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The pattern of brain damage Wernicke observed caused by intoxication
was later observed in victims of beriberi, an affliction with similar but even
more severe clinical signs. Oculomotor paralysis, ataxia, somnolence,
psychosis, and opistotonus (a spastic arching back of the head) death
were all part of the syndrome of beriberi preceding death. Deficiency of
thiamine (vitamin B1) was found to be the cause of beriberi, which
occurred mainly in Asian countries where rice was the dietary staple,
after refined white rice became favored over natural brown rice (Williams
1961).

Wernicke’s encephalopathy is a term used now for both thiamine
deficiency and chronic alcohol intoxication. Wernicke cited similar
pathology observed by Gayet (1875), and the term Gayet-Wernicke is
also sometimes employed. Gayet's patient was injured in a boiler
explosion, which may have caused scalding of the airway. Many toxic
substances have now been found to produce Wernicke-like patterns of
brain damage, including mercury, lead, and chemical fumes (Oyanagi et
al. 1989, Bertoni & Sprenkle 1989, Bini & Bollea 1947, Goulon et al.
1975, Squier et al. 1992, Cavanagh & Nolan 1993). The brain areas
involved are those of highest metabolic rate in the brain (Sokoloff 1981).

Thiamine is an essential cofactor for some of the mitochondrial enzymes
that catalyze aerobic metabolism. Toxic substances may directly impair
the aerobic enzymes of mitochondria; nerve gases used in chemical
warfare can disable the mitochondrial enzymes with sudden fatal
outcome. Mitochondria appear to have evolved from infectious cell
inclusions that took on a symbiotic role, and substances such as
antibiotic medications, pesticides, and herbicides damage mitochondrial
DNA causing a slower demise (Gray et al. 1999, Schapira 1998).

Korsakoff (1889) observed the signs described by Wernicke not only in
cases of chronic alcoholism, but also during the course of infections and
cancerous cachexia (or wasting which may well involve thiamine
deficiency). Korsakoff provided description of 14 cases of non-alcoholic
origin. Among these were post-partum illnesses, typhoid, tuberculosis,
tapeworm, diabetes, pneumonia, jaundice, and intestinal disorders. In
addition to early acute symptoms similar to those described by Wernicke,
Korsakoff described the long-term course leading to memory impairment.