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Can alcoholism cause dementia?
Everyone is aware of the phenomenon known as the "blackout" — a transient period of memory loss or amnesia during intoxication with no real evidence of neurological injury. It generally coincides with a rapid, rather than slow, elevation of blood alcohol and may be an early predictor of alcohol dependence. Repeated episodes have long-term consequences with respect to memory impairment. Because of alcohol's intoxicating effects, there can be long-term consequences to the brain in particular and the nervous system in general. The damaging effects can be far reaching. They are due both to alcohol's direct toxic effects, but also to its indirect effects through the various nutritional and metabolic abnormalities as well as the resulting withdrawal syndrome. The various neurological effects are discussed.
Everyone is aware of the phenomenon known as the "blackout" — a transient period of memory loss or amnesia during intoxication with no real evidence of neurological injury.
Probably the most well-known, although not the most common, form of memory disturbance caused by alcohol is Wernicke's encephalopathy and Korsakoff's dementia. Wernicke's encephalopathy refers to an acute disease process caused by thiamine deficiency, leading to confusion, apathy, drowsiness, an unsteady gait, and visual disturbances, due to nerve palsy's affecting the motor system of the eyes. When memory loss for events after the onset of the disorder occurs on a chronic basis (known as anterograde amnesia), it is referred to as Korsakoff's dementia. Often individuals suffering from this will fill these memory gaps with events that never occurred. This is known as confabulation and is different from lying in that there is no real ulterior motive behind it. Korsakoff's is not a true dementia in that it does not affect other areas of cognition in the same manner that Alzheimer's disease does. The more proper term for this condition therefore is alcohol amnestic disorder. Both Wernicke's and Korsakoff's begin when heavy drinking causes intestinal malabsorption and thiamine (vitamin Bl) deficiency. Treatment involves administration of thiamine 100 mg daily over 3 months. Untreated, it carries a mortality rate of 15%. Even with treatment, only a third of those with memory impairment fully recover.
Alcohol has a direct neurotoxic effect on the brain, accelerating to a generalized atrophy or shrinkage of the brain that often occurs with aging. Some studies suggest that this process may be reversible and that abstinence may aid in halting the progression and even reversing it. Apparently, alcohol attacks the coating of the nerve cells, known as glial cells that make up the myelin, or white matter, rather than the nerve cells themselves. Unlike neurons themselves, glial cells have the capacity to regenerate. Other studies, however, have disputed this. What is known is that the progression of alcohol dementia can be halted with abstinence, unlike the progression of Alzheimer's disease, which continues to progress. Most studies support the contention that alcohol does not hasten the progress of Alzheimer's disease, and it is doubtful that alcohol is a risk factor in the development of early Alzheimer's, although this remains somewhat controversial.
Complicating this picture, however, is the fact that many times the dementia is not reversible. Alcoholics can develop Alzheimer's disease, and any damage that alcohol has caused to the brain of an Alzheimer's patient will worsen the condition. What is not controversial is the fact that alcoholism can increase the risk of stroke for the very same reason that it increases the risk of heart attack, as the two processes are essentially identical though they involve different organs. One of the most common forms of dementia is vascular dementia. Many times strokes are undetected because the blood clots or thrombi are so small that they affect only the tiniest of blood vessels. This leads to a condition that can be seen on brain imaging scans known as microvascular changes that can also lead to brain atrophy and dementia without the obvious signs of stroke. Finally, alcoholics are prone to accidents that frequently involve the head. One head injury dramatically increases the risk for another head injury Multiple head injuries increase the risk of developing traumatic brain injury which invariably leads to multiple cognitive and personality changes that can be viewed as dementia. Up to 30% of nursing home patients have alcohol-related dementia due to any of the previously mentioned problems.
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