neurological disorder characterized by severe amnesia (memory loss). Many cases result from severe chronic alcoholism, while others are due to a variety of brain disorders, severe head injury, or a thiamine deficiency. Patients with Korsakoff syndrome typically are unable to remember events in the recent or even the immediate past, and some can store information for only a few seconds before they forget it. The patient may also have forgotten a much longer time period, extending back for as many as 20 years. Another feature that is sometimes present is confabulation; i.e., the patient recounts detailed and convincing memories of events that never happened. Korsakoff syndrome is often a transient manifestation of some other brain disorder, but some cases are chronic. In chronic alcoholism, Korsakoff syndrome may occur in combination with Wernicke disease, which results from a deficiency of thiamine (thiamin) and is characterized by damage to nerves in both the central and peripheral nervous system.