Dementia is an acquired disorder of higher cerebral functions and cognition. Because of increasing life expectancy dementia poses a major health and socio economic problem. Alzheimer's disease accounts for 70-90% of mental decline in the elderly. Degenerative non-Alzheimer's dementi as are responsi ble for 7-30%. These include a variety of disorders clinically characterised by progressive cognitive dysfunction often combined with focal neurological def icits, e.g. Parkinson-plus syndromes, Lewy body dementia, lobar and multisys tem atrophies, other neurodegenerative disorders, and prion...