Atypical Alzheimer’s disease

Problems with memory are the most common symptom of Alzheimer’s disease, but around 1 in 20 people with Alzheimer’s have different early symptoms. This is called atypical Alzheimer’s disease.

Problems with memory are the most common symptom of Alzheimer’s disease, but around 1 in 20 people with Alzheimer’s have different early symptoms. This is called atypical Alzheimer’s disease. It is caused by the same kinds of changes in the brain as typical Alzheimer’s, but these changes start in a different part of the brain and so cause different symptoms.

The two most common types of atypical Alzheimer’s are frontal variant Alzheimer’s disease (fvAD) and posterior cortical atrophy (PCA).

Frontal variant Alzheimer’s disease (fvAD)

For about 1 in 50 people who have Alzheimer’s disease, the condition affects the frontal lobes of their brain during the earlier stages – something that wouldn’t happen until much later in most typical cases. When this happens, the condition is known as ‘frontal variant Alzheimer’s disease’ (fvAD). For more information on the different lobes of the brain and their functions, see The brain and dementia.

The damage to the frontal lobes can cause:

  • behavioural symptoms (behavioural Alzheimer’s disease) or
  • problems with a type of thinking known as ‘executive function’ (dysexecutive Alzheimer’s disease).

However, most people who have fvAD will show some of both types of symptoms.

A person who has fvAD is likely to show changes in their personality and behaviour. They may:

  • lose their inhibitions – behave in socially inappropriate ways or without thinking. This could include making insensitive or inappropriate comments or invading someone’s personal space, acting in a sexually inappropriate way, staring at strangers, or being verbally or physically aggressive
  • lose motivation to do things that they used to enjoy
  • lose the ability to understand what others might be thinking or feeling, become less sympathetic to the needs of others and show less social interest or personal warmth. They may also show reduced humour and their reactions might be inappropriate, for example laughing at another person’s misfortune
  • show repetitive, compulsive or ritualised behaviours – this can include repeated use of phrases or gestures, hoarding and obsessions with timekeeping. It may also include new interests, such as music or spirituality
  • crave sweet, fatty foods or carbohydrates and forget their table manners. They may also no longer know when to stop eating and drinking.

A person who has fvAD is also likely to have symptoms related to ‘executive function’ and may:

  • struggle with tasks which follow a series of steps – for example making a cup of tea
  • find it hard to think about more than one piece of information at a time when making a decision
  • be easily distracted and find it hard to concentrate
  • sometimes fixate on a specific thought or on something in the room
  • copy other people’s behaviour.

Some people who have the condition may also have memory problems, but these are generally much less severe during the earlier stages than in typical Alzheimer’s disease.

Sometimes fvAD is misdiagnosed as a more common type of dementia that affects the frontal lobes of a person’s brain. This can include vascular dementia or behavioural variant frontotemporal dementia.

As with other types of Alzheimer’s disease, there is no treatment that can slow the progression of fvAD. Drugs such as donepezil, rivastigmine and galantamine may improve a person’s symptoms. In people with other types of dementia, such as typical Alzheimer’s disease, they can help a person to think more clearly. However, there haven’t been any clinical trials to test how well these drugs work for people who have fvAD. This is because it is a rare type of dementia and is very difficult to diagnose correctly.

People who have frontal variant Alzheimer’s disease are often given similar treatment to people with behavioural variant frontotemporal dementia. For more information see Frontotemporal dementia: what is it?

Posterior cortical atrophy (PCA)

Posterior cortical atrophy (PCA) is most often caused by the same changes in a person’s brain that cause Alzheimer’s disease. However, in PCA the disease starts in a different part of the brain. At first it mainly affects the back of the brain – a region called the ‘visual cortex’. This part of the brain processes information that comes from a person’s eyes and turns it into what the person sees. For more information see The brain and dementia. PCA can also be caused by other types of disease that affect a person’s visual cortex, but this is less common.

A person who has PCA will usually start to have symptoms between the ages of about 55 and 65. The first signs are often subtle problems with their vision. It can take a long time to confirm that sight problems are caused by damage to the brain rather than by eye problems. This means there may be a delay of several months or even years before the person gets an accurate diagnosis of PCA. This can cause a lot of frustrationand worry.

In the early stages of PCA, a person will have problems with their vision that become more serious over time. These may include:

  • difficulty recognising faces and objects in pictures
  • finding it hard to judge distances
  • having problems with spatial awareness.

A person who has PCA may be able to think clearly for several years after they are diagnosed. However, they may have increasing problems with reading, writing, spelling and arithmetic. They may also find it difficult to use digital technology, such as computers or mobile devices. PCA can cause problems with vision which may mean a person can no longer drive safely. A person’s vision is likely to become increasingly distorted and they are likely to need support with most visual activities. In the later stages of PCA many people are registered blind due to them becoming increasingly
visually impaired as the disease progresses.

Over time the disease that causes PCA can start to affect other parts of the brain. This causes symptoms that are more common in people with typical Alzheimer’s disease, such as:

  • memory loss
  • confusion
  • difficulties with communication.

During the late stages of PCA, a person is likely to have care needs that are similar to people with late-stage Alzheimer’s disease. There are no specific drugs to treat PCA. However, some of the symptoms to do with thinking and memory may improve slightly if they take the drugs donepezil, rivastigmine or galantamine. If the person has depression or other symptoms related to their mood, these are often treated with
antidepressant medication.

Rare Dementia Support has a website with detailed information for people affected by PCA. They also have a PCA Support Group Adviser who can be contacted by phone or email. For more information see Rarer types of dementia - other resources.