Audiology and Speech Pathology - Theses
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ItemMotor speech phenotype of Huntington’s disease: A potential clinical marker in the premanifest phase( 2021)Huntington’s disease (HD) is an inherited neurodegenerative condition caused by a mutation in the HTT gene coding for the protein Huntingtin. The autosomal dominant inheritance nature of HD makes it amenable to diagnostic and predictive genetic testing. HD is characterised by movement disorder, cognitive and psychiatric symptoms. A formal diagnosis of manifest HD is indicated by the phenotypic appearance of unequivocal movement disorder in carriers of expanded HTT gene. Prior to diagnosis of manifest HD, carriers of the expanded HD gene may show subtle changes in their fine motor skills, cognition, behaviour, and speech. The premanifest phase of HD (PreHD) may be an optimal time for introduction of disease-modifying drug trials, based on an assumption that the brain is most receptive to therapeutic changes in that period. Various intervention methods are in development, but one of the challenges in clinical trials, however, is the lack of easily accessible, sensitive and measurable biomarkers to improve onset detection accuracy, provide routine monitoring of disease progression, and evaluate intervention efficacy. The thesis explored the use of acoustic speech as a potential biomarker of HD, by (i) identifying speech symptoms in the premanifest and manifest phases of HD, (ii) examining speech stimuli and digital speech metrics that are sensitive in detecting speech changes in people carrying the expanded HD gene, and (iii) evaluating the reliability and speech metrics of speech across multiple assessment intervals. Speech was analysed perceptually and objectively, and measures of articulatory agility, voice quality, and prosody (speech-timing) were extracted and compared between people with premanifest HD, manifest HD and healthy controls. Speech outcomes were correlated to other clinical measures of motor function, fine motor performance, cognitive abilities and disease burden. A 6-month longitudinal speech investigation was also conducted to evaluate the reliability and stability of speech in PreHD. Findings from experimental studies in the thesis indicated speech differences between PreHD and control groups were audible to expert listeners (i.e., speech pathologists) using perceptual assessment of speech (Chapter 4). Objective acoustic analysis revealed speech differences on measures of articulatory agility and speech-timing between PreHD and healthy controls, but these differences are only observed in speech tasks that required a higher level of cognitive load and motor effort (Chapter 5). Speech tasks and speech metrics shown to be sensitive, reliable, and stable in PreHD and healthy controls were identified in the final chapter of this thesis (Chapter 6). Overall, these studies have explored the potential for acoustic speech measures to be utilised in clinical settings as behavioural markers of disease. The validation of speech as markers requires further research in the field, however, the thesis has provided some data on using speech to monitor disease progression and evaluate treatment efficacy in premanifest and manifest HD.