What is Dementia? Dementia is an organic brain syndrome which results in global cognitive impairments. Dementia can occur as a result of a variety of neurological diseases. Some of the more well known dementing diseases include Alzheimer's disease (AD), multi-infarct dementia (MID), and Huntington's disease (HD). Throughout this essay the emphasis will be placed on AD (also known as dementia of the Alzheimer's type, and primary degenerative dementia), because statistically it is the most significant dementing disease occurring in over 50% of demented patients (see epidemiology). The clinical picture in dementia is very similar to delirium, except for the co