Semantic dementia and Alzheimer's disease: Clinical differences in speech-language pathology
Perspectives on Gerontology
Speech-language pathologists working in the field of geriatrics need to be aware of two variants of primary progressive
aphasia (PPA). The nonfluent type is characterized by dissolution of phonology (spoken word form) and syntax (grammar),
in the absence of any cognitive and semantlc deficits at the time of onset (Mesulam, 1982; 2001; Thompson. Ballard, Tait, Mesulam, & Weintraub, 1992; Rogers & Alarcon, 1998. Kertesz & Orange, 2000). The nonfluent type has retained the original
name of PPA. The other type, termed semantic dementia (SD), is a fluent variant with initially intact cognition and progressively diminishing receptive and expressive vocabulary due to semantic loss (Hodges, Patterson, Oxbury, & Funnell, 1992; Breedin, Saffran, & Coslett, 1994; Hodges & Patterson, 1996). Both SD and nonfluent PPA are associated with a larger group of disorders resulting from a dysfunction to the fronto-temporal lobes of the brain, termed accordingly the fronto-temporal dementias (FTD).
Jokel R. & Rochon E.A.