02 Types of dementia
There are over 100 different types of dementia
All types of dementia are progressive, which means that the functioning of the brain will change over time. However, each type of dementia affects everyone differently and with the right support, it is absolutely possible to live well with dementia. In this section, you’ll find information about the most common types of dementia, the symptoms and the causes for each type.
Cortical and subcortical dementia
Medical professionals sometimes categorise dementia into cortical and subcortical dementia.
Cortical dementia is typically associated with the brain’s grey matter, which is the characteristic outer structures of the brain. These outer structures have an important role in processing information and in functions such as language and memory. Types of cortical dementia include Alzheimer’s, frontotemporal dementia, Binswanger’s disease and Creutzfeldt-Jakob disease.
Subcortical dementia initially affects structures below the cortex in the innermost parts of the brain known as white matter. These inner structures responsible for controlling the speed of thought processes and emotions. Types of subcortical dementia include Huntington’s disease, Parkinson’s dementia, and AIDS dementia complex.
The progression of dementia is not necessarily affected by category or type, but a variety of factors including lifestyle, health and genetics.
The most common types of dementia
To date, research has discovered over 100 types of dementia. The most common types of diagnosis in the UK are:
Alzheimer’s is the most commonly diagnosed type of dementia in the UK. 60-80% of those living with dementia have Alzheimer’s and this is perhaps why there’s widespread misuse of the two terms, which are often incorrectly used interchangeably. Alzheimer’s is a type of dementia. With Alzheimer’s disease, abnormal proteins called plaques and tangles simultaneously damage the internal and external structures of brain cells. In time, the damage caused by abnormal proteins disrupts the chemical connections between brain cells, meaning they are unable to communicate information around the brain and body and eventually causing brain cells to die.
The narrowing or blockage of blood vessels restricts the bloodflow and oxygen supply to the brain. With a limited oxygen supply, the cells in the brain are not able to respire, causing them to become damaged or die. The symptoms of vascular dementia can occur suddenly, following one large stroke or they can develop over time, after a series of smaller strokes.
Vascular dementia can also be caused by disease affecting the small blood vessels deep in the brain, known as subcortical vascular dementia.
With mixed dementia, more than one type of dementia occurs simultaneously in the brain. The most common types of dementia to occur simultaneously are Alzheimer’s disease (caused by abnormal proteins called plaques and tangles which destroy nerve cells in the brain) and the blood vessel changes associated with vascular dementia. Several types of dementia can often coexist in the brain, such as Alzheimer’s, vascular dementia, and dementia with Lewy bodies.
Dementia with Lewy bodies (DLB)
Dementia with Lewy bodies is caused by abnormal protein structures called Lewy bodies (alpha-synuclein) that appear in nerve cells in the brain. Researchers don’t yet have a full understanding of why Lewy bodies appear, but DLB is linked to low levels of important chemicals (mainly acetylcholine and dopamine) that carry messages between nerve cells, causing a loss of connections between nerve cells. Lewy bodies disrupt the cells’ ability to transmit information around the brain and body, causing them to die.
Frontotemporal dementia (FTD)
The name ‘frontotemporal’ comes from the areas of the brain which are affected. With frontotemporal dementia, the build-up of abnormal proteins inside the nerve cells in the front and side areas of the brain interrupt the communication between cells, reducing the information sent around the brain and body, eventually causing the cells to die.
The symptoms of frontotemporal dementia vary depending on what area of the brain is affected:
Two-thirds of people with FTD are diagnosed with behavioural variant. Unlike Alzheimer’s, the early stages of behavioural FTD doesn’t affect day-to-day memory or perception. During the early stages of behavioural FTD, changes personality and behaviour become noticeable.
- There are two further types of frontotemporal dementia, both of which affect the language functions of the brain. These difficulties with language become apparent slowly, often over a couple of years:
- Aphasia – language loss with common symptoms including difficulties in speech production such as stuttering or mispronunciation, grammatical errors and impaired understanding.
- Semantic dementia – Although speech may be fluent, the vocabulary begins to decline and symptoms include confusion regarding the meaning of familiar words, difficulty in finding the right word or recognising familiar objects.
- Motor disorders – About 10–20 percent of people with FTD also develop a motor disorder, which causes difficulties with movement. These motor disorders include motor neurone disease, progressive supranuclear palsy and corticobasal degeneration. These three conditions share similar symptoms such as twitching, stiffness, slow movements and loss of balance or coordination.
As the FTD progresses, more of the brain becomes damaged and the differences between the types of FTD become less obvious. Later stages of FTD begin to share symptoms with Alzheimer’s disease, such as confusion, disorientation, memory loss and changes in behaviour.