DEMENTIA

chronic, usually progressive deterioration of intellectual functions, usually owing to pathological changes in the brain. Dementia is most commonly seen in the elderly and usually begins with the loss of short-term memory; other initial manifestations can include confusion, irritability, and personality disturbance. Dementia was formerly distinguished from senility, which was considered to affect those over age 65; the term presenile dementia, or Alzheimer's disease, was reserved for younger patients. However, it is now recognized that the same symptoms occur in all victims of dementia regardless of age. The largest number of those with dementia have the irreversible, degenerative brain disease known as Alzheimer's disease (q.v.). These individuals first lose recent memory and higher intellectual functions such as judgment and abstract reasoning, then develop more severe memory losses leading to spatial and temporal disorientation. They may become emotionally unstable and deteriorate physically as well as mentally, ultimately losing even the ability to speak coherently. Dementia is also present in another degenerative brain disease, Pick's disease (q.v.). The most significant other cause of dementia is cerebral arteriosclerosis, which accounts for 20 percent of all cases. Dementia is often a feature in cases of Huntington's chorea, and the syndrome is prominent in cases of paresis (q.v.) and some types of encephalitis. Treatable dementias occur in hypothyroidism, other metabolic diseases, and some malignant tumours. Treatment of the underlying disease in these cases may arrest the progress of dementia but usually does not reverse it. About 1020 percent of all cases of dementia result from such treatable diseases.