If you go to this link http://www.healthcentral.com/alzheimers/c/57548/77542/alzheimer-types, you'll find Christine Kennard did a wonderful job of explaining the differences in the many types of dementia.

Carol

Dementia can be looked at as an umbrella term which describes the range of symptoms a person can exhibit due to brain degeneration. These can include memory loss, impairments in judgment, lack of attentiveness, repetitive speech, changes in mood and personality, inability to perform daily activities, loss of initiative, and other physical and cognitive changes. Dementia can interfere with an individual’s capacity to perform daily functions independently, ranging anywhere from financing to driving to personal hygiene. There are dozens of causes of dementia, some which are reversible and others which are treatable. Alzheimer’s disease is a form of dementia which cannot be reversed, and happens to be the most common form of dementia in people 65 and older – it accounts for about 60% of all dementias. Alzheimer’s disease causes damage to brain cells over time which results in symptoms of dementia. If an individual is diagnosed as having dementia, it is helpful to pursue further testing in order to pinpoint the type of dementia he or she has. This can help the person learn more about their options and pursue the best possible treatment available.