Wernicke‘s encephalopathy is an acute, reversible neurological disorder that results from thiamine (vitamin B1) deficiency, and manifesting in neurocognitive dysfunction. It is considered an emergency, because it can subsequently cause the chronic and irreversible Korsakoff syndrome/psychosis.
It is usually attributed to alcohol abuse. It has a higher prevalence in those with a history of alcohol dependence, in those with AIDS, and in bone marrow transplant recipients. The prevalence is higher in males, with a male-to-female ratio of 1.7:1, often attributed to the higher incidence of alcoholism in men.
Pathophysiology
Thiamine is involved in carbohydrate, fat, amino acid, glucose, and alcohol metabolism and is particularly important in the function of central and peripheral nerve cells and the myocardium. It is a water-soluble vitamin and is stored in the liver for a short while only (half-life of 9-18 days) so regularly dietary intake is necessary.
Sources of thiamine in the diet include:
- Whole grains
- Fortified cereals
- Legumes
- Nuts and seeds
- Pork and organ meats
- Yeast
- Some vegetables - such as peas
Thiamine is used by the enzyme thiamine pyrophosphate. This enzyme is a co-enzyme used in carbohydrate metabolism. Therefore deficiencies can lead to decreased carbohydrate metabolism (and subsequently less energy) The brain and nerve cells require a lot of energy and as such the decrease in carbohydrate metabolism that occurs with thiamine deficiency leads to cellular damage. Myocardial cells other myocytes can use long-chain fatty acids for energy (through beta-oxidation), therefore they are not damaged in thiamine deficiency (unless there is concomitant long-chain fatty acid deficiency).
Thiamine deficiency does not only cause Wernicke’s encephalopathy, but may also cause:
- Dry beriberi - distal peripheral polyneuropathy characterised by paraesthesia, reduced knee jerks and other tendon reflexes, and progressive severe weakness with muscle wasting. Secondary to chronic deficiency.
- Wet beriberi - high-output cardiac failure with peripheral vasodilation, peripheral oedema, and orthopnoea. Secondary to acute or chronic deficiency.
- Shoshin beriberi - rapid onset of low-output cardiac failure with lactic acidosis and peripheral cyanosis. Secondary to acute or chronic deficiency.
⚠️ Risk factors
- Alcohol abuse - due to impaired intestinal thiamine absoprtion
- Bariatric surgery - as a result of reduced dietary intake and altered digestion and absorption after surgery
- Hyperemesis gravidarum - as this is a state of persistent vomiting with higher metabolic demands which are not being met
- Malnutrition
😷 Presentation
Wernicke’s encephalopathy has the following classic triad (the individual may show one or two of these, not necessarily all 3):
- Ataxia - wide-based, small steps [unsteady and uncoordinated movements]
- Confusion - disorientation and difficulty with attention
- Ocular abnormalities - this can include gaze-evoked nystagmus, spontaneous upbeat nystagmus, and horizontal or vertical ophthalmoplegia.
🔍 Investigations
- 🥇 Therapeutic trial of parenteral thiamine
- Bloods (to look for concomitant problems):
- FBC
- Renal function tests
- LFT's
- Finger-prick glucose
- U&E's
- Serum ammonia - a metabolic encephalopathy due to hyperammonaemia can easily mimic or be confused with Wernicke's encephalopathy.
- Blood thiamine levels
- Blood alcohol level
- Serum magnesium - because Mg is needed for thiamine function, so low levels may impair the therapeutic benefit of thiamine
- 🏆 To confirm a diagnosis of Wernicke’s encephalopathy:
- Patient's history
- Neurological examination (including cranial nerves and eye examination) - to assess the characteristic triad of symptoms
- MRI head - may show characteristic changes in specific brain regions, such as the mammillary bodies and periaqueductal area.
- Blood tests - may show low thiamine levels or other abnormalities depending on the underlying cause
🧰 Management
Management of Wernicke's encephalopathy primarily involves replacement of thiamine.
- 🏆 High-dose IV thiamine - commonly given as Pabrinex IV. Pabrinex is a combination of B1, B2 B3 B6, and C vitamins. Thiamine (vitamin B1) can be given orally following pabrinex administration
🚨 If left untreated, the condition can progress to Korsakoff's syndrome, which affects the mammillary bodies, leading to irreversible deficits in anterograde and retrograde memory (anterograde and retrograde amnesia). Wernicke-Korsakoff syndrome is both Wernicke’s encephalopathy and Korsakoff’s syndrome combined.
- Wernicke’s COAT:
- Confusion
- Ophthalmoplegia
- Ataxia
- Thiamine deficiency
- Korsakoff’s RACK:
- Retrograde amnesia
- Anterograde amnesia
- Confabulation
- Korsakoff’s psychosis
