Traditionally Alzheimer disease has been clinically characterised by predominantly memory deficits, at least in initial stages. It has become increasingly evident that in addition to the typical presentation, a number of atypical clinical patterns, which are nonetheless pathologically Alzheimer disease, exist.
Classical/typical Alzheimer disease
The typical patient with Alzheimer disease will present initially with antegrade episodic memory deficits. Over time (often years) the disease progresses with eventual involvement of attentional and executive processes, semantic memory, praxis and visuoperceptual abilities. Neuropsychiatric symptoms are also common and eventually affect almost all patients. These include apathy, depression, anxiety, aggression/agitation, and psychosis (delusions and hallucinations).
Atypical/variant Alzheimer disease
These entities, often recognised clinically well before they were identified to be pathologically identical to Alzheimer disease are characterised by slowly progressive focal cortical atrophy, with symptoms and signs matched to the affected area 1. Examples include:
- posterior cortical atrophy
- a frontal variant of Alzheimer disease
- a minority of cases with predominant semantic dementia