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Excerpt from DysphagiaSynonyms, Key Words, and Related Terms: dysphagia, swallowing disorders, deglutition disorders, disordered eating, difficulty eating, disrupted swallowing, aphagia, enteral feeding, gastrostomy, percutaneous endoscopic gastrostomy, PEG, nasoenteric tube, NET, nasogastric tube, NGT, oroesophageal tube feeding, cricopharyngeal myotomy, CPM, aspiration pneumonia Please click here to view the full topic text: DysphagiaDysphagia is a Greek word that means disordered eating. Dysphagia typically refers to difficulty in eating as a result of disruption in the swallowing process. Dysphagia can be a serious threat to one's health because of the risk of aspiration pneumonia, malnutrition, dehydration, weight loss, and airway obstruction. A number of etiologies have been attributed to dysphagia in populations with neurologic and nonneurologic conditions. Disorders leading to dysphagia may affect the oral, pharyngeal, or esophageal phases of swallowing. Thorough history taking and careful physical examination are important in the diagnosis and treatment of dysphagia. The bedside physical should include examination of the neck, mouth, oropharynx, and larynx. A neurologic examination also should be performed. Several clinical bedside swallowing assessments have been suggested, but videofluoroscopic swallowing studies are accepted as the standard for detecting and evaluating swallowing abnormalities.1 This method not only allows estimation of risks of aspiration and respiratory complications but also helps in determining dietary and compensatory strategies. Fiberoptic endoscopic examination of swallowing may be necessary. Disorders of oral and pharyngeal swallowing are usually amenable to rehabilitation, including dietary modification and training in swallowing techniques and maneuvers. Surgery is rarely indicated for patients with swallowing disorders. In patients with severe disorders, bypassing the oral cavity and pharynx in their entirety and providing enteral nutrition may be necessary. Options include percutaneous endoscopic gastrostomy and intermittent oroesophageal catheterization. For excellent patient education resources, visit eMedicine's Cancer and Tumors Center. Also, see eMedicine's patient education article Cancer of the Mouth and Throat. Normal swallowing physiologyCentral pattern generator During swallowing, muscles are activated in an orderly sequence; they are triggered by volitional cortical drive or peripheral sensory input. Once swallowing is initiated, the cascade of the sequential muscle activation does not essentially alter from the perioral muscles downward. Neural networks that are responsible for this automatic swallowing are called central pattern generator. The brainstem, including the nucleus tractus solitarius and the nucleus ambiguus (with the reticular formation linked to cranial motoneuron pools), is thought to be central pattern generator.2 Three phases of swallowing Deglutition is the act of swallowing, which allows a food or liquid bolus to be transported from the mouth to the pharynx and esophagus, through which it enters the stomach. Normal deglutition is a smooth, coordinated process that involves a complex series of voluntary and involuntary neuromuscular contractions and typically is divided into distinct phases: (1) oral, (2) pharyngeal, and (3) esophageal. Each stage facilitates a specific function; if stages are impaired by pathologic condition, specific symptoms may result. Oral phase The oral preparatory phase refers to the processing of the bolus to render it swallowable; the oral propulsive phase refers to the propelling of food from the oral cavity into the oropharynx. The process begins with contractions of the tongue and striated muscles of mastication. The muscles work in a coordinated fashion to mix the food bolus with saliva and then propel the food from the anterior oral cavity into the oropharynx, where the involuntary swallowing reflex is triggered. The cerebellum controls output for the motor nuclei of cranial nerves V (trigeminal), VII (facial), and XII (hypoglossal). With single swallows of liquid, the entire sequence lasts about 1 second. For swallows of solid foods, a delay of 5-10 seconds may elapse while the bolus accumulates in the oropharynx. Pharyngeal phase The pharyngeal phase is of particular importance, because, without intact laryngeal protective mechanisms, aspiration is most likely to occur during this phase. This phase involves a rapid sequence of overlapping events. The soft palate rises, the hyoid bone and larynx move upward and forward, the vocal folds move to the midline, the epiglottis folds backward to protect the airway, and the tongue pushes backward and downward into the pharynx to propel the bolus downward.3 The tongue is assisted by the pharyngeal walls, which move inward with a progressive wave of contraction from top to bottom. The upper esophageal sphincter relaxes during the pharyngeal phase of swallowing and is pulled open by the forward movement of the hyoid bone and larynx. This sphincter closes after passage of the food, and the pharyngeal structures then return to reference position. The pharyngeal phase of swallowing is