1. The general criteria for dementia G1–G4 must be met.
2. There is no evidence from the history, physical examination, or special investigations for any other possible cause of dementia (e.g., cerebrovascular disease, HIV disease, Parkinson's disease, Huntington's disease, normal pressure hydrocephalus), a systemic disorder (e.g., hypothyroidism, vitamin B₁₂ or folic acid deficiency, hypercalcemia), or alcohol or drug abuse.

Comments
The diagnosis is confirmed by postmortem evidence of neurofibrillary tangles and neuritic plaques in excess of those found in normal aging of the brain.
The following features support the diagnosis, but are not necessary elements: involvement of cortical functions as evidenced by aphasia, agnosia, or apraxia; decrease of motivation and drive, leading to apathy and lack of spontaneity; irritability and disinhibition of social behavior; evidence from special investigations that there is cerebral atrophy, particularly if this can be shown to be increasing over time. In severe cases there may be Parkinson-like extrapyramidal changes, logoclonia, and epileptic fits.
Specification of features for possible subtypes
Because of the possibility that subtypes exist, it is recommended that the following characteristics be ascertained as a basis for a further classification age at onset; rate of progression; configuration of the clinical features, particularly the relative prominence (or lack) of temporal, parietal or frontal lobe signs; any neuropathological or neurochemical abnormalities, and their pattern.
The division of Alzheimer's disease into subtypes can at present be accomplished in two ways: first by taking only the age of onset and labeling the disease as either early or late, with an approximate cutoff point at 65 years; or second, by assessing how well the individual conforms to one of the two putative syndromes, early- or late-onset type.
It should be noted that a sharp distinction between early- and late-onset types is unlikely. Early-onset type may occur in late life, just as late-onset type may occasionally have an onset before the age of 65. The following criteria may be used to differentiate dementia in Alzheimer's disease with early and late onset, but it should be remembered that the status of this subdivision is still controversial.
Dementia in Alzheimer's disease with early onset

1. The criteria for dementia in Alzheimer's disease must be met, and the age at onset must be below 65 years.
2. In addition, at least one of the following requirements must be met:
   1. evidence of a relatively rapid onset and progression;
   2. in addition to memory impairment, there must be aphasia (amnesic or sensory), agraphia, alexia, acalculia, or apraxia (indicating the presence of temporal, parietal, and/or frontal lobe involvement).

Dementia in Alzheimer's disease with late onset

1. The criteria for dementia in Alzheimer's disease must be met and the age at onset must be 65 years or more.
2. In addition, at least one of the following requirements must be met:
   1. evidence of a very slow, gradual onset and progression (the rate of the latter may be known only retrospectively after a course of 3 years or more);
   2. predominance of memory impairment G1(1), over intellectual impairment G1(2) (see general criteria for dementia).

Dementia in Alzheimer's disease, atypical or mixed type
This term and code should be used for dementias that have important atypical features or that fulfill criteria for both early- and late-onset types of Alzheimer's disease. Mixed Alzheimer's and vascular dementia are also included here.
Dementia in Alzheimer's disease, unspecified