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Imaging and Alcoholism: A Window on the Brain
The processes that initiate and maintain alcoholism are regulated by interactions among nerve cells (i.e., neurons) in the brain. These mechanisms interact with emotional, thinking, and social factors to determine an individual’s response to alcohol consumption.
Imaging techniques allow scientists to study the link between brain and behavior with minimal risk to the patient. Using imaging, scientists can watch the brain in action as a person performs intellectual tasks, reacts to the environment, or experiences emotions. Data obtained before, during, and after a person has consumed alcohol can be compared and analyzed. Imaging offers the promise of integrating biomedical, psychosocial, and behavioral aspects of alcoholism, leading to improved prevention and treatment. Alcohol’s Effects on Brain Structure and Function
Results of autopsy studies show that patients with a history of chronic alcohol consumption have smaller, lighter, more shrunken brains than nonalcoholic adults of the same age and gender.
This finding has been repeatedly confirmed in living alcoholics using structural imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI). Structural imaging reveals a consistent association between heavy drinking and physical brain damage, even in the absence of medical conditions previously considered to be clinical indicators of severe alcoholism (e.g., chronic liver disease or alcohol-induced dementia).
Imaging reveals shrinkage to be more extensive in the folded outer layer (i.e., cortex) of the frontal lobe, which is believed to be the seat of higher intellectual functions. In men, vulnerability to frontal lobe shrinkage increases with age. Current studies will determine if the same effect occurs in women. Repeated imaging of a group of alcoholics who continued drinking over a 5-year period showed progressive brain shrinkage that significantly exceeded normal age-related shrinkage. The rate of frontal cortex shrinkage in this study correlated approximately with the amount of alcohol consumed.
Shrinkage also occurs in deeper brain regions, including brain structures associated with memory, as well as in the cerebellum, which helps regulate coordination and balance. Limited research suggests that women may be more susceptible than men to alcohol-related brain shrinkage.
The detection of structural brain damage is complemented by results of functional imaging techniques, such as positron emission tomography (PET) and single photon emission computed tomography (SPECT). By measuring local changes in blood flow and energy metabolism, PET and SPECT can help identify brain regions involved in specific sensory, motor, or thinking functions. Such studies consistently reveal decreased blood flow and metabolic rates in certain brain regions of heavy drinkers compared with those of non-alcoholics, even in the absence of measurable shrinkage. Structural and functional defects revealed by magnetic resonance spectroscopy (MRS) and PET may reflect a decrease in the number or size of neurons or a reduction in the density of communication sites between adjacent neurons.
Recovery of Brain Size and Function
Thinking functions and motor coordination may improve at least partially within 3 to 4 weeks of abstinence accompanied by at least partial reversal of brain shrinkage and some recovery of metabolic functions in the frontal lobes and cerebellum. Frontal lobe blood flow continues to increase with abstinence, returning to approximately normal levels within 4 years.
Relapse to drinking leads to resumption of brain shrinkage, continued declines in metabolism and thinking function, and evidence of neuronal cell damage.
Withdrawal or detoxification. Up to 15 percent of alcoholics experience seizures during withdrawal, and the likelihood of having such seizures, as well as their severity, increases with the number of past withdrawal episodes.