Korsakoff's syndrome

Meaning: Korsakoff's syndrome is an amnestic disorder caused by thiamine deficiency. The deficiency damages the diencephalon, including the mammillary bodies and thalamus, which belong to the circuit that stores new explicit memories. It is most often tied to chronic alcohol use, because of poor nutrition and impaired thiamine absorption. Its main features are: 1. Anterograde amnesia: trouble forming new explicit memories. 2. Retrograde amnesia: loss of older memories, to a varying degree. 3. Confabulation: filling memory gaps with invented details that the patient sincerely believes. Implicit memory, such as procedural skills, and general intelligence are relatively preserved.

On the MCAT: A passage describes a patient with a long history of heavy drinking who cannot recall what happened this morning, tells detailed but false stories about it, and can still perform a practiced skill. Questions ask which type of memory is impaired (explicit, not implicit), which vitamin is involved, or how the pattern differs from other memory disorders. Expect comparisons with Alzheimer's disease (progressive neurodegeneration, with early hippocampal and cortical involvement) and with hippocampal damage, where anterograde amnesia is also prominent.

Common confusion: Confabulation is not lying. The patient has no intent to deceive and believes the story. Also, do not treat Korsakoff's as purely anterograde. Retrograde loss is usually present too, though the anterograde deficit is the hallmark.