Frontotemporal dementia can be hard to diagnose, because it is relatively uncommon and does not initially cause memory problems. The person with FTD may lack insight into their behaviour, and so they may not want to seek professional help. Doctors may also not suspect dementia in what is often a middle-aged person.
Frontotemporal dementia may be misdiagnosed as atypical Alzheimer’s disease (a form of Alzheimer’s disease in which people don’t have early memory loss). The behavioural symptoms may easily be mistaken for depression, schizophrenia or obsessive-compulsive disorder. Problems with language or movement may be misdiagnosed as stroke.
Blood tests and a thorough physical examination are important to rule out other possible causes of symptoms. A specialist may suspect a diagnosis of FTD after questioning the affected person and someone who knows them well. The specialist will take a detailed history of the person’s symptoms and gather information to gain a wider picture of the person’s behaviour and functioning in their daily life.
Standard tests of mental abilities, which tend to focus on memory loss, can be less helpful in the diagnosis of FTD. More specialised tests of social awareness or behaviour may be needed.
CT (computerised tomography) and MRI (magnetic resonance imaging) scans of the brain should be used to assess the pattern of damage. They can also rule out other possible causes of a person’s symptoms, such as a stroke or tumour. If further tests are needed, more specialised brain scans will be carried out, such as PET (positron emission tomography) and SPECT (single photon emission computerised tomography) to measure the person’s brain activity. These scans are useful as they may detect reduced activity in the frontal and/or temporal lobes before a CT or MRI scan can detect structural changes to these lobes. Further tests may include a lumbar puncture, which involves collecting and analysing fluid from the spine and is carried out mainly in younger people.
Where a person is suspected of having a strongly inherited form of FTD, genetic testing may be able to confirm the diagnosis. This could then allow family members to find out whether they will go on to develop the condition in their lifetime. The decision to find out is up to the individual and support is available.
After a person dies, it is possible to make a pathological diagnosis of FTD, as the changes to the brain can be directly seen at a post-mortem.