Dysphagia assessment and intervention for individuals with Huntington’s Disease.

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Speech and Language Therapy
Degree name
Doctor of Philosophy
Publisher
University of Canterbury
Journal Title
Journal ISSN
Volume Title
Language
English
Date
2020
Authors
Burnip, Emma
Abstract

Huntington’s Disease (HD) is a progressive neurodegenerative disease characterised by cognitive, motor and behavioural impairments. Corticobulbar symptoms have been reported in all stages of HD, and aspiration pneumonia associated with swallowing impairment (dysphagia) has been identified as the most common cause of death. Current literature examining interventions to treat or rehabilitate dysphagia in HD is limited; therefore, conventional treatment consists of compensatory techniques to maintain weight and minimise the risk of aspiration. There is emerging multidisciplinary research to suggest that intensive rehabilitation may improve or maintain function of corticospinal symptoms in HD. It has not yet been documented if these changes are evidenced in corticobulbar systems. This research addresses substantial gaps in the literature in respect to evaluation of dysphagia associated with HD, and furthermore evaluates an innovative skill-based dysphagia training protocol in individuals with HD.

The research programme is comprised of three elements. The first was a systematic review of the existing evidence relative to rehabilitation of corticobulbar symptoms associated with HD. Relevant electronic databases were systematically searched for literature related to corticobulbar rehabilitation in HD. The eight studies which met the inclusion criteria were evaluated using standardised critical appraisal tools. The best available evidence was limited by a high risk of bias and a lack of validated and objective outcome measures of corticobulbar symptoms. This systematic review documented a lack of evidence to support the use of rehabilitation to treat corticobulbar symptoms in HD. However, the suggestion of potential positive effects and no adverse effects reported in the limited literature provided justification for further research in this area. For continuity, this systematic review has been included as part of this thesis literature review. The published manuscript can be found in Appendix A.

Although instrumental assessments have been used in a limited number of studies to describe the manifestation of dysphagia in individuals with HD, no research exists regarding the reliability of these measures in this population. The second section of this research was a methodological study which evaluated the reliability and variability of existing measures to assess dysphagia in individuals with HD. Ten individuals diagnosed with symptomatic HD including dysphagia were recruited. Participants underwent instrumental and clinical assessments of swallowing function and biomechanics on three separate occasions over one week. Objective measures of functional swallowing included the Timed Water Swallow Test (TWST) and Test of Masticating and Swallowing Solids (TOMASS). Swallowing biomechanics were measured using manofluoroscopy and ultrasound assessments. Test-retest reliability was evaluated for each measure using Type 3 intraclass correlation coefficient (ICC (3,1)). Results indicated good to excellent reliability (> 0.75) in 5/7 parameters of the functional assessments (TWST/TOMASS) and moderate to excellent reliability (> 0.5) in 4/6 ultrasound measures. Manometric measures produced poor test-retest reliability (< 0.5). Videofluoroscopy measures ranged from poor to moderate reliability (< 0.5 to < 0.75). These data documented mixed reliability for measurement of swallowing in HD. The quantified reliability and variability in this data can be used in selecting and interpreting outcomes in subsequent intervention studies. This research addressed the ongoing need for critical evaluation of the reliability and anticipated variability of swallowing outcome measures in individuals with HD.

The final section of this research programme was an exploratory treatment study which investigated the feasibility and effectiveness of a skill-based swallowing rehabilitation paradigm for individuals with swallowing impairment secondary to HD. Twelve individuals diagnosed with symptomatic HD including dysphagia completed ten sessions of daily skill-

based dysphagia therapy in two weeks using Biofeedback in Strength and Skill Training (BiSSkiT) software and surface electromyography hardware. The software incorporated skill training approaches to improve participant’s volitional control in manipulating the timing and amplitude of the submental muscles involved in swallowing. This intensive intervention, based on the principles of motor learning, aimed to maximise early neural re-organisation reported in HD and enhance cortical modulation to improve the safety and efficiency of swallowing. A within-subject A-B-A study design was utilised to include two-week blocks of no treatment pre-therapy as baseline and post-therapy for retention. Swallowing was evaluated using the TWST, TOMASS, manofluoroscopy, ultrasound and the Swallowing Quality of Life Questionnaire (SWAL-QoL). All participants completed the intervention protocol and improved in task performance over the two-weeks of training. A significant improvement in quality of life was reported post-therapy (p < 0.05) and maintained two-weeks post-treatment. There were significant treatment effects observed as liquid bolus transit times increased and upper oesophageal sphincter (UES) distension decreased post-therapy (p < 0.05). These changes were not maintained during the non-treatment post-therapy period. This study provided preliminary evidence that this intensive skill-based training is a feasible option with no adverse effects in individuals with HD. However, there were limited data to suggest this intervention protocol significantly altered swallowing biomechanics in this patient cohort. This is the first study to evaluate the effectiveness of dysphagia rehabilitation using instrumental swallowing outcomes in HD; therefore, further evidence is required to evaluate treatment protocols according to swallowing characteristics and disease stage.

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