Nuclear Imaging in Frontotemporal Dementia

Frontotemporal dementia (FTD) covers a range of heterogeneous neurodegenerative syndromes, predominantly affecting the frontal and temporal lobes (frontotemporal lobar degeneration or FTLD). Most patients present with behavioural deficits, executive dysfunction and language difficulties. FTD presents as clinically recognized subtypes with behavioural manifestation (FTD-b) and primary progressive aphasia (PPA), which can be divided into semantic dementia (SD), progressive nonfluent aphasia (PNFA) and logopenic aphasia (LPA). FTD is a common type of dementia, particularly at younger age. The underlying neuropathological process of FTLD leads to the clinical phenotype and can be characterized roughly in tauopathy (FTD-TAU) and TAR DNA-binding protein (TDP-43) pathology. Genetics is an important causal factor for FTD, and genetic heterogeneity is reflected by the identification of mutations in causative genes. Diagnostic criteria have modest sensitivity, and it may be challenging to differentiate FTD from psychiatric disorders or other types of dementia, especially AD. Advances in molecular imaging have increased the accuracy of FTD diagnosis, and nuclear imaging techniques improve the understanding of the molecular basis of FTD, which is important to develop rational therapies. Although currently no effective treatment is available for FTD, early and correct diagnosis is necessary for adequate clinical management, because of prognostic implications and for genetic counselling.