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The Definition of Dementia

by Christine Kennard
for About.com

Updated: September 11, 2006

About.com Health's Disease and Condition content is reviewed by Suman Jayadev, MD

One of the more accurate and widely accepted definitions of dementia (of which Alzheimer's is one type) was produced by a working party of doctors and neuroscientists in the US in 1984.

It goes; 'Dementia is the decline in the memory and other cognitive functions in comparison with the patient's previous level of function as determined by a history of decline in performance and by abnormalities noted from clinical examination and neuropsychological tests'.

A diagnosis of dementia cannot be made when consciousness is impaired or when other clinical abnormalities prevent other adequate evaluation of mental state. Dementia is a diagnosis based on behavior and cannot be determined by brain scan, EEG or other laboratory instruments, although specific causes of dementia may be identified by these means.'

NINCDS-ADRDA (National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association) work group, 1984

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