Toxins and metabolic abnormalities should be considered in all cases of dementia, but especially in the elderly, who have a higher prevalence of systemic illness and medication use. The list of toxic/metabolic causes of dementia is extensive (see Table 8.2). Many of these conditions produce an acute confusional state more often than a dementia. Nonetheless, they are not infrequently identified in epidemiological studies of dementia. In 200 elderly patients with symptoms for three or more months, medications (9.5%) and hypothyroidism (3%) were the leading toxic/metabolic causes of dementia (Larson, Reifler, Suni, Canfield, & Chinn, 1986). Features that favored a toxic/metabolic cause were a higher number of prescription medications and a shorter duration and lesser severity of dementia. This chapter reviews the toxic/metabolic dementias associated with alcoholism, thyroid disease, and
Table 8.2 Toxic/Metabolic Causes of Dementia
Exogenous Toxins Alcohol Medications Brain radiation Organic solvents Heavy metals Carbon monoxide Metabolic Abnormalities Endocrine imbalance Pulmonary insufficiency Cardiac failure Hematological disorders Renal dysfunction Hepatic failure Electrolyte derangement Nutritional deficiency vitamin B12 deficiency. Details of other toxic/metabolic causes of dementia may be found in a review by Feldmann and Plum (1993).
Neuropsychological impairment may be detected in nearly half of individuals who drink excessive alcohol daily. Women and the elderly are particularly susceptible (Cummings & Benson, 1983). The prevalence of overt dementia is lower but may approach 25% in elderly alcoholics (Finlayson, Hurt, Davis, & Morse, 1988). Pellagra as a cause of dementia in alcoholics has diminished greatly since the institution of grain products fortified with niacin. Degeneration of the corpus callosum, Marchiafava-Bignami disease, is a rare complication of chronic alcohol consumption. It was first described in red wine-drinking Italian men, but has since been reported with many other forms of alcohol and in multiple locations worldwide. Hy-pothyroidism and vitamin B12 deficiency are both common in the elderly, but B12 deficiency is much rarer as a cause of dementia.
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