Alcohol-related Neurological Disease Health Article

Definition

Alcohol-related neurological disease represents a broad spectrum of conditions caused by acute or chronic alcohol intake.

Description

Alcohol, or ethanol, is a poisonous chemical that has direct and toxic effects on nerve and muscle cells. The effects can be profound, and symptoms can include incoordination, weakness, seizures, memory loss, and sensory deficits. Alcohol has a profoundly negative effect on both the central nervous system (i.e., the brain and spinal cord) and the peripheral nervous system (i.e., nerves that send impulses to peripheral structures such as muscles and organs). Alcohol can have negative effects on neurological centers that regulate body temperature, sleep, and coordination.

Alcohol can significantly lower body temperature. It disrupts normal sleep patterns because it decreases rapid eye movement (REM) during the dreaming stage of sleep. It also adversely affects muscle coordination, causing imbalance and staggering—alcohol is a toxic insult to the cerebellum, which is responsible for balance.

Additionally, the chronic use of alcohol can cause a broad spectrum of abnormalities in mental functioning. Generally, persons exhibit poor attention, difficulty with abstraction and problem solving, difficulty learning new materials, reduced visuospatial abilities (capacity to discriminate between two-dimensional or three-dimensional space), and often require extra time to integrate visual information. Other related problems include thiamine deficiency (vitamin B-1) and liver disease (liver cirrhosis and possibly liver cancer).

Acute effects of alcohol

When alcohol is ingested, it moves from the bloodstream into every part of the body that contains water, including the brain, lungs, kidneys, and heart. Alcohol distributes itself equally both inside and outside cells. Ninety-five percent of alcohol is eliminated from the body by breakdown in the liver, and 5% is eliminated through urine, sweat, and breath. Alcohol is broken down (metabolized) in the liver by a complex process called zero-order kinetics (broken down at a certain amount at a time). This means that alcohol is metabolized at a rate of 0.3 oz (8.8 ml) of pure ethanol per hour. Within moments after ingestion, alcohol reaches the brain and produces acute effects such as euphoria, sedation (calmness), anesthesia, and a sleepy hypnotic state. Further effects include release of inhibitions and judgment, blunting of sexual desire, aggressiveness, and mood changes. Physical effects of intoxication (with continued consumption) include impairment of motor ability, muscle function, eyesight, reaction time, night vision, and depth perception. Continued consumption can be lethal because alcohol can depress heart and lung function, which can slow breathing and circulation. Lethality occurs when levels are high enough to paralyze breathing. However, death due to alcohol consumption is rare because body defenses tend to eliminate the chemical by vomiting or the person becomes comatose. Alcohol "hangovers" usually cause persons to have headache (due to dilation of blood vessels in the head), dehydration (alcohol acts as a diuretic increasing urine output), and upset stomach (due to irritation of stomach lining).

Specific neurological damage

The effects of alcohol can include damage or impairment to brain systems and to specific regions in the brain. The limbic system, located deep inside the brain, has several functions, including memory. Long-term users of alcohol often exhibit memory loss due to damage of the limbic system structures called the amygdala and hippocampus, located in the temporal lobes. Damage to other parts of the limbic system can produce symptoms such as abnormalities in emotional functioning and in the ability to use one of the senses (e.g., eyesight or the sense of smell) or in the ability to learn using the senses (e.g., learning through the sense of touch). Damage to the diencephalon (major relay station for nerve signals moving within the brain, associated with memory functioning) occurs and is associated with chronic usage and malnutrition (a late-onset condition). The cerebral cortex (folded outer layer of the brain) is composed of nerve cells called gray matter, which functions as the center of intelligent behavior and higher consciousness. Neuroimaging studies reveal that there are definitive signs of morphological change such as cortical atrophy (a decrease in size of the cerebral cortex). Cortical atrophy induced by alcoholism is associated with deficits in spatial memory and visual associations, learning related to or caused by touch, and problem solving. Alcoholic subjects also exhibit a decrease in blood nourishing the frontal lobe (portion of the brain behind the forehead), whose functions include planning, carrying out, and monitoring goal-directed and socially acceptable behaviors.