Mixed dementia
An estimated 10 per cent of people with dementia have more than one type at the same time. This is called mixed dementia. The most common combination is Alzheimer’s disease with vascular dementia (caused by problems with the blood supply to the brain). The symptoms of this kind of mixed dementia are a mixture of the symptoms of Alzheimer’s disease and vascular dementia.
Atypical Alzheimer’s disease
In some people with Alzheimer’s disease the earliest symptoms are not memory loss. This is called atypical Alzheimer’s disease. The underlying damage (plaques and tangles) is the same, but the first part of the brain to be affected is not the hippocampus.
Atypical Alzheimer’s disease is uncommon in those diagnosed when they are over 65. It accounts for around five per cent of all Alzheimer’s in this age group. It is, however, more common in people diagnosed when they are under 65 (early-onset Alzheimer’s disease). In this age group it represents up to one-third of cases.
The atypical forms of Alzheimer’s disease are as follows:
Posterior cortical atrophy (PCA) occurs when there is damage to areas at the back and upper-rear of the brain. These are areas that process visual information and deal with spatial awareness. This means the early symptoms of PCA are often problems identifying objects or reading, even if the eyes are healthy. Someone may also struggle to judge distances when going down stairs, or seem uncoordinated (for example when dressing).
Logopenic aphasia involves damage to the areas in the left side of the brain that produce language. The person’s speech becomes laboured with long pauses.
Frontal variant Alzheimer’s disease involves damage to the lobes at the front of the brain. The symptoms are problems with planning and decision-making. The person may also behave in socially inappropriate ways or seem not to care about the feelings of others.
Who gets Alzheimer’s disease?
Most people who develop Alzheimer’s disease do so after the age of 65, but people under this age can also develop it. This is called early-onset Alzheimer’s disease, a type of young-onset dementia. In the UK there are over 40,000 people under the age of 65 with dementia.