[Diagnostic criteria for fronto-temporal lobe degeneration]

Circumscribed atrophy of the frontal and temporal lobes (frontotemporal lobar degeneration) accounts for about one fifth of cases of primary degenerative dementia occurring before the age of 65. It produces three prototypical clinical syndromes. The most common is frontotemporal dementia, characterized by personality change and profound alteration in social conduct and associated with bilateral atrophy of the frontal and anterior temporal lobes. Progressive non-fluent aphasia is characterized by difficulty in verbal expression, anomia and phonemic errors in the presence of relative preservation of comprehension and associated with atrophy predominantly of the left hemisphere. In semantic dementia there is fluent speech with semantic errors and severely impaired comprehension and naming, together with a visual associative agnosia, resulting from bilateral atrophy of the inferior and middle temporal gyri. The clinical syndromes occur with either of two main histological types: prominent microvacuolar change, without specific histological features (frontal lobe degeneration-type), severe astrocytic gliosis with or without ballooned cells and inclusion bodies (Pick-type). To improve clinical recognition and advance understanding of this relatively common form of cerebral degeneration, members of an international workshop on Frontotemporal Lobar Degeneration developed consensus criteria, building upon earlier published clinical diagnostic guidelines for frontotemporal dementia. The consensus criteria reported here specify core and supportive features for each of the prototypical clinical syndromes: frontotemporal dementia, progressive aphasia and semantic dementia, as well as providing broad inclusion and exclusion criteria for the generic entity of frontotemporal lobar degeneration.