A traumatic brain injury (TBI) can lead to problems with cognition, behavior, and physical functions, with each domain playing a crucial role in swallowing. Normal control of swallowing requires appropriate integration of the brainstem, basal ganglia, thalamus, limbic system, cerebellum, and the motor and sensory nerves ( Fig. 31.1 ). These systems work together to control afferent/efferent, anticipatory/preparatory, and voluntary/automatic processes in the more than 30 muscles involved in swallowing cortices ( Fig. 31.2 ). 1 , One of the most common challenges faced by clinicians in TBI patients is dysphagia.
Dysphagia
Dysphagia is difficulty in swallowing because of congenital or structural abnormalities or impairment in neuromuscular control. Dysphagia caused by neurologic dysfunction (such as after TBI) may result from abnormalities in any of the four phases of swallowing: oral preparatory phase, oral phase, pharyngeal phase, or esophageal phase.
Risk factors that put patients at highest risk of aspiration pneumonia
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Glasgow Coma Scale (GCS) score of less than 9
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Rancho Los Amigos Scale (RLAS) score less than 3
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No oral intake on admission
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Intubation
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Tracheostomy
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Oropharyngeal spasticity
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Myoclonus
As such, careful evaluation for dysphagia needs to be a key component of acute rehabilitation for patients after a neurological dysfunction, because impaired swallowing may result in aspiration, decreased epiglottis movement, or impaired laryngeal elevation. Swallowing characteristics of patients with dysphagia after TBI were comparable to patients with dysphagia after stroke in videofluoroscopic swallowing study (VFSS), with findings of aspiration or penetration, decreased laryngeal elevation, and reduced epiglottis inversion.
Without proper attention and intervention, patients are at risk for dehydration, malnutrition, weight loss, aspiration, and pneumonia. These consequences can lead to prolonged hospitalization and worsened functional status limiting improvement in the acute period after injury. There remains limited research and development of dysphagia treatment protocols, leading to a high level of variability based on provider preference and background.
Summary
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A TBI will lead to problems with cognition, behavior, and physical functions, which all play a crucial role in swallowing.
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Three factors putting patients at highest risk of aspiration pneumonia: GCS score of less than 9, RLAS score less than 3, and no oral intake on admission.
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Other risk factors for dysphagia after TBI include intubation, tracheostomy, oropharyngeal spasticity, or myoclonus.
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Consequences of undiagnosed dysphagia include dehydration, malnutrition, weight loss, aspiration, and pneumonia, which can lead to worsened functional status and prolonged hospitalizations.
Four phases of swallowing
Normal swallowing in humans was first described with a three-stage sequential model that depended on the position of the bolus: the oral, pharyngeal, and esophageal stages. Known as the Process Model , it describes the mechanism of eating and swallowing solid food. , Because this model does not describe the mechanism of swallowing liquid food, a four-phase model was developed to describe the biomechanics and bolus movement during command swallows of liquids. In the four-phase model, the oral stage was subdivided into the oral preparatory stage and the oral propulsive stage, whereas the pharyngeal stage and the esophageal stage remain the same. During swallowing, the bolus of food or liquid is manipulated by muscles and reflexes involving the nasopharynx, oropharynx, and hypopharynx.
Oral preparatory stage
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This stage starts when liquid bolus is in the anterior part of mouth floor or on the tongue surface enclosed by the hard palate and upper dental arch.
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The oral cavity is sealed posteriorly by the soft palate and tongue to prevent the liquid bolus from leaking into the oropharynx before the swallow.
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An imperfect seal may allow leakage of liquid into the pharynx, which becomes more common with aging.
Oral propulsive stage
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This stage helps to prepare the bolus; it includes mastication of the bolus and the use of tongue movements to help with positioning.
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The soft palate moves forward to close the oral cavity.
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The tongue closes the anterior portion of the oral cavity and moves the bolus toward the oropharynx.
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Velopharyngeal closure is needed to protect the bolus from entering the nasopharynx.
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Problems with this phase result in drooling, pocketing, and possibly a compensatory head tilt.
Pharyngeal stage
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This is a reflexive coordination of events that result in the bolus being moved from the mouth to the esophagus.
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The risk of aspiration is greatest in this phase despite a coordinated inhibition of breathing to prevent aspiration.
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During this phase, the soft palate propels the bolus toward the esophagus, accompanied by elevation of the larynx with anterior hyoid bone movement to help with epiglottis placement over the entry of the airway.
