Introduction

Over the past decade there have been considerable advances in our understanding of the neurodegenerative diseases producing focal cognitive deficits, most commonly referred to collectively as either Pick's disease or, more recently, frontotemporal dementia (FTD). These advances have come from the fields of neuropsychology, neuropsychiatry, neuroimaging and molecular genetics. Unfortunately most non-experts’ ability to follow these developments has been hindered by the confusing plethora of terms which have been used. Central to the problem is a lack of clarity concerning the level of description (clinical syndrome vs clinico-pathological entity vs specific histological diagnosis) and the poor concordance between these levels. In other words, 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. Pick's disease, familial tauopathy, ubiquitininclusion disease), hybrid clinico-pathological entities (frontotemporal dementia), or even specific genetic disorders (e.g. Chromosome 17 linked frontotemporal dementia with parkinsonism). The resurgence of interest in these disorders and the differences in opinion over terminology are well illustrated by the titles of the previous books published on the topic: Pick's Disease and Pick's complex (Kertesz and Munoz, 1998), Frontotemporal Dementia (Pasquier et al., 1996) and Frontotemporal Lobar Degeneration: Frontotemporal Dementia, Progressive Aphasia, Semantic Dementia (Snowden et al., 1996b).

The aims of this introductory chapter are to review the evolution of the terms used to describe this spectrum of disorders, to highlight recent advances and areas of continuing controversy, and to set the scene for the rest of the book. While my own preference has always been to use the term Pick's disease for this group of disorders – partly because this term is more readily understood by carers and parallels our use of the label Alzheimer's disease – the tide of medical opinion turned in favour of FTD in the late 1990s. We have, therefore, adopted this general label within which we distinguish three main clinical variants: frontal or behavioural variant FTD (bv-FTD), semantic dementia (SD) and progressive non-fluent aphasia (PNFA). The sections that follow describe the meandering route that led to the adoption of these terms. The chapter draws heavily upon our own experience of more than 300 patients assessed in Cambridge over the past 15 years.