Specific Imaging Findings

The role of imaging in the evaluation of frontotemporal lobar degeneration (FTLD) is to exclude other forms of dementia such as Alzheimer disease and vascular dementia. FTLD typically shows selective atrophy of the anterior temporal and frontal lobes with relatively preserved occipital and parietal lobes. The involvement is often asymmetric, with the dominant hemisphere more severely affected. Diffuse brain atrophy may also be observed. FDG-PET in FTLD demonstrates decreased glucose uptake in the frontal and temporal cortices.

Pertinent Clinical Information

FTLD is the second most common type of dementia in individuals under 65 years of age with a prevalence of 15 per 100 000 in the 45–64 year age range. It is a primary neurodegenerative disease characterized by the development of progressive behavioral change, executive dysfunction and language deficits with relatively preserved memory in the early stages. FTLD comprises three clinical subtypes: (1) frontotemporal dementia (FTD, also known as Pick's disease) or the frontal variant, the most common form, characterized by early personality changes such as apathy and indifference, impulsive behaviors and disinhibition, and poor judgment; (2) semantic dementia (SD) characterized by early loss of word meaning but fluent speech; (3) progressive nonfluent aphasia (PNFA) characterized by loss of speech fluency with anomia (primary progressive aphasia). The differential diagnosis between AD and FTLD can be difficult in the early stages and the clinical overlap between these conditions highlights the importance of neuroimaging, along with neuropsychological testing.