Dementia

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erentiated along two dimensions: age and cortical level. The first dimension, age, distinguishes between senile and presenile dementia. Senile dementia is used to describe patients who become demented after the age of 65, whereas presenile dementia applies to patients who become demented prior to that age. Late onset AD (LOAD) also known as senile dementia Alzheimer's type (SDAT) is the predominant cause of senile dementia. Early onset AD (EOAD) is the most frequent cause of presenile dementia, but HD, Pick's disease and Creutzfeldt-Jakob disease though not as frequent are also important causes in presenile dementia.

The second dimension, cortical level, differentiates between cortical and subcortical dementia. Cortical dementia is used to describe dementia which results from brain lesions at the cortical level, whereas subcortical dementia describes dementia resulting from subcortical brain lesions. AD and Pick's disease are the best known examples of cortical dementia; whereas HD, Parkinson's disease (PD), and progressive supranuclear palsy (PSP) are good examples of subcortical dementia (Mayke, 1994). Dementia with both cortical and subcortical features is also possible, in that case the term mixed dementia is used. MID is a common example of mixed dementia.

Pre-Modern Developments

The use of the term dementia dates back to Roman times. The Latin word demens did not originally have the specific connotation that it does today. It meant 'being out of one's mind' and, as such, was a general term for insanity (Pitt, 1987). It was the encylopedist Celsus who first used the word dementia in his De re medicina, published around AD 30. A century later the Cappadocian physician Aretaeus first described senile dementia with the word dotage (i.e., "The dotage which is the calamity of old age...dotage commencing with old age never intermits, but accompanies the patient until death."). Curiously, dementia was mentioned in most systems...