assessing different types of dementia is hard, especially in early stages.
there is a handbook put out by the americans psychiatric association
DIAGNOSTIC AND STATISTICAL. MANUAL OF MENTAL DISORDERS, currently in 5th edition. lilink below to some cahpters.
WARNING It is controversial. Many, including me, think it over diagnoses ordinary human diversity as disease. Misuse of psychiatry to suppress dissent is widesoaread in many totalitarian regimes, left, right and fundamentalist https://www.google.co.uk/search?q=dsm+5+pdf&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&ei=9yfIWIH7H4P38Ae0jYDoCA