About 25 years ago, I evaluated a 71-year-old woman who had a neurologic consultation to assess her two-and-a-half year history of speech difficulty. At that time, she had an apraxia of speech without any other neurological problems. During the next seven years she taught me and my colleagues a great deal about the nature of her speech problem and about the other neurological signs that eventually emerged during the course of her disease. There was no accepted label for her problem at the time, but she and others with similar speech difficulty helped seed an accumulation of observations that defined a clinical syndrome that we now call primary progressive apraxia of speech. What those individuals taught us has yielded several facts and here are a few:
- Apraxia of speech (AOS) can be the only/most salient clinical feature of neurodegenerative disease. AOS can be the only observable deficit for a number of years. When this occurs, the appropriate diagnosis is primary progressive apraxia of speech (PPAOS). It is sometimes misdiagnosed as primary progressive aphasia (PPA).
- Neuroimaging studies of people with PPAOS usually reveal left, or left greater than right, hemisphere abnormalities in the mid and superior premotor cortex and supplementary motor areas. This differs from the localization associated with variants of PPA. Neuroimaging in both PPAOS and PPA may be normal early in the disease course.
- PPAOS eventually tends to be associated with conditions that have prominent motor rather than cognitive deficits, such as progressive supranuclear palsy syndrome or corticobasal syndrome. Some affected people also develop aphasia.
- The neurodegenerative nature of PPAOS does not preclude management, including speech therapy to improve or maintain speech. The need for augmentative-alternative means of communication must be anticipated and needs to account for the possible emergence of language impairment and limb-motor and visual deficits.
- PPAOS tends to predict underlying pathology consistent with tauopathy and with progressive supranuclear palsy or corticobasal degeneration. This association – especially if accurate clinical diagnosis can be made early – will be very important when disease-modifying agents for tauopathies become available.
PPAOS is not often encountered by speech-language pathologists in most clinical settings, but the fact that it is an uncommon problem makes recognizing its identifying features all the more critical. It ends the uncertainty experienced by affected individuals who have been seeking a medical diagnosis for their unexplained, progressing speech difficulty and it is key to the subsequent provision of information, counseling, support, and therapy needed for optimal patient care.