[Diagnosing frontotemporal dementia, a chameleon in psychiatry].
BACKGROUND: Frontotemporal dementia (FTD) generally has a presenile onset, behavioural problems dominate the clinical picture and cognitive functions are still relatively intact. Therefore particularly in the early stages of FTD it is difficult to differentiate this type of dementia from other types of dementia and psychiatric disorders. AIM: To review the options currently available for diagnosing FTD and to evaluate their significance for clinical practice. METHOD: A literature search via PubMed, Embase and the Cochrane Library (1999-2005) using the key words 'frontotemporal dementia' and 'diagnosis' or 'differential diagnosis'. Genetic and post-mortem studies were excluded. RESULTS: The selected literature concerned differential clinical symptoms, neuropsychological research and questionnaires, neuroimaging and fluid abnormalities and dealt mainly with the difference between FTD and other types of dementia but not with differences between FTD and psychiatric disorders. CONCLUSION: Measuring instruments that are helpful for diagnosing FTD are the Manchester Behavioural Questionnaire, the Frontal Behaviour Inventory and the Frontal Assessment Battery. Even better indicators of FTD are asymmetrical frontotemporal structural abnormalities in a CT- or MRI-scan and a decrease infrontal metabolism and perfusion in a PET- or SPECT-scan, although not all detected abnormalities are specific for FTD. Whatever the method used, early diagnosis is difficult; the sensitivity of nearly all diagnostic methods increases as the illness progresses. On the basis of this review of the literature some diagnostic techniques are recommended that can be applied if FTD is suspected.