Wernicke's encephalopathy presents with an acute or subacute confusional state, together with oculomotor disturbance and ataxia.
The tendency to confabulate was noted, as was the link with alcohol abuse, but it was also reported with typhoid fever and prolonged vomiting. Six years earlier, Wernicke had described an acute illness of ataxia, ophthalmoplegia, polyneuropathy, and a confusional state. It was later observed that these syndromes often occurred sequentially in the same patient. The majority of cases are now associated with alcohol abuse, and thiamine deficiency plays a key role in Wernicke's encephalopathy.
The confusional state involves inattention and disorientation but can progress to drowsiness and even to coma and death if the underlying thiamine deficiency is not recognized and treated. The examination may reveal nystagmus, VIth nerve palsies, conjugate gaze palsies, and ataxia. Criteria reflecting the classic triad of encephalopathy, oculomotor disturbance, and ataxia have been developed (Caine et al. 1997). The occurrence of any two of the following—dietary deficiency, oculomotor palsies, cerebellar dysfunction, and altered mental state—can provide high diagnostic accuracy.
Korsakoff's syndrome emerges as Wernicke's encephalopathy resolves, and the confusional state clears to reveal a profound amnesia with both an inability to recall recent events and to learn new facts (Kopelman 1995).
The key component is the impairment of memory out of proportion to other cognitive domains. The deficit relates to event or episodic memory with sparing of semantic memory, and implicit learning can be demonstrated. Early lifetime memories are preserved, with a steeper temporal gradient than is typically seen in Alzheimer's disease (Kopelman 1995). Classically, patients also confabulate and will easily confuse the temporal sequence of memories that are recalled; this is believed to relate to additional frontal damage and, indeed, many patients lack insight and initiative, indicative of a frontal syndrome. However, more widespread cognitive deficits may be seen, and a clinical picture which merges with ‘alcohol dementia’ (Cutting 1978).
Thiamine deficiency is believed to underlie the pathogenesis of the disorder, and explains its occurrence in other disorders such as prolonged vomiting, nutritional deficiency, and hyperemesis gravidarum. In patients who abuse alcohol, there is considerable variability in susceptibility to Wernicke–Korsakoff syndrome, suggesting not only subtle differences in diet but also potential genetic factors.
Bilateral haemorrhagic lesions in the areas of the third and fourth ventricle and aqueduct are characteristic of Wernicke's encephalopathy, and the diencephalic lesions are critical to the emergent amnesia of Korsakoff's syndrome.
The original proposal that damage to the dorsal medial nucleus of the thalamus was the minimal lesion (Victor et al. 1989) has been considered too specific, and anterior and medial thalamic and mammillary body involvement are also implicated. Shrinkage of the mammillary bodies is also seen in non-Korsakoff alcoholic cognitive impairment.
The key to the treatment is to make the diagnosis, which should be considered in all patients presenting acutely with unexplained cognitive impairment or coma. Treatment is with intravenous thiamine, at least 100 mg daily. In the acute situation it is important to give thiamine before intravenous glucose (Heye et al. 1994).