ABSTRACT
References 677
Semantic dementia is a disorder of conceptual knowledge, resulting from temporal lobe neurodegeneration (Snowden et al. 1989; Hodges et al. 1992). It is one of the distinct clinical syndromes, along with the behavioural disorder of frontotemporal dementia (FTD) and expressive language disorder of progressive non-fluent aphasia (PNFA), encompassed under the umbrella of frontotemporal lobar degeneration (FTLD) (Table 71.1) (Neary et al., 1998). Patients with semantic dementia lose the ability to name and understand words, to recognize faces, and to understand the significance of objects, non-verbal sounds, tastes and smells (Snowden et al., 1996; Bozeat et al., 2000). Nonsemantic aspects of cognition are largely preserved. It is the dramatic, yet selective nature of the semantic disorder, together with characteristic behavioural alterations, that distinguishes semantic dementia from Alzheimer’s disease (AD). Although relatively rare, recognition of the disorder is important because of its distinct implications for management. Moreover, in recent years it has attracted considerable academic interest because of its potential to shed light on the organization and neural basis of semantic memory. From a neurobiological perspective, a central interest is the relationship between semantic dementia and other forms of FTLD.
