Dementia subtypes

The common causes of dementia are Alzheimer disease (50 to 75% of cases), vascular dementia (20 to 30%), frontotemporal dementias (up to 10%), and dementia with Lewy bodies and Parkinson disease dementia (up to 10%). Many patients have more than one subtype of dementia (mixed dementia); the most common combination is Alzheimer disease and vascular dementia. Less common causes include infections (eg human immunodeficiency virus [HIV]), hazardous alcohol consumption (a significant cause of dementia arising before the age of 65), Huntington disease, Creutzfeldt-Jakob disease and traumatic brain injury.

Dementia subtypes are diagnosed on the basis of early clinical features, patterns of disease progression, and behavioural and psychological features. These diagnoses are probable rather than definite because clinical features of a specific pathology widely vary—cerebral imaging can assist with diagnosis. If possible, seek diagnostic advice from a specialist if a dementia subtype other than Alzheimer disease is suspected. Typical features of common dementia subtypes lists typical features of common dementia subtypes.
Figure 1. Typical features of common dementia subtypes.

[NB1] [NB2]

Memory impairment is prominent early in Alzheimer dementia. As dementia slowly progresses, memory declines further and other symptoms become more prominent, including executive function impairment [NB3].

In dementia with Lewy bodies and Parkinson disease dementia, memory is often initially maintained but deteriorates as dementia slowly progresses. Both dementias are associated with impaired executive function [NB3] and have a gradual, progressive decline with visual hallucinations, fluctuations in arousal and attention, or parkinsonism. REM sleep behaviour disorder often precedes both dementias.

Although features, onset and progression of frontotemporal dementia vary, memory often only deteriorates as dementia progresses. Prominent early symptoms include personality and behavioural changes, and language problems.

Vascular dementia can have a sudden onset (following stroke) or manifest with progressive or stepwise cognitive decline. Symptomatology depends on the nature and location of cerebrovascular disease, but impaired executive function is common [NB3].

Note:

REM = rapid eye movement

NB1: Atypical presentations of dementia subtypes are common and under recognised. If features are atypical, seek expert advice.

NB2: Many patients have more than one subtype of dementia (mixed dementia); the most common combination is Alzheimer disease and vascular dementia.

NB3: Executive functions include problem solving, planning and focusing attention.