Merck Manual

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Wernicke Encephalopathy

(Wernicke's Encephalopathy)


Gerald F. O’Malley

, DO, Grand Strand Regional Medical Center;

Rika O’Malley

, MD, Albert Einstein Medical Center

Last full review/revision Jun 2020| Content last modified Jun 2020
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Wernicke encephalopathy is a brain disorder that causes confusion, eye problems, and loss of balance and results from thiamin deficiency.

Wernicke encephalopathy is caused by a severe deficiency of thiamin, a B vitamin. In people who have only a small amount of thiamin stored in the body, it may be triggered by consuming carbohydrates.

Wernicke encephalopathy often develops in people with severe alcoholism because the long-term use of excess amounts of alcohol interferes with the absorption of thiamin from the digestive tract as well as the storage of thiamin in the liver. Also, people with alcohol use disorder often do not consume an adequate diet and thus not enough thiamin. Wernicke encephalopathy may result from other conditions that cause prolonged undernutrition or vitamin deficiencies. These conditions include dialysis, severe vomiting, starvation, gastric bypass surgery, cancer, and AIDS.


Wernicke encephalopathy causes

  • Confusion

  • Drowsiness

  • Involuntary eye movements (nystagmus)

  • Partial paralysis of the eye muscles (ophthalmoplegia)

  • Loss of balance (To maintain balance, people walk with their feet far apart and take slow, short steps.)

Internal body processes may malfunction, causing tremor, agitation, a cold body temperature, a sudden and excessive decrease in blood pressure when people stand (orthostatic hypotension), and fainting.


  • A doctor's evaluation

Doctors suspect the diagnosis in people who have the characteristic symptoms and undernutrition or a thiamin deficiency, especially if they are people with alcohol use disorder.

Tests, such as blood tests to measure blood sugar levels, a complete blood cell count, liver tests, and imaging, are usually done to rule out other causes. Thiamin levels are not routinely measured.


The prognosis depends on how quickly the disorder is diagnosed and treated. Prompt treatment may correct all abnormalities. Eye problems usually improve within 24 hours of treatment. However, loss of balance and confusion may persist days to months, and memory loss may not completely resolve.

Without treatment, about 10 to 20% of people die. 80% of survivors develop Korsakoff psychosis, a disorder in which people develop memory loss, confusion, and behavioral changes. The combination is called Wernicke-Korsakoff syndrome.


  • Thiamin

  • Magnesium

  • Stopping drinking alcohol

Thiamin is given immediately by injection into a vein or muscle. It is continued daily for at least 3 to 5 days. Magnesium, which helps the body process thiamin, is also given by injection or by mouth. Fluids and multivitamins are given, and if levels of electrolytes (such as potassium) are abnormal, they are corrected. Some people may require hospitalization.

People with Wernicke encephalopathy must stop drinking alcohol. Thiamin supplements, taken by mouth, may need to be continued after the initial treatment.

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