In frontotemporal dementia, a variety of symptoms are caused by damage to different areas of the frontal and temporal lobes. Based on these symptoms and the lobes that are affected, a person may have one of three types of frontotemporal dementia:
- behavioural variant frontotemporal dementia
- progressive non-fluent aphasia
- semantic dementia.
As with most forms of dementia, the initial symptoms can be very subtle, but they slowly get worse as the disease progresses over several years.
Behavioural variant frontotemporal dementia
This form is diagnosed in about two thirds of people with frontotemporal dementia. During the early stages, changes are seen in the person's personality and behaviour.
A person with behavioural variant frontotemporal dementia may:
lose their inhibitions - behave in socially inappropriate ways and act in an impulsive or rash manner; this could include making tactless or inappropriate comments about someone's appearance
- lose interest in people and things - lose motivation but (unlike someone with depression) they are not sad
- lose sympathy or empathy - become less responsive to the needs of others and show less social interest or personal warmth; this can make the person appear selfish and unfeeling
- show repetitive, compulsive or ritualised behaviours - this can include repeated use of phrases or gestures, hoarding and obsessions with timekeeping
- crave sweet or fatty foods, lose table etiquette, or binge on 'junk' foods, alcohol or cigarettes.
It is common for a person with behavioural variant frontotemporal dementia to struggle with planning and organising or making decisions. These difficulties may first appear at work or with managing finances.
In contrast to Alzheimer's disease, people with early-stage behavioural variant frontotemporal dementia tend not to have problems with day-to-day memory or with visuospatial skills (judging relationships and distances between objects).
It is unusual for a person with behavioural variant frontotemporal dementia to be aware of the extent of their problems. Even early on, people generally lack control over their behaviour or insight into what is happening to them. The symptoms are more often noticed by the people close to them.
Language variants of frontotemporal dementia
In the other two types of frontotemporal dementia, the early symptoms are progressive difficulties with language. These difficulties become apparent slowly, often over two or more years.
In progressive non-fluent aphasia, initial problems are with speech. (Aphasia means loss of language.) Common early symptoms may include:
- slow, hesitant speech - speech may seem difficult to produce and a person may stutter before they can get the right word out, or may mispronounce it when they do
- errors in grammar - a person may have 'telegraphic speech', leaving out small link words such as 'to', 'from' or 'the'
- impaired understanding of complex sentences, but not single words.
In semantic dementia, speech is fluent but people begin to lose their vocabulary and understanding of what objects are. Common early symptoms may include:
- asking the meaning of familiar words (eg 'What is knife?')
- trouble finding the right word, leading to less precise descriptions instead (eg 'the thing for opening tins'), or use of generalised words such as 'animal' instead of 'cat'
- difficulty recognising familiar people or common objects.
In both of the language forms of frontotemporal dementia, other aspects of mental function (memory, visuospatial skills, planning and organising) tend to be well preserved in the early stages.
The rate of progression of frontotemporal dementia varies greatly, from less than two years to 10 years or more. Research shows that on average, people live for about eight years after the start of symptoms.
As frontotemporal dementia progresses, differences between the three types become much less obvious. People with the behavioural variant tend to develop language problems and may eventually lose all speech, like a person with one of the language variants.
Similarly, over several years a person with semantic dementia or progressive non-fluent aphasia will generally develop the behavioural problems typical of behavioural variant frontotemporal dementia.
In the later stages of all forms of frontotemporal dementia, damage to the brain becomes more widespread. Symptoms are often then similar to those of the later stages of Alzheimer's disease. The person may become increasingly less interested in people and things and have limited communication. They may show restlessness or agitation, or behave aggressively. At this late stage someone may no longer recognise friends and family, and is likely to need full-time care to meet their needs.
Overlapping motor disorders
About 10-20 per cent of people with frontotemporal dementia also develop a motor disorder, before or after the start of dementia. A motor disorder is one that causes difficulties with movement. These motor disorders - which are generally uncommon but more likely in this form of dementia - are:
- motor neurone disease
- progressive supranuclear palsy
- corticobasal degeneration.
Their symptoms are similar but can include twitching, stiffness, slow movements and loss of balance or coordination. In the later stages there are often difficulties with swallowing. The three motor disorders share some symptoms with Parkinson's disease.
These motor disorders are all degenerative diseases of the nervous system, meaning that they will get worse over time. The condition of a person with frontotemporal dementia and motor neurone disease can deteriorate quite quickly. On average, a person with both conditions will live for two or three years after diagnosis.