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The true and false vocal cords are adducted to provide additional airway protection.
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A coordinated constriction of the pharynx and relaxation of the cricopharynx or upper esophageal sphincter help the bolus to enter the esophagus smoothly.
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Problems with this phase can result in coughing, choking, a sensation that food is stuck, or aspiration.
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A systemic review of physiological factors related to aspiration in oropharyngeal dysphagia found measurement of tongue strength, hyoid movement, bolus time in the pharynx while the larynx stays open, respiratory rate, and respiratory swallow phasing help determine aspiration risks.
Esophageal stage
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Also reflexive in nature, this is the longest phase of swallowing.
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The bolus passes from the pharynx to the esophagus and eventually arrives in the stomach.
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Relaxation of the gastroesophageal sphincter is required even if the patient is in a seated or upright position.
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Problems with this phase can lead to acid reflux symptoms such as frequent burping, throat irritation, or the sensation that food is sticking.
Summary
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Four stages of swallowing: Oral preparatory, oral propulsive, pharyngeal, and esophageal
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Oral preparatory stage: Bolus is in anterior portion of mouth. An imperfect seal will lead to leakage into pharynx, which is more common in aging.
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Oral propulsive: Bolus is positioned and moved toward oropharynx. Problems can result in drooling, pocketing, and head tilt.
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Pharyngeal phase: Greatest risk of aspiration is in this phase and requires a coordinated inhibition of breathing to prevent aspiration. Problems in this phase result in coughing, choking, aspiration, or sensation that food is stuck.
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Esophageal phase: Longest phase of swallowing. Problems can lead to acid reflux symptoms such as frequent burping, throat irritation, or sensation that food is sticking.
Evaluation
Many bedside and instrumental tools have been developed for the diagnosis and treatment of dysphagia with varying degrees of sensitivity and specificity. Testing ranges from dysphagia screening to diagnostic evaluation of dysphagia using bedside and instrumental assessment. Screening is used to assess the possibility of aspiration (overt or silent) and risk for complications.
Screening tools
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Burke Dysphagia Screening Test
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Standardized Swallowing Assessment
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Timed tests of Hinds and Wiles
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Bedside Swallow Assessment
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Toronto Bedside Swallowing Screening Test (TOS-BSST)
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Clinical Examination
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Modified Mann Assessment of Swallowing Ability
Screening tests are considered positive if any of the following are present:
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Dysphonia
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Dysarthria
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Abnormal gag
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Abnormal volitional cough
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Cough after swallowing
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Voice change after swallow
Although bedside screening protocols are commonly used, a systemic review of seven databases including Medline, Embase, and Scopus concluded that no bedside screening protocol provides adequate predictive value for the presence of aspiration.
Other swallowing evaluations
Videofluorographic swallowing study
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This is also known as the Modified Barium Swallow (MBS) and is the “gold standard” for evaluation and treatment of oropharyngeal dysphagia. ,
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It involves providing a patient with a variety of consistencies and textures of liquid and foods mixed with barium.
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As the patient eats or drinks these substances, the provider can observe the anatomy and physiology of the patient’s swallow in real time.
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It can help diagnose an anatomical abnormality (Zenker’s diverticulum, cricopharyngeal bar, stricture, achalasia) that may contribute to the patient’s dysphagia.
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MBS is both diagnostic and therapeutic and allows the provider to have the patient preform compensatory strategies or altered consistencies to see if it helps improve the patient’s swallow.
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Aspiration can be seen easily on the MBS as demonstrated by penetration of contrast material below the true vocal cords ( Fig. 31.3 ).
• Fig. 31.3
Aspiration seen on Modified Barium Swallow (MBS). Thin layer of barium (arrow) on the anterior wall of the trachea.
(From Chhetri DK, Dewan K. Dysphagia Evaluation and Management in Otolaryngology. St. Louis, MO: Elsevier; 2019.)
Fiber optic endoscopic evaluation
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This is used to evaluate the pharyngeal phase of swallowing.
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A fiber optic camera is passed through the nasal passage to the oropharynx for direct visualization.
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This allows for a direct examination of the patient’s anatomy that could be inhibiting the passage of the bolus.
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There is a limitation: no visualization of aspiration because the camera is only viewing passage of the bolus from the oropharynx to the pharynx.
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It can detect secretions in the oropharynx suggestive swallowing dysfunction ( Fig. 31.4 ).
