Frontotemporal dementia (Pick's disease): clinical features and assessment
The clinical presentation in frontotemporal dementia (FTD) reflects the distribution of the pathologic changes rather than the exact histologic subtype of the disease. Three major clinical syndromes can be identified: 1) frontal variant FTD (dementia of frontal type) in which changes in social behavior and personality predominate, reflecting the orbitobasal frontal lobe focus of the pathology. Traditional cognitive tests are insensitive, but more specific measures are under development; 2) semantic dementia (progressive fluent aphasia) in which there is a breakdown in the conceptual database which underlies language production and comprehension, although deficits in nonverbal semantic knowledge can also be shown on neuropsychologic testing. Patients with semantic dementia have asymmetric anterolateral temporal atrophy with relative sparing of the hippocampal formation, which is typically worse on the left side. A variant of this syndrome affecting the right temporal lobe presents with progressive prosopagnosia; 3) progressive nonfluent aphasia in which the phonologic and syntactic components of language are affected in association with left peri-Sylvian atrophy. The assessment of patients with potential FTD involves a multidisciplinary approach. The development of comprehensive caregiver-based neuropsychiatric instruments, neuropsychologic tasks sensitive to semantic memory and other key cognitive impairments, and functional (hexamethyly-propyleneamine-SPECT) and structural (MRI) brain imaging represent significant advances in the field.