3 results
18 - Semantic dementia
- Edited by Bruce L. Miller, University of California, San Francisco, Bradley F. Boeve, Mayo Foundation, Minnesota
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- Book:
- The Behavioral Neurology of Dementia
- Published online:
- 31 July 2009
- Print publication:
- 28 May 2009, pp 264-278
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Summary
Introduction
Semantic dementia (SD; also known as progressive fluent aphasia) is regarded as a part of the spectrum of non-Alzheimer dementias that produce selective atrophy of the anterior temporal and/or orbitomedial frontal lobes; these conditions are referred to collectively as either the frontotemporal dementias (FTD) or frontotemporal lobar degeneration (FTLD) (Neary,1994; Neary et al., 1998). Although previously thought to be rare, FTD in fact has about the same prevalence as Alzheimer's disease (AD) below the age of 65 (Ratnavalli et al., 2002). Three clinical presentations of FTD are commonly described: a behavioral variant (bv-FTD), and two language variants, SD and progressive non-fluent aphasia (PNFA) (Hodges and Miller, 2001a,b). Since the mid 1990s, research on SD has produced a great deal of information about the clinical and neuropsychological features, progression, anatomy and neuropathology of the condition, which we attempt to review and synthesize here.
Early history
Although the term “semantic dementia” is recent (Snowden et al., 1989), the syndrome has been recognized under different labels for over a century. Between 1892 and 1904, Arnold Pick (1892, 1904) reported a series of remarkable cases characterized by progressive amnesic aphasia and changes in behavior; at autopsy these patients had marked atrophy of the left temporal lobe. Pick was perhaps the first neuroscientist to draw attention to the fact that progressive brain atrophy may lead to focal symptoms.
Section 3 - Slowly progressive dementias
- Edited by Bruce L. Miller, University of California, San Francisco, Bradley F. Boeve, Mayo Foundation, Minnesota
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- Book:
- The Behavioral Neurology of Dementia
- Published online:
- 31 July 2009
- Print publication:
- 28 May 2009, pp -
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7 - The histopathology of frontotemporal dementia
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- By R. Rhys Davies, University Department of Clinical, John H. Xuereb, Division of Molecular Histopathology
- Edited by John R. Hodges, University of Cambridge
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- Book:
- Frontotemporal Dementia Syndromes
- Published online:
- 05 August 2016
- Print publication:
- 08 November 2007, pp 161-207
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Summary
Introduction
The emergence of frontotemporal dementia (FTD) as a clinical entity (McKhann et al., 2001; Neary et al., 1998) has provided impetus to disciplines ranging from genetics to neuropsychology (Hodges and Miller, 2001a, 2001b). The concept of FTD,1 however, is fundamentally heterogeneous. Histopathological characteristics form the hub of this heterogeneity, relating on the one hand to the varied clinical manifestations of FTD and, on the other, to findings in the burgeoning field of FTD genetics.
The chapter begins with an historical introduction to the concept of FTD followed by an outline of the various histopathological subtypes. After briefly describing the clinical spectrum of FTD we discuss clinico-pathological insights that have been acquired as post-mortem collections, instigated more than a decade ago, have matured. We emphasise the feasibility of predicting pathological subtype during life, at least in a proportion of FTD cases. We then explore the complex relationship between the genetics and histopathology of FTD. We conclude with the unifying perspective that FTD may be understood as pathology affecting one or more neural systems.
Historical background
In 1907 Alois Alzheimer described the neuropathological findings in a woman who died at the age of 56 after a 5-year illness consisting of cognitive impairment and psychiatric disturbance; silver-staining plaques and tangles were seen on microscopic examination (Alzheimer, 1907). Although similar appearances had previously been documented in older patients, the term “Alzheimer's disease” (AD) began to be used for this combination of plaques and tangles from 1910 (Kraepelin, 1910). Alzheimer's disease, formally diagnosed at post-mortem examination, now encompasses both senile and pre-senile cases. It is so common, accounting for two-thirds of dementia cases among those aged older than 65 (perhaps half a million cases in the UK), that its particular features pervade our concepts of dementia in general (Bachman et al., 1992). For instance, the stipulation that dementia should only be diagnosed in patients above a certain age in whom memory impairment is detected derives from the typical presentation of AD with amnesia in the elderly (DSM–IV–TR; American Psychiatric Association, 2000). Indeed, about 90% of patients manifesting such features have the neuropathological characteristics listed by Alzheimer (Tierney et al., 1988).