Lingual Endurance Exercise in Treating Post-Stroke Dysphagia

Implications of Post-Stroke Dysphagia Dysphagia (swallowing impairment) after stroke is common, estimated to affect 78% of patients.1 Dysphagia results in additional negative consequences that complicate patient recovery and increase the risk of developing pulmonary complications (aspiration pneumonia) and may result in suboptimal nutrition. These comorbidities increase cost of care, up to $6,243 on average per patient, placing a burden not only on the individual, but also the healthcare system at large. The effects of dysphagia post-stroke extend beyond physical health concerns and increase the risk of depression, with devastating impacts on quality of life. Given these undesirable and dangerous health consequences, adequate assessment and treatment of swallowing impairments after stroke is a critical component of rehabilitation for this patient population. Limitations to Current Treatment Approaches Current treatment approaches to alleviate dysphagia after stroke, especially in acute and sub-acute phases, have primarily focused on diet modification, compensatory posturing, and providing alternate access to hydration and nutrition. While the goal of these strategies is to improve swallow safety and avoid negative consequences of airway invasion, these techniques can be burdensome to the patient if implemented long-term. Additionally, these approaches do not target rehabilitation of swallowing function, but rather provide a somewhat temporary solution to what is, for many patients, a life-long issue. Available rehabilitative approaches to target improvements in function of oropharyngeal musculature during swallowing include both swallowing exercises (task-specific) and non-swallowing exercises (e.g. tongue exercise), which rely on the principles of transference to improve swallowing function. However, evidence is inconsistent regarding efficacy of these "exercise-based" interventions that target the oropharyngeal musculature, and the scientific validity of these trials varies greatly. Of these non-swallowing exercise approaches, lingual (tongue) exercise has been frequently studied and can be facilitated by medical devices which provide bio-feedback of lingual pressure generative capabilities to the patient and clinician. However, there is little to no evidence that lingual strengthening improves swallow physiology or functional outcomes in post-stroke dysphagia, and a majority of these previous studies lack use of standardized outcomes or randomized controlled trial procedures. Also, lingual strengthening may not induce biological changes to tongue muscle fiber size, as would be expected with a resistance-based exercise program. Despite these mixed findings, lingual strengthening is still routinely to treat post-stroke dysphagia. A major limitation of these current approaches is a sole focus on increasing muscular strength alone without consideration for other aspects of muscle physiology necessary for swallowing, such as endurance. Lingual Endurance Training as an Alternative Approach In this preliminary study, we have proposed to examine the effects of lingual endurance training in individuals with dysphagia after stroke, as an alternative approach to traditional progressive lingual strength training, because this patient group is known to have specific deficits in lingual function after stroke. Both oral and pharyngeal tongue movements are essential for safe and efficient swallowing. Thus, exercise of the lingual musculature is a reasonable goal. However, swallowing is an endurance task; lingual pressures required for swallowing are submaximal, requiring repeated and sustained contraction over the course of a meal. Thus, targeting improvement in lingual endurance over strength alone may provide greater transferrable benefit to daily swallowing tasks. However, there are currently no randomized controlled trials investigating efficacy of lingual endurance training as a treatment for dysphagia in any patient population. As such, this proposed preliminary trial is essential to gathering the necessary pilot evidence regarding whether lingual endurance training is feasible and effective as an alternative approach to dysphagia rehabilitation for individuals with swallowing impairments after stroke. The long-term goal of this proposed work is to develop improved, evidence-based protocols for lingual exercise training for individuals with dysphagia after stroke. Ultimately, the results of this proposed pilot will be highly significant in creating movement towards more specific and evidence-based approaches for this unique patient group, who currently have very few rehabilitative options available. In this initial trial, we will assess if lingual endurance training will be feasible (Aim 1) and effective (Aim 2) for improving swallowing function in post-stroke dysphagia.