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What causes FTD?

FTD is caused by loss of brain cells in the frontal and temporal lobes of the brain. However, the processes that lead to the loss of these brain cells are not well understood. There are a number of different underlying pathological changes that are recognised and several different pathological varieties of FTD. It is known that there is an abnormal accumulation in the brain cells of certain proteins (these include the proteins known as ‘TDP-43’, ‘FUS’ and ‘Tau’) but we do not yet fully understand why this accumulation occurs, or how it leads to the loss of cells.

In somewhere between 30 and 40% of cases a person with the disease may have a family history of the disease in one of their parents, brothers or sisters. In these cases the cause is more likely to be genetic. Problems in the tau (or MAPT) gene, progranulin (or GRN) gene or a gene called C9ORF72 are the cause in some of these cases, but not all abnormal genes have been discovered yet. Genetic testing is available in some centres. Other genes known as VCP, TARDBP, FUS and CHMP2B are extremely rare causes of FTD. Testing for these is not generally clinically available. We have a support group for those families affect by familial FTD (fFTD).

In a small number of patients FTD can overlap with one of a number of diseases that affect movement of the body: motor neurone disease (MND, sometimes called amyotrophic lateral sclerosis, ALS), progressive supranuclear palsy (PSP) or corticobasal degeneration (CBD). Symptoms of MND can include weakness of the limbs or problems with swallowing. PSP causes problems with movements of the eyes as well as problems with thinking and behaviour. There are often other physical problems such as falls, difficulty walking and stiffness. Some patients with FTD will later develop symptoms similar to Parkinson’s disease such as slowing of movements, tremor and stiffness of the limbs.

Early symptoms and diagnosis:

Behavioural variant FTD (bvFTD): The first symptom is usually a change in personality or behaviour (which is out of character for the person) – the symptoms may come on very slowly and not be noticed as definitely abnormal at first.

The symptoms include the following:

  • Loss of inhibitions or increased extroversion. The person may talk to strangers, make inappropriate remarks in public or be rude or impatient. They may also become aggressive.
  • They may spend money excessively.
  • Apathy or withdrawal from social activities.
  • Loss of empathy.
  • Changes in sexual behaviour: either more/less or inappropriate interest.
  • People may be very easily distracted.
  • They often develop fixed routines or become obsessive about things, particularly time (‘clock watching’). Some people begin to hoard things.
  • People may also develop a sweet tooth or a preference for unusual foods. They may also overeat leading to a gain in weight or drink excessive amounts of alcohol. In the later stages people with the illness may compulsively put objects in their mouths.
  • Decreased amount of speech or repetitive speech.
  • Often the person will be unaware of the true extent of the problems and lack insight.

In the early stages memory is often well maintained on psychological but difficulties in organisation and concentration often lead to an apparent memory problem in daily life and so this is also a common complaint.

To try and diagnose bvFTD, behaviour and aspects of thinking (cognitive functions) will be assessed, initially by a doctor, and often followed by a more detailed assessment by a psychologist. Brain scans can show the loss of brain cells in FTD (shrinkage of the affected parts of the brain) but there is no single test that can specifically diagnose FTD with complete reliability during a person’s lifetime. Furthermore, in the early stages of the disease the scan may look normal. Diagnosis is therefore largely based on clinical judgment and FTD can be confused with other disorders in which there are problems with behaviour (e.g. some psychiatric disorders) and with other dementias. The doctor will often arrange blood tests or other tests (usually including detailed brain scans, in particular MRI, and sometimes a lumbar puncture or other specialised tests) to help confirm the clinical diagnosis and rule out diseases that can produce similar symptoms to FTD.

Semantic Dementia (SD): The first symptoms of SD are usually problems with language. These may include:

  • Difficulty finding the right word - often substituting another word or a vague term such as ‘thing’ instead of the specific word.
  • Loss of knowledge of what words mean or what objects are for.
  • People may talk about things in a vague or ‘roundabout’ manner – referred to as ‘circumlocutory’ speech.
  • Difficulty understanding what other people are saying.
  • Problems with reading and writing.

There is no single test that allows doctors to make a diagnosis of SD. Usually the diagnosis is made using a combination of clinical assessment, psychology testing and a brain scan. MRI scanning shows loss of brain cells in the temporal lobe, usually more on the left than the right.

Progressive non-fluent aphasia (PNFA): The first symptoms of PNFA are usually difficulties producing speech. These may include:

  • Difficulty producing words - although the person knows what they want to say, speech may be effortful and words may come out distorted. This is due to difficulties in the co-ordination of the movements of speech and is sometimes called ‘apraxia of speech’.
  • Difficulty organising words - the structure of the sentences may be affected with words being missed out and errors in the grammar.
  • Together these factors make the speech sound distorted, slow and hesitant and difficult to understand.

As with SD, there is no single test that allows doctors to make a diagnosis of PNFA. Usually the diagnosis is made using a combination of clinical assessment, psychology testing and a brain scan. MRI scanning shows loss of brain cells in the speech areas of the brain, particularly the frontal lobe on the left side.

In a small number of people, PNFA is caused by a genetic problem. The genes that are known to cause problems are called progranulin (or GRN) and C9orf72.

Logopenic aphasia (LPA): The main symptoms of LPA are:

  • The main symptoms of LPA are:
  • Difficulty finding the right word. Speech contains pauses where the person stops what they are saying as they try to find the right word.
  • Speech may become slow and hesitant and the pronunciation of words may be affected.
  • As the problem progresses other cognitive functions such as calculation and memory are affected.

There is no single test that allows doctors to make a diagnosis of LPA. Usually the diagnosis is made using a combination of clinical assessment, psychology testing and a brain scan. Brain scanning shows loss of brain cells in areas further towards the back of the brain than the other PPA subtypes, particularly the area where the temporal and parietal lobes meet.