Treatment is given intravenously or intramuscularly for several days, followed by oral maintenance. Prophylactic parenteral thiamine should be given to all at-risk patients, not only those with signs.

2. Correct magnesium — an essential cofactor; failure to respond to thiamine is often due to unrecognised hypomagnesaemia.

3. Give glucose only AFTER thiamine in at-risk patients.

4. Supportive care: manage alcohol withdrawal with benzodiazepines, correct fluids and electrolytes, treat infection, provide nutritional rehabilitation with multivitamins, and ensure thromboprophylaxis and pressure care.

5. Long-term: alcohol cessation with structured support, ongoing thiamine and vitamin supplementation, and cognitive rehabilitation with supervised or institutional care for established Korsakoff syndrome, where recovery is limited.

Response to treatment: ocular signs begin to improve within hours to days and are the most reversible; ataxia improves over days to weeks and may leave a residual gait disturbance; the confusional state clears over days to weeks, but memory impairment recovers least and often not at all.