Types of Dementia
Alzheimer’s disease is the most common cause of dementia and accounts for 50%-75% of all cases. It destroys brain cells and nerves disrupting the transmitters which carry messages in the brain, particularly those responsible for storing memories. Alzheimer’s disease was first described by Alois Alzheimer in 1906.
During the course of Alzheimer’s disease, nerve cells die in particular regions of the brain. The brain shrinks as gaps develop in the temporallobe and hippocampus, which are responsible for storing and retrieving new information. This in turn affects people’s ability to remember, speak, think and make decisions. The production of certain chemicals in the brain, such as acetylcholine is also affected. It is not known what causes nerve cells to die but there are characteristic appearances of the brain after death. In particular, ‘tangles’ and ‘plaques’ made from protein fragments are observed under the microscope in damaged areas of brain. This confirms the diagnosis of Alzheimer’s disease.
Typically, Alzheimer’s disease begins with lapses of memory, difficulty in finding the right words for everyday objects or mood swings. As Alzheimer’s progresses, the person may:
-Routinely forget recent events, names and faces and have difficulty in understanding what is being said
-Become confused when handling money or driving a car
Undergo personality changes, appearing to no longer care about those around them
Experience mood swings and burst into tears for no apparent reason, or become convinced that someone is trying to harm them
As the disease progresses, people may also:
Adopt unsettling behaviour like getting up in the middle of the night or wander off and become lost
Lose their inhibitions and sense of suitable behaviour, undress in public or make inappropriate sexual advances
Vascular disease occurs where blood vessels are damaged and the supply of oxygen is at risk. If oxygen supply fails in the brain, brain cells are likely to die leading to a series of mini strokes (infarcts) and possible vascular dementia.Vascular dementia accounts for 20%-30% of all cases of dementia.
The mini strokes that cause vascular dementia are often so slight that they cause no immediate symptoms, or they may cause some temporary confusion. However, each stroke destroys a small area of cells in the brain by cutting off its blood supply and the cumulative effect of a number of mini strokes is often sufficient to cause vascular dementia. Vascular dementia and Alzheimer’s disease frequently occur together and they may often act in combination to cause dementia.
-Cognitive decline is likely to have a clear start date and symptoms tend to progress in a series of steps following each attack, suggesting that small strokes have been occurring
-May include severe depression, mood swings and epilepsy
-Some areas of the brain may be more affected than others. Consequently, some cognitive abilities may be relatively unaffected
Dementia with Lewy bodies
Dementia with Lewy bodies is similar to Alzheimer’s disease in that it is caused by the degeneration and death of nerve cells in the brain. It takes its name from the abnormal collections of protein, known as Lewy bodies, which occur in the nerve cells of the brain.Half or more of people with Lewy body disease also develop signs and symptoms of Parkinson’s disease. People with Lewy body disease are very sensitive to some tranquillisers known as antipsychotic or neuroleptic drugs and their use should be avoided if at all possible.
Dementia with Lewy body affects:
-Concentration and attentionMemory
-LanguageThe ability to judge distances
-The ability to reason
-People with Lewy body disease can experience visual hallucinations
Fronto-temporal dementia (including Pick’s disease)
Fronto-temporal dementias are a relatively rare cause of dementia and typically develop at an earlier age than Alzheimer’s disease, usually in a person in their forties or fifties. The frontal lobe of the brain is particularly affected in early stages.Frontal lobe dementia is caused in a similar way to Alzheimer’s disease in that it involves a progressive decline in a person’s mental abilities over a number of years. Damage to brain cells is more localised than in Alzheimer’s disease and usually begins in the frontal lobe of the brain.
-The frontal lobe governs people’s mood and behaviour. The person’s mood and behaviour may become fixed and difficult to change, making them appear selfish and unfeeling
-The person does not usually have sudden lapses of memory which are characteristic of Alzheimer’s disease.