involuntary and totally reflexive, so no pharyngeal activity occurs until the swallow reflex is triggered. This swallowing reflex lasts approximately 1 second and involves the motor and sensory tracts from cranial nerves IX (glossopharyngeal) and X (vagus). Esophageal phase In the esophageal phase, the bolus is propelled downward by a peristaltic movement. The lower esophageal sphincter relaxes at initiation of the swallow, and this relaxation persists until the food bolus has been propelled into the stomach. Unlike the upper esophageal sphincter, the lower sphincter is not pulled open by extrinsic musculature. Rather, it closes after the bolus enters the stomach, thereby preventing gastroesophageal reflux. The medulla controls this involuntary swallowing reflex, although voluntary swallowing may be initiated by the cerebral cortex. An interval of 8-20 seconds may be required for contractions to drive the bolus into the stomach. PathophysiologyDisorders of swallowing may be categorized according to the swallowing phase affected. A number of dysphagic problems can be identified during each phase of deglutition. Oral phase Oral-phase disorders affecting the oral preparatory and oral propulsive phases usually result from impaired control of the tongue. Patients may have difficulty chewing solid food and initiating swallows. When drinking a liquid, patients may find it difficult to contain the liquid in the oral cavity before swallowing. As a result, liquid spills prematurely into the unprepared pharynx, often resulting in aspiration. Logemann's Manual for the Videofluorographic Study of Swallowing cites the following oral-phase swallowing symptoms and disorders4:
Pharyngeal phase If pharyngeal clearance is severely impaired, a patient may be unable to ingest sufficient amounts of food and drink to sustain life. In people without dysphasia, small amounts of food commonly are retained in the valleculae or pyriform sinus after swallowing. If there is weakness in or a lack of coordination of the pharyngeal muscles or if there is a poor opening of the upper esophageal sphincter, patients may retain excessive amounts of food in the pharynx and experience overflow aspiration after swallowing. Logemann's Manual for the Videofluorographic Study of Swallowing cites the following pharyngeal-phase swallowing symptoms and disorders4:
Esophageal phase Impaired esophageal function can result in retention of food and liquid in the esophagus after swallowing. This retention may result from a mechanical obstruction, a motility disorder, or an impairment of the opening of the lower esophageal sphincter. Logemann's Manual for the Videofluorographic Study of Swallowing cites the following swallowing symptoms and disorders of the esophageal phase4:
Aspiration Aspiration is the passage of food or liquid through the vocal folds. People who aspirate are at increased risk for pneumonia. People without swallowing abnormalities routinely aspirate microscopic amounts of food and liquid. Gross aspiration, however, is abnormal and may lead to respiratory complications. Several factors influence the effects of aspiration: quantity, depth, physical properties of the aspirate, and pulmonary clearance mechanisms. Aspiration of larger quantities of material is riskier than aspiration of minute quantities of food or liquid. Aspirating material into the distal airways is more dangerous than aspiration into the vocal folds. Solid food may cause fatal airway obstruction. Acidic material is dangerous, because the lungs are highly sensitive to the caustic effects of acid. Aspirating material laden with infectious organisms or even normal mouth flora can cause bacterial pneumonitis. Pulmonary clearance mechanisms include ciliary action and coughing. Aspiration normally provokes a strong reflex cough. If sensation is impaired, silent aspiration may occur. The severity of aspiration can be described by estimating the percentage of the total bolus aspirated or by estimating the depth of bolus invasion into the airway. The Eight-Point Penetration-Aspiration Scale is an example of an estimation tool.6 Frequency Dysphagia, which can be classified as neurologic or nonneurologic, has been reported in several types of disorders. Although dysphagia introduces many confounding variables, it also exerts a large influence on the outcome of rehabilitation (eg, length of hospital stay, mortality/morbidity of the patient). Neurologic swallowing disorders are encountered more frequently in rehabilitation medicine than in most other medical specialties. Stroke is the leading cause of neurologic dysphagia. Approximately 51-73% of patients with stroke have dysphagia, which is the most significant risk factor for the development of pneumonia; this can also delay the patient's functional recovery. Pneumonia accounts for about 34% of all stroke-related deaths and represents the third highest cause of death during the first month after a stroke, although not all of these cases of pneumonia are attributable to the aspiration of food. Therefore, early detection and treatment of dysphagia in patients who have sustained a stroke is very critical. Please click here to view the full topic text: Dysphagia |
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