ABSTRACT
References 688
This chapter has two sections covering the focal dementia syndromes of primary progressive nonfluent aphasia and posterior cortical atrophy.
The term ‘primary progressive aphasia’ (PPA) has been used to encompass all patients with progressive language impairment as the initial feature of a degenerative disorder (Mesulam, 1982; Mesulam, 2001; Mesulam, 2003). There is genetic and pathological overlap with the frontotemporal lobar degeneration (FTLD) spectrum (Neary et al., 1998; Mackenzie and Rademakers, 2007). Although some researchers have classified all language disorders under this one term (Mesulam, 2001; Mesulam et al., 2003), a number of subtypes can be identified (Grossman et al., 2004; Amici et al., 2006; Hodges and Patterson, 2007; Mesulam et al., 2007; Rohrer et al., 2008a). The fluency of speech output forms the basis for a simple clinical descriptive subclassification of PPA i.e. ‘fluent’ and ‘nonfluent’ aphasias. Although fluency is hard to operationalize, nonfluency has generally been used to refer to reduced, effortful or sparse speech. Semantic dementia (SD) is an homogeneous clinicopathological entity with characteristic clinical,
neuropsychological and radiological findings (see Chapter 71, Semantic dementia). SD presents usually with a ‘fluent’ aphasia (Adlam et al., 2006); however two other major PPA syndromes are associated with ‘nonfluent’ language output: these nonfluent disorders, progressive nonfluent aphasia (PNFA) and logopenic/phonological aphasia (LPA), are discussed below. It is unclear if these are the only subtypes of PPA and how this heterogeneous group of conditions maps on to the underlying genetic and pathological causes. While early PNFA can resemble Broca’s aphasia and early LPA may resemble conduction aphasia (Hachisuka et al., 1999; reviewed in Rohrer et al., 2008a), the PPA subtypes do not correspond closely with the acute aphasia syndromes of stroke, due both to differing neuroanatomical patterns of involvement and the progressive nature of the disease. Although there are ‘consensus’ criteria for PNFA and SD (Neary et al., 1998) and other criteria for PPA as a unitary syndrome (Mesulam, 2001; Mesulam, 2003), these are not universally agreed. Descriptive clinical criteria for PNFA, SD and LPA are under revision.
