Year: 2012
Type: article
Abstract: Frontotemporal dementia (FTD) is an umbrella term for three neurobehavioral syndromes associated with neurodegeneration in the frontal and anterior temporal lobes. Patients present with progressive decline in social and emotional function in the behavioral-variant (bvFTD); with progressive loss of word and object meaning in semantic-variant primary progressive aphasia (svPPA); or with gradual decline in motor speech and grammar in non-fluent/agrammatic variant PPA (nfvPPA). The underlying pathologic substrate involves aggregation of tau, TDP-43, or (rarely) FUS inclusions. Neuroimaging plays an important role in diagnosis and has helped elucidate the neuroanatomic basis of the clinical deficits. This presentation will provide an overview of neuroimaging in FTD. On structural and functional imaging, bvFTD patients show symmetric or right-predominant changes in frontoinsular cortex, anterior cingulate, orbitofrontal and dorsolateral prefrontal regions. svPPA is associated with (often asymmetric) changes in the temporal poles, while nfvPPA patients show lesions in left posterior frontoinsular cortex. Correlative imaging studies in FTD have demonstrated the importance of medial prefrontal cortex and right temporal pole in social-emotional cognition, dorsolateral prefrontal cortex in executive function, the bilateral temporal poles in semantic memory, and left posterior frontoinsular cortex in speech production and grammar. In new consensus criteria, a typical neuroimaging pattern is required for a diagnosis of probable bvFTD, and is considered supportive in diagnosing variants of PPA. FTD can be distinguished from Alzheimer's disease (AD) on MRI, FDG-PET or SPECT based on sparing of lateral parietal regions and posterior cingulate/precuneus, though amyloid PET may provide even more reliable discrimination. Neuroimaging has been less helpful in discriminating between pathologic subtypes of FTD. Resting-state fMRI may be sensitive to early changes in network connectivity, including in pre-symptomatic FTD gene mutation carriers. A multi-site, multi-modality longitudinal study of FTD has been launched in the U.S. to optimize the integration of neuroimaging into future drug trials. FTD can be diagnosed and distinguished from AD with high accuracy using modern neuroimaging techniques, though novel markers will be needed to reliably discriminate between FTD pathologic subtypes. As in AD, early detection and sensitive longitudinal tracking are important goals for future imaging research.
Source: Alzheimer s & Dementia
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2135525907