Progressive apraxia of speech and primary progressive aphasias

Apraxia of speech (AOS) is a motor disorder that occurs as a result of impairment in the planning or programming of movements for speech production. It is typically associated with cerebrovascular events, although it can also occur in the context of neurodegeneration where its importance has typically been deemphasized to "just a component of a presenting syndrome." Primary progressive aphasia (PPA) is such a syndrome in which AOS coexists with other linguistic defi cits, typically agrammatic aphasia. Recently, however, AOS has been demonstrated to occur in a pure or isolated form, known as primary progressive apraxia of speech (PPAOS), reaffi rming the importance of neurodegenerative AOS. Furthermore, anatomic and pathologic associations differ between AOS-dominant syndromes and PPA variants. Understanding the relationship between AOS-dominant variants, including PPAOS and PPA, and their relationship to movement disorders including corticobasal degeneration and progressive supranuclear palsy, is important and will be the focus of this chapter.