Acquired brain injury (ABI) is an umbrella term used to describe damage that occurs to the brain after birth that is not associated with a hereditary or progressive disease. It can be characterised by traumatic brain injury (TBI) and non-traumatic brain injury (nTBI). Traumatic brain injury refers to damage to the brain from an external force such as a blunt force object, car accident or fall. In contrast, nTBI arises from internal damage to the brain such as stroke, a brain tumour or asphyxiation.
The incidence of ABI can vary across the lifespan. It is estimated that around 348, 934 patients per year are admitted to hospital with an acquired brain injury (Tenant, 2018) with roughly 40,000 of these cases occur in children (Menon, 2018). In older adults, ABI is typically linked to cerebrovascular accidents such as stroke whereas in teenagers and younger adults, traumatic brain injury from external trauma and car accidents are more common (Turner-Stokes, 2015). Acquired brain injury in infants and young children typically arises from a range of causes including birth trauma, brain tumours and infection (Middleton, 2001). In approximately 8% of children diagnosed with cerebral palsy (CP) this is secondary to postneonatal head injury or infection (Vitrikas, 2020).
The management of ABI also differs across the lifespan. Children are far more likely to be discharged to their home environment following a brain injury than adults (Chan, 2016) and typically have less access to specialist therapeutic services to support the rehabilitation of a wide range of morbidities which can occur following ABI (Hayes, 2016).
Dysphagia (swallowing difficulty) is one of these possible morbidities, with studies recording dysphagia in up to 93% of people with ABI (Hansen, 2008). Although the severity of dysphagia varies, dysphagia in any form can cause psychological and physical consequences such as anxiety, embarrassment, social isolation and increased risks of pneumonia, dehydration and mortality, (Moloney & Walshe, 2018), (Ickenstein et al., 2005). Weight loss and poor nutrition is another possible complication of dysphagia, especially due to the increased metabolic demands placed on the body following a brain injury (Foley, 2008). This is especially pertinent in children, where poor nutrition can lead to faltering growth, impacting on overall physical and cognitive development (Morgan, 2009).
Typically management of dysphagia, in both adults and children, has focused increasing the safety of swallowing via indirect strategies such as such as thickened fluids, positional support or supplementary feeding methods such as percutaneous endoscopic gastrostomy (PEG). Although these management strategies aim to reduce the risk of aspiration pneumonia, they do not change the underlying swallowing function and do little to combat the psychosocial isolation someone with dysphagia may experience. Eating and drinking often forms a significant emotional and social part of someone’s everyday life and texture modification or supplementary tube feeding can significantly impact this social participation. The need to consider direct rehabilitation options in order to improve the swallowing physiology is therefore vital in order to make life changing medical, psychosocial and economic differences.
In the 1980’s direct rehabilitation strategies to restore physiological functioning of swallowing in adult populations emerged (Ylvisaker et al., 1985). Initial approaches used sensory based stimulation methods such as ‘thermal tactile stimulation’ which involves stimulating the anterior faucial pillars of the oral cavity with a cold probe. The aim of this being to increase the sensitivity of the oral cavity and therefore stimulate a timely swallow trigger (Logemann, 1986). Rehabilitation then progressed onto using specific exercises to target weak oro-pharyngeal musculature, for example, the ‘Effortful Swallow’ was used to improve contact between the base of tongue and posterior pharyngeal wall (Logemann, 1991), the ‘Mendelson manoeuvre’ to improve laryngeal elevation (Mendelsohn et al, 1987) and the ‘head lift’ to improve hyoid displacement (Shaker et al., 1997). More recently, rehabilitation has focussed on re-acquiring the ‘skill’ of swallowing through specific exercise programmes (Athukorala et al., 2014). Skill in this context refers to an ability to regulate the precision and timing of swallowing in relation to a bolus.
