Impacts of skill training on swallowing and quality of life in patients with motor neurone disease

Abstract

Motor neurone disease (MND) is a neurodegenerative disease with reported incidence between 1.68 and 2.08 per 100,000 (A Chio et al., 2013; Marin et al., 2017) and prevalence of 5.40 per 100,000 (A Chio et al., 2013). The defining symptoms of MND are loss of voluntary control of muscle movement, spasticity and hyperreflexia due to degeneration of upper motor neurons, and flaccidity, atrophy and fasciculations due to degeneration of lower motor neurons. These symptoms can affect the muscles of deglutition, resulting in oropharyngeal dysphagia. Patients with MND are not often offered dysphagia treatment due to a historical belief that exercise would result in muscular fatigue and increased rate of degeneration (Plowman, 2015). However, recent research demonstrates that low to moderate intensity exercise may be beneficial for patients with MND (Carreras et al., 2010; Plowman, 2015). Additional research is necessary to determine appropriate treatment modalities to improve swallowing outcomes in this population. The research presented in this thesis investigated the effects of skill training on swallowing and quality of life outcomes in patients with MND. This programme of research involves a methodological study investigating quantification of fatigue during exercise of bulbar muscles and two exploratory studies that investigated the effects of skill training for swallowing.

Study one investigated the potential for using surface electromyography (sEMG) as a method of quantifying fatigue of bulbar muscles during a lingual pressure endurance task. It is known that as muscles become fatigued, additional motor units are recruited, firing frequency increases and discharges are synchronised for sustained power generation (Chang, Chablat, Bennis, & Ma, 2016). However, it is unknown whether the smoothed data from sEMG of the submental muscles can be used during a lingual pressure task to indicate degree of muscular fatigue. Twenty-four healthy participants completed a lingual endurance task with sEMG placed over the submental muscles. Results demonstrated fatigue over the task, represented by a gradual decline in endurance time. However, there was no significant difference in average sEMG output across sessions, indicating that sEMG of the submental muscles, as used in this study, is not an appropriate method of quantifying fatigue during a lingual pressure task.

The second and third studies were exploratory studies that first assessed the feasibility of a skill training protocol in patients with MND and then assessed the effect of the treatment on biomechanical, functional and quality of life outcomes. The aim of the pilot study was to determine whether further research was possible within the New Zealand context and to refine the methodology of the treatment study. Five participants underwent a four-week skill training protocol with a four-week no contact periods pre-treatment (baseline) and post- treatment (retention). The skill training protocol consisted of 80 swallows per session using the Biofeedback in Strength and Skill Training (BiSSKiT) software. BiSSkiT uses surface electromyography (sEMG) for visualisation of muscle activity to enhance conscious control of swallowing. There were no drop outs and all participants were able to follow instructions to complete the treatment task. Following treatment, an improvement in functional swallowing was observed for the patients with mild to moderate dysphagia. This improvement was demonstrated through increased volume swallowed per second, increased swallowing efficiency and decreased time per swallow when consuming 150 mL of water in the Timed Water Swallow Test (TWST). These findings indicated that further research was warranted.

The treatment study followed the pilot study and investigated additional outcome measures including biomechanical changes to swallowing. For the treatment study, 27 patients with MND were recruited. From these participants, 19 completed two weeks of daily skill training using the BiSSkiT software with a two-week baseline and two-week retention period. Quality of life was measured through the Swallowing Quality of Life Questionnaire (Swal-QOL), functional swallowing assessed through the TWST and the Test of Masticating and Swallowing Solids (TOMASS). Additionally, instrumental assessments (ultrasound [US], videofluoroscopy [VF] and high resolution impedance manometry [HRIM]) were included to assess swallowing biomechanics. Following treatment, timing (p < .01) and amplitude (p = .04) errors during the skilled task decreased, total symptom frequency measured by the Swal- QOL improved (p = .02) and oropharyngeal transit time decreased for puree (p = .01) but increased for water (p = .02). Hyoid displacement on VF increased over the retention period but not the treatment period for water (p = .04) and puree (p = .01). Although there was evidence of improvements in quality of life and swallowing biomechanics, there were no significant differences observed in functional swallowing outcomes. This research demonstrates that participants with MND are able to participate in swallowing skill training and improve at the task with no evidence of adverse effects. Changes in quality of life and swallowing biomechanics were observed following two weeks of treatment; however, there was no transfer to functional tasks. This suggests two weeks of treatment is not sufficient for functional improvement but may have facilitated maintenance of function and highlights the need for future research.

Skill training is a developing area of treatment for dysphagia. This research was the first to investigate the use of skill training to improve pharyngeal swallowing for patients with MND. Results from these studies add to the emerging literature that demonstrates the need for alternative options to traditional strength based treatment for patients with dysphagia.