Pick’s disease: its relationship to progressive aphasia, semantic dementia and frontotemporal dementia

References 654 Considerable advances continue to be made in our understanding of the group of neurodegenerative diseases that present with focal cognitive deficits arising from circumscribed pathology of the frontal and/or temporal lobes, most commonly referred to collectively as Pick’s disease (PiD) or frontotemporal dementia (FTD). However, the literature on these conditions is filled with a confusing plethora of terms, which can make these developments difficult to follow for the nonexpert. Central to the problem is a lack of clarity as to the intended level of description (clinical syndrome versus clinicopathological entity versus specific histological diagnosis) and a lack of concordance between these levels. For example, while some labels denote a clinical syndrome without specific histological implications (e.g. progressive aphasia, semantic dementia or dementia of frontal type), others denote specific neuropathological entities (e.g. PiD or familial tauopathy), hybrid clinicopathological entities (e.g. FTD), or even specific genetic disorders (e.g. FTD with parkinsonism linked to chromosome 17). Recent differences in opinion over terminology are well illustrated by the titles of the following books, all published in the last decade: Pick’s disease and Pick complex (Kertesz and Munoz, 1998), Frontotemporal dementia (Pasquier et al., 1996), Frontotemporal lobar degeneration: frontotemporal dementia, progressive aphasia, semantic dementia (Snowden et al., 1996) and Frontotemporal dementia syndromes (Hodges, 2007). This lack of clarity is acknowledged, and efforts to rationalize terminology and achieve clinicopathological and nosological consensus have been made (Brun et al., 1994; Neary et al., 1998; McKhann et al., 2001). Even at a recent meeting of experts, agreement over terms was far from universal (Kertesz et al., 2003b).