Fixed cognitive impairments are due to a single event. Traumatic brain injury may cause generalized damage to the white matter of the brain or localized damages. A temporary reduction in the supply of blood and oxygen to the brain may lead to this type of dementia. A stroke or brain infection can also be the cause of dementia. Excessive alcoholic intake results in alcoholic dementia. Use of recreational drugs cause substance induced dementia. Once the over use of these drugs are stopped he impairment persists but may not progress. Dementia which begins gradually and worsens progressively over several years is usually caused by neurodegenerative disease; that is, by conditions affecting only or primarily the neurons of the brain and causing gradual but irreversible loss of function of these cells. Less commonly, a non-degenerative condition may have secondary effects on brain cells, which may or may not be reversible if the condition is treated. The causes of dementia depend on the age at which symptoms begin. In the elderly population, a large majority of cases of dementia are caused by Alzheimer's disease, vascular dementia or both. It is rare to have dementia in young people, Among youngsters also the major dementia observed is Alzheimer's disease. People who are affected by frequent head trauma, like boxers and football players are risk of dementia. Other than alcohol, drugs and psychiatric reasons certain genetic disorders also can cause dementia.…