In the category of disorders caused by toxins, multiple syndromes of nervous system abnormalities may occur related to alcohol (ethanol) consumption, some of which are quite common. Alcohol intoxication may cause rapid diffuse dysfunction of both the cerebrum and cerebellum. The cerebellar dysfunction often causes gait ataxia and slurred speech. The parts of the cerebral cortex most often affected are involved in cognitive and emotional functions, but consciousness may also become impaired. Alcohol intoxication also raises the risk of seizures.
People who consume large amounts of alcohol daily for long periods may develop a withdrawal syndrome in the days after they stop drinking. Alcohol withdrawal may cause tremors, delirium, seizures, or autonomic abnormalities, including potentially fatal abnormal heart rhythms. In addition to these faster neurological syndromes, chronic heavy alcohol consumers may develop several slow syndromes over months to years due to degeneration of parts of the nervous system. This may include polyneuropathy, or may involve degeneration of the cerebral or cerebellar cortex that may lead to dementia or ataxia. This population is also at particularly high risk for thiamine deficiency.
The nutritional disorder thiamine deficiency may also cause fast as well as slow neurological syndromes. One of these is called Wernicke’s encephalopathy, which may develop over hours to days with thiamine deficiency. This syndrome may have delirium, abnormal eye movements, or gait ataxia. Korsakoff’s dementia is another syndrome that may occur with thiamine deficiency, usually over months to years. This type of dementia often includes difficulty forming new memories as a particularly prominent feature. Many patients will have an overlapping syndrome with features of both. Wernicke’s encephalopathy may be reversible if treated early, but Korsakoff’s dementia tends to be irreversible.