Swallowing is a sophisticated activity that requires both voluntary and involuntary coordination of motor and sensory mechanisms of the oropharynx. Epidemiologically around 50 percent of stroke survivors have either suffered from dysphagia at the onset of their strokes and recovered, or have been chronically dealing with complications of dysphagia. Swallowing assessment is one of the most important components of the initial survey of stroke patients upon their arrival at the emergency department, simply because it can lead to aspiration pneumonia (Ap), and in most cases ordering NPO is a wise choice. But, what are the underlying mechanisms of dysphagia and why is it a prevalent post stroke issue?
Mechanism of Swallowing :
Swallowing requires both sensory and motor input/output and cranial nerves play the main role in this process, but when the definitive diagnosis of stroke is reached, the involvement of these nerves become irrelevant and the and the brain pathologies could be linked to the swallowing abnormalities.
Originally, the main regions highly involved in regulation of swallowing was thought to be the brain stem and the afferent and efferent cranial nerve nuclei innervating muscles of mastication. Previous studies have all shown a direct correlation between lesions in medial and lateral medulla oblongata and swallowing complications (González-Fernández, Ottenstein, Atanelov, & Christian, 2013) leaving no doubt that involuntary and reflexive portions of swallowing is controlled by the brain stem. But the prevalence of dysphagia in stroke patients and the advent of neuroimaging techniques have also revealed the role of cortical and subcortical regions highly involved in regulation of swallowing mechanisms (Dehaghani, Yadegari, Asgari, Chitsaz, & Karami, 2016). Motor and sensory cortices, prefrontal area and basal ganglia are all important regions processing and coordinating and sequencing the muscles of mastication.
Bedside Assessment, and Management of Dysphagia
Ordering NPO could be a life saving step in acute stroke, and usually the bedside swallowing assessments must be done within the first few hours of onset by speech language pathologists (SLP) or nurses. As most stroke patients improve generally with their motor functions within the first few months swallowing could improve too. Thickened fluid, and pureed diet in conjunction with SLP rehab could also improve outcome. The problem arises after years of swallowing problems (mainly in stroke, and other neurodegenerative disease of aging), these patients usually end up with enteral feeding (PEGs and tube feeding) or develop more complications such as aspiration pneumonia (Cohen et al., 2016).