Motor speech disorders in primary progressive aphasia: Clinical presentation and neuroanatomical correlates

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Motor speech disorders (dysarthria, apraxia of speech) are ascribed a high predictive value for the underlying pathology and the course of the disease in primary progressive aphasia (PPA). The overarching goal of the proposed project is to extend knowledge of motor speech disorders in PPA, contributing to a better understanding of this neurodegenerative disease and to further advances in clinical assessment and treatment.The study comprises two major parts. First, we will investigate data from an existing sample of more than 100 patients with PPA of all subtypes from the Research Consortium of Frontotemporal Lobar Degeneration (retrospective study). The database comprises speech recordings as well as study MRIs from each participant. Neurophonetic analyses will be performed with expert raters blinded for PPA subtype (nonfluent, semantic, logopenic variant). The primary objectives of this subproject are the unbiased assessment of the prevalence of motor speech disorders in PPA (dysarthria syndromes, apraxia of speech, mesiofrontal speech motor syndromes) according to standardized criteria, and the identification of their neuroanatomical substrates.Second, we will collect speech data from 40 further patients with different variants of PPA (prospective study). Our aim is to study these patients speech profiles more comprehensively by using a number of well-established instruments specifically developed for the assessment of neurogenic speech disorders, and thereby to implement new diagnostic standards in the clinical assessment of motor speech disorders in PPA. Moreover, the speech data obtained in this way provides the basis for answering further important research questions: For the first time it will be possible to compare the speech profiles of PPA patients with those of patients with dysarthria or apraxia of speech following other degenerative or non-degenerative diseases. For this purpose, we can access an existing database of more than 300 patients with dysarthria and more than 150 patients with apraxia of speech from the Clinical Neuropsychology Research Group (EKN database). Using classificatory approaches, we will also be able to investigate phonetic variables that can contribute to the intricate differential diagnosis of nonfluent and logopenic variant PPA.This study aims at providing, for the first time, an in-depth knowledge of motor speech disorders in German-speaking individuals with PPA.