Strategies to improve patient understanding, engagement and performance when performing these exercises have since been introduced. These strategies often use electronic devices in order to provide online biofeedback regarding the accuracy of the exercises being performed. An example of a biofeedback system in adult rehabilitation practice is ‘surface electromyography’ (sEMG) (Merletti, 2016). This measures the timing and force of muscle contraction using electrodes placed on a selected area and provides a visual, graphical representation of those measures. The visual feedback can act as a reference point during therapy for patients to measure their performance by. Another area of development involving technology, is neuromuscular electrical stimulation (NMES). This can be used in isolation or combined with exercises to electrically stimulate the oropharyngeal muscles. Electrodes are placed at specific points around the lower jaw and neck to stimulate the targeted pharyngeal musculature and strengthen the directed muscles. There is evidence to suggest that combining oro-pharyngeal exercises with biofeedback and/or electrical stimulation increases motivation, improves accuracy of movement and generates better functional outcomes for patients (Archer, 2020), (Crary, Carnaby, Griher, & Helseth, 2004), (Huckabee et al., 2016), (Steele, 2004), (Sun, 2013). Despite the therapeutic advances in adult populations described above, there remains a generalised lack of research into the physical, cognitive and emotional rehabilitation of children post brain injury (Chan, 2016). In dysphagia practice, young people continue to rely on indirect, conservative feeding strategies to manage their dysphagia (Dodrill & Gosa, 2015). Expert opinion guidelines for management of paediatric acquired brain injury still recommend the use of rehabilitative swallowing exercises from a theoretical perspective but recognise the need for specific research in this area (Morgan et al., 2017). One possible reason for this, is that developing therapeutic protocols in paediatric populations is more challenging given the overall incidence of ABI is smaller. Whilst it is not always possible to make direct translations from approaches used in adult populations to that of paediatrics (Forsyth, 2010), there is evidence in other therapeutic areas, of developing paediatric interventions from the adult literature. For example, the use of ‘functional electrical stimulation’ in upper limb therapy has been applied in the treatment of children with CP based on research from adult ABI population (Garzon, 2018). Having a clear understanding of the scope and effectiveness of interventions described in both the adult and paediatric literature is therefore a key first step in developing the evidence base in paediatrics.
The aim of this paper, therefore, is to outline the published literature on exercise-based treatment methods used in the rehabilitation of dysphagia secondary to an acquired brain injury across the lifespan. This will be used to identify intervention differences and gaps between adult and paediatric populations and guide discussions with clinicians about which interventions might be appropriate for further trials in paediatrics. For the purposes of this study cerebral palsy is included in the definition of acquired brain injury.
Developing the research question:
Previous clinical guideline papers have highlighted the lack of available literature on the rehabilitation of swallowing following brain injury in children (Morgan, 2017). Experience from clinical practice highlights that this can be a source of frustration for parents and families who frequently ask if there are any rehabilitation strategies to help resolve their child’s swallowing impairment because they may have heard or read about available treatments in adults. It was therefore felt important to include both adult and paediatric literature in this review to enable the research gaps to be formally acknowledged and reported.
The research question posed by the researchers following on from this decision was ‘What rehabilitation options are available for people with dysphagia secondary to ABI?’ This question was used to conduct a pilot literature search to gain up to date information about treatment methods available in both adult and paediatric populations. The search highlighted that treatment options for dysphagia rehabilitation could be separated into several groups: Surgical, pharmaceutical, cortical and peripheral stimulation, alternative therapies and direct oro-pharyngeal exercises. Given the breadth of treatment options, the question was subsequently redefined to explore one of these treatment groups: Oro-pharyngeal exercises. The use of exercises in the rehabilitation of paediatric dysphagia recognised as a research priority by The Royal College of Speech and Language Therapists (RCSLT) and the National Institute of Health Research (NIHR), 2018 and their use has also been recommended in paediatric brain injury therapeutic guidelines based on expert consensus opinion (Morgan, 2017).
Therefore the primary research question posed by the researcher is:
What direct oro-pharyngeal exercise protocols are available for adults/children with dysphagia post acquired brain injury?