Apraxia of speech in degenerative neurologic disease

Background: Only a limited number of case reports or case series have provided unequivocal evidence that apraxia of speech (AOS) can be the first or predominant sign of neurodegenerative disease. This may reflect a very low frequency of occurrence but may also reflect a failure in many studies to identify AOS or distinguish it from the diagnosis of primary progressive aphasia (PPA). The distinction may be important to clinical neurological localisation and diagnosis, prognosis, management, and histopathology. Aims: To describe the demographic characteristics, presenting complaints, perceptual attributes, associated speech-language and related clinical findings, neuroimaging findings, and clinical neurological diagnoses for a large group of patients with AOS due to degenerative neurologic disease. Methods & Procedures: Retrospective review of patients seen between 1985 and 2004, who had AOS that was never less severe than any aphasia that might have been present and whose neurologic evaluation concluded that the cause was degenerative. Outcomes & Results: A total of 80 patients met inclusion criteria. Of these patients, 61% were men. Average age at initial evaluation was 69 years (range=36-86 years). Speech-language difficulty was the first symptom to emerge in 80% and the only patient complaint at the time of initial evaluation in 56%. Average duration of symptoms at initial evaluation was 29 months. Aphasia and dysarthria were unequivocally present in 49% and 50% of the sample, respectively. Of the 80 patients with AOS, 11% had neither aphasia nor dysarthria. When abnormal, neuroimaging often identified left or left<right hemisphere abnormalities. Of these patients, 44% received purely descriptive clinical neurologic diagnoses that were largely determined by speech-language findings; an additional 18% received diagnoses related to focal/asymmetric cortical atrophy syndromes that localised to the left hemisphere; 29% received diagnoses of diseases with prominent motor manifestations, most often corticobasal degeneration, progressive supranuclear palsy, or motor neuron disease. Conclusions: AOS can be the first and most prominent manifestation of neurodegenerative disease. It often co-occurs with aphasia and/or dysarthria, but it can be the only speech-language disorder. It does not appear to be associated with any single neurologic disease but specific neurologic diagnoses, when they are possible, tend to reflect conditions with prominent motor manifestations. It is important to distinguish primary progressive AOS from PPA.