There are many things that people do not generally know about dementia. Two main things that people may not know are that dementia is actually a progressive neurological condition and that there are many different types of dementia. Here I hope to explain to you the different types of dementia and what features they have.
Alzheimer’s Disease (AD) is the most common form of dementia and accounts for approximately 60% of cases of dementia in Australia. This is the form of dementia that most people are familiar with. The main feature of AD is memory loss, though it also has many other features including dysphasia (language problems), dyspraxia (difficulty with movement), agnosia (problems with object recognition) and dyscalculia (difficulty with numbers). Executive functions often also deteriorate, such as problem solving, abstract thought, planning, organization, judgement and insight. There are also changes in behavior, personality and mood which family and carers often find most distressing.
Established risk factors for AD include increasing age, Down’s syndrome, family history of dementia (50% of people with dementia) and a specific genotype (APOE). Likely risk factors include female gender, history of head injury, family history of Down’s syndrome, high blood pressure, and low educational level. It has a gradual onset with a progressive decline, and tends not to present as fluctuations in cognition.
Vascular Dementia is the term used to describe the cognitive changes associated with cerebrovascular disease. That is, changes caused by “mini strokes” in the brain. The features of vascular dementia are many and varied depending upon the location on the brain of the lesions. Features may include, but are not limited to; memory loss, slowed cognitive processing, impairment of problem solving and judgement, behavioural changes including apathy and depression, gait changes, falls, incontinence, and emotional changes. There can be either a sudden or gradual onset, and there tends to be variations in cognition, with nocturnal confusion.
Lewy Body Dementia presents with very similar features to Parkinson’s disease due to the part of the brain affected, and accounts for up to 20% of dementia. It has a more rapidly progressing course, though can fluctuate significantly. Common features include hallucinations and delusions, rigidity, slowness of movement and gait changes. The Parkinsonian features of Lewy Body Dementia often respond to Parkinson’s medications.
Frontal Lobe Dementia is so called as it affects the frontal lobes (front area) of the brain. The most common deficit is seen in executive function such as problem solving, judgement and insight, as well as behaviour changes such as social disinhibition and personal neglect. Unfortunately, this type of dementia usually appears at a younger age, often when the individual is still working.
Secondary Neurodegenerative Dementia is the dementia that results directly from a neurodegenerative disorder. These include Parkinson’s disease, progressive supranuclear palsy, normal pressure hydrocephalus, Huntington’s disease, corticobasal degeneration, multiple sclerosis, motor neuron disease and AIDS.
With approximately 50% of people over 65 having some form of dementia, and the ageing population, dementia is fast becoming a major public health issue. It has implications for both the health and aged care sectors, as well as other aspects of community life.
Hecker, J. (1997). What’s new in dementia? Modern Medcine; August, 30-45.