[Frontotemporal dementia and frontotemporal degeneration--how to define?]

The term of the frontotemporal dementia was first proposed by Lund and Manchester group in 1994, but the definition of frontotemporal dementia has been still controversial. Frontotemporal dementia is caused by several diseases which have fronto-temporal atrophy. The diseases are collectedly designated as frontotempoal degeneration. The frontotemporal degeneration encompasses several diseases such as Pick disease (frontotemporal degeneration with Pick bodies) and frontotemporal degeneration with ubiquitin-positive inclusions and frontotemporal degeneration (no inclusion bodies are observed). Pick bodies are consisted of abnormally phosphorylated tau protein. The recent discoveries of tau mutations in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) suggest important role of tau abnormalities in the disease mechanism. The frontotemporal degeneration has also another clinical phenotype such as slowly progressive aphasia. Slowly progressive aphasia has subtypes of non-fluent aphasia and semantic aphasia. Some patients with corticobasal degeneration or progressive supranuclear palsy also reveal the clinical pictures of frontotemporal dementia or slowly progressive aphasia and should be considered as differential diagnosis in the patients with frontotemporal dementia or slowy progressive aphasia.