Academic journal article Alcohol Health & Research World

The Role of Liver Disease in Alcohol-Induced Cognitive Defects

Academic journal article Alcohol Health & Research World

The Role of Liver Disease in Alcohol-Induced Cognitive Defects

Article excerpt

Cognitive dysfunction is common among alcoholics; up to 75 percent of detoxified long-term alcohol-dependent patients show symptoms of cognitive impairment (Arria et al. 1990). Several factors have been proposed to contribute to alcohol-induced cognitive dysfunction. They include direct toxic effects of alcohol on nerve cells; compromised nutritional status (particularly thiamine

i.e., vitamin B

deficiency; see article by Langlais, pp. 113-121); and alcohol-induced damage to other organs, such as the liver.

Chronic alcohol abuse is the most important cause of liver disease in the United States. For example, about two-thirds of patients suffering from medical consequences of chronic liver disease have co-occurring diagnoses of alcohol abuse or dependence (Dufour and Caces 1993). A growing body of evidence suggests that alcohol-induced liver disease also plays an important role in precipitating the cognitive impairment encountered in alcohol-dependent patients and compounds the alcohol's neurotoxic effects. For example, alcoholics with cirrhosis exhibit greater impairment in writing speed and reaction times than do alcoholics without liver disease (Gilberstadt et al. 1980). Similarly, when brain functions of alcoholics with and without cirrhosis were studied by such methods as measuring the blood flow through the brain or performing an electroencephalogram (EEG), patients with cirrhosis showed greater impairment than did patients without liver disease (Tarter et al. 1993). Finally, among alcoholic patients with various stages of cirrhosis, their performance on neuropsychological tests correlated with the severity of their liver disease (Pomier Layrargues et al. 1991).

This article focuses on the symptoms and causes of the most prevalent liver disease-associated brain dysfunction, portal-systemic encephalopathy (PSE). Although PSE also can be the consequence of nonalcoholic liver disease (i.e., cirrhosis), at least 50 percent of PSE cases result from alcoholic cirrhosis. Therefore, unless specifically mentioned otherwise, terms such as "liver damage" or "cirrhosis" refer to both the alcoholic and nonalcoholic disorder. In alcohol-dependent PSE patients, however, it is assumed PSE results from alcohol-induced liver damage.

This article describes how liver dysfunction may lead to PSE by causing alterations in several pathways of communication between nerve cells. The article also addresses the effectiveness of one potential treatment--liver transplantation--for liver disease and the PSE resulting from it.

PORTAL-SYSTEMIC ENCEPHALOPATHY

PSE, which is a common complication of cirrhosis (Butterworth 1994a), develops slowly and progresses through several distinct clinical stages that are characterized by specific cognitive and neuromuscular symptoms (table 1).(Table 1 omitted) The earliest symptoms include alterations of sleep patterns, reduced attention span, anxiety, depression, and muscle incoordination. As the condition progresses, additional symptoms appear, such as personality changes, memory loss, asterixis,(1) confusion, stupor, and muscle rigidity. The disorder's final stage is characterized by hepatic coma. The progression of PSE, which can happen rapidly, can be brought on by various factors, such as deterioration of the patient's general health, gastrointestinal bleeding, infections, kidney failure, or use of sedative drugs (Arria et al. 1990).

As a result of the wide spectrum of psychiatric and neuromuscular symptoms encountered in alcohol-dependent patients with PSE, physicians often fail to diagnose the disorder correctly or even to recognize alcohol's contribution to the development of the disorder. In the past, misdiagnoses have included depression, schizophrenia, mild forms of mania, and Parkinson's disease (Tarter et al. 1986). The PSE diagnosis is complicated further by the fact that not all patients with PSE have obvious signs of liver disease and abnormal liver test results. …

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