wernicke's encephalopathy

Meaning: Thiamine is a cofactor for enzymes of glucose metabolism, so a deficiency starves neurons of energy. Damage falls on diencephalon structures such as the thalamus and mammillary bodies. Heavy, long-term alcohol use is the classic cause because of poor diet and poor absorption of the vitamin. The acute stage features confusion, poor coordination (ataxia) and eye-movement abnormalities, though not every patient shows all three. If the deficiency persists, many patients develop Korsakoff syndrome, and the two together are called Wernicke-Korsakoff syndrome.

On the MCAT: A passage describes a person with a long history of alcohol use who cannot form new declarative memories (anterograde amnesia), may also lose some older memories, and fills gaps with invented but sincere stories (confabulation). You name the condition as Korsakoff syndrome and link it to thiamine deficiency. Questions may then ask which memory type is impaired: explicit (declarative) memory suffers, while implicit memory such as procedural skill is relatively spared.

Common confusion: Do not mix this with Wernicke's area or Wernicke's aphasia. Wernicke's area is in the left temporal lobe and supports language comprehension. Damage to it gives fluent but meaningless speech with poor understanding. Wernicke's encephalopathy is a nutritional brain injury, and its lasting memory stage is named for Korsakoff, not Wernicke.