Frontotemporal Dementia

Frontotemporal dementia (FTD) is a recently used terminology for clinical Pick's disease (PiD). Arnold Pick (1892) described aphasia and personality changes with progressive frontal and temporal degeneration, but later it became a pathological entity defined histologically by the presence of argyrophilic globular inclusions (Pick bodies) and swollen achromatic neurons (Pick cells). It also became apparent that cases of clinical PiD with frontal and temporal lobe atrophy may not show the typical Pick bodies on autopsy. Constantinidis and colleagues classified PiD as: (1) with Pick bodies; (2) only with swollen neurons; and (3) only scarring, and neuronal loss. They felt "in spite of the dissimilarities between these forms, considering the absence of sufficient knowledge about pathogenesis, it seems prudent at present to maintain the uniqueness of Pick's entity."

With the development of neuroimaging, frontal and temporal atrophy was demonstrated with increasing frequency in vivo. However, instead of shifting the diagnosis of PiD back to the clinic, more recent studies applied new labels such as dementia of the frontal lobe type, or frontal lobe dementia (FLD) (Brun) as new entities, while reserving the diagnosis of PiD for the pathologist. The groups who described dementia of the frontal lobe type further changed the terminology to frontotemporal degeneration (FTD) (The Lund and Manchester Groups), and frontotemporal lobar degeneration (Snowden et al.). Nevertheless, they acknowledged the clinical syndrome was the same whether or not the histology showed Pick bodies. They estimated the incidence at 20 percent of degenerative dementias.