Wernicke's encephalopathy

Wernicke encephalopathy is a syndrome characterised by ataxia, ophthalmoplegia, nystagmus, confusion, and impairment of short-term memory. It is caused by lesions in the medial thalamic nuclei, mammillary bodies, periaqueductal and periventricular brainstem nuclei, and superior cerebellar vermis, often resulting from inadequate intake or absorption of thiamine (vitamin B1), especially in conjunction with carbohydrate ingestion. It is most commonly correlated with prolonged alcohol consumption resulting in thiamine deficiency. Alcoholics are therefore particularly at risk, but it may also occur with thiamine deficiency states arising from other causes, particularly in patients with such gastric disorders as carcinoma, chronic gastritis, Crohn's disease, and repetitive vomiting, particularly after bariatric surgery.

Presentation
Wernicke's encephalopathy begins abruptly, usually with eye movement disorders (nystagmus, gaze palsies, and ophthalmoplegia, especially of the lateral rectus muscles), gait ataxia, confusion, confabulation, and short-term memory loss.

The classic triad of the syndrome is confusion, ophthalmoplegia (eye paralysis), and ataxia (loss of coordination), though these are only seen in combination in 10% of cases. Untreated it may progress to Korsakoff's psychosis, coma and death. The pathological changes seen in Wernicke's encephalopathy are concentrated in the mammillary bodies, cranial nerve nuclei III, IV, VI and VIII, the thalamus, hypothalamus, periaqueductal grey, cerebellar vermis, and the dorsal nucleus of the vagus nerve. The ataxia and ophthalmoparesis are related to lesions in the oculomotor, trochlear, abducens, and vestibular (IIIrd, IVth, VIth, and VIIIth cranial) nerve nuclei.

Despite its name, Wernicke's encephalopathy is not related to Wernicke's area, a region of the brain associated with speech and language interpretation. (See Wernicke's aphasia.)  Rather, both are named for the 19th century neurologist Carl Wernicke.

Cause
The neuropathy of Wernicke's encephalopathy causes neuron death due to the effects of thiamine deficiency upon astrocytes. This causes alterations in their glutamate uptake, through changes in the levels of the astrocytic glutamate transporters EAAT1 and EAAT2 creating excitotoxicity. Other changes include those to the GABA transporter subtype GAT-3, GFAP, glutamine synthetase, the water channel protein Aquaporin 4. These create lactic acidosis, brain edema, oxidative stress, inflammation, and white matter damage.

Treatment
Treatment begins with intravenous or intramuscular injection of thiamine, followed by assessment of central nervous system and metabolic conditions. In the presence of sub-clinical thiamine deficiency, a large dose of sugar (especially glucose) can precipitate the onset of overt encephalopathy; therefore, correcting hypoglycemia should not be attempted before thiamine replenishment. Rehydration to restore blood volume should follow, as needed.

Prognosis depends on severity. When treated early, recovery is normally rapid and complete. Established Wernicke's encephalopathy, by contrast, can have serious long-term consequences, with patients requiring permanent in-patient care.