MINI-SYMPOSIUM: NEUROPATHOLOGY
Alcohol and the nervous system

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Summary

Alcohol is a substance that impacts the social, psychological, medical, economic and religious spheres of our existence. It is part of every society. Alcohol in moderation can be beneficial. Alcohol abuse mediates its effects both on the developing and the developed brain, directly or indirectly, and has acute and chronic complications. Damage to the developing brain can result from alcohol consumption in pregnancy. Misuse of alcohol in adults can affect both the central and the peripheral nervous system. Direct effects arise due to the toxic and intoxicating effects of alcohol. Nutritional deficiencies are thought to mediate most of the indirect effects of alcohol, as patients with alcohol dependence tend to eat less and derive most of their caloric intake from the alcoholic beverages they consume. Alcohol-related disease places a burden on our health-care systems. In this review, we examine the pathological effects of alcohol on the nervous system.

Introduction

Alcohol in the form of ethanol is probably the commonest ‘recreational drug’ in Western societies. It is estimated that approximately 90% of people consume it at some stage and 30% develop alcohol-related disorders.1 Alcohol consumption in moderation can have beneficial effects.2, 3 Problems arise when it is abused. Alcohol dependence (alcoholism) is observed in some 10% of men and 3–5% of women. An additional 5–10% of each sex develop persistent but less intense problems that are diagnosed as alcohol abuse.1 Patterns of drinking are changing worldwide with more females and young people drinking excessively, and up to 10% of females continuing to drink during pregnancy.4 Adolescents are vulnerable to the memory impairing effects of alcohol but less sensitive to its sedative and motor-impairing effects, which may partially explain the high preponderance of young adults in fatal accidents.5 Although it is known that alcohol is implicated in a high proportion of fatal accidents and suicides, interpreting blood alcohol concentrations (BACs) in autopsy samples can be difficult.6

This paper will discuss the effects of alcohol on the developing nervous system. The acute and chronic, direct and indirect effects of excess alcohol consumption on the adult nervous system will then be addressed.

Section snippets

Alcohol and the developing nervous system

Foetal alcohol syndrome (FAS) (growth retardation, distinct facial appearance and central nervous system (CNS) dysfunction) is not the only outcome resulting from prenatal alcohol exposure. The term foetal alcohol spectrum disorder (FASD) was adopted as an umbrella term to describe the range of effects that may arise in an individual exposed to alcohol in utero.7 The amount of alcohol reaching the developing embryo is a major factor, determined in part, by dose and pattern of alcohol exposure.

Memory

Blackouts are episodes of amnesia thought to be due to a rapid rise in BAC. The mechanism is thought to be a block in the transfer of information from short-term memory to long-term storage. Potentiating factors include drugs such as benzodiazepines and marijuana. During these episodes individuals are able to function appropriately, carrying out conversations and other activities. The memory impairment is anterograde. There are two types. En bloc blackouts are those where individuals cannot

Conclusion

Ethanol has many direct and indirect effects on the nervous system. In moderation it can have beneficial effects. There appears to be no safe limit for alcohol consumption in pregnancy. In adults acute intoxication with sufficiently large quantities of alcohol can lead to cardiorespiratory depression and death. However, there is considerable variation in this response, as tolerance occurs with continuous exposure.

Practice points

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    Alcohol may affect the developing nervous system

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    Its effects on the developed

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