Chapter 038. Dysphagia (Part 1)

Harrisons Internal Medicine Chapter 38. DysphagiaDysphagia: IntroductionDysphagia is defined as a sensation of "sticking" or obstruction of the passage of food through the mouth, pharynx, or esophagus. However, it is often used as an umbrella term to include other symptoms related to swallowing difficulty. Aphagia signifies complete esophageal obstruction, which is usually due to bolus impaction and represents a medical emergency. Difficulty in initiating a swallow occurs in disorders of the voluntary phase of swallowing. However, once initiated, swallowing is completed normally. Odynophagia means painful swallowing. Frequently, odynophagia and dysphagia occur together. Globus pharyngeus is the sensation of...
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Chapter 038. Dysphagia (Part 1) Chapter 038. Dysphagia (Part 1) Harrisons Internal Medicine > Chapter 38. Dysphagia Dysphagia: Introduction Dysphagia is defined as a sensation of sticking or obstruction of thepassage of food through the mouth, pharynx, or esophagus. However, it is oftenused as an umbrella term to include other symptoms related to swallowingdifficulty. Aphagia signifies complete esophageal obstruction, which is usuallydue to bolus impaction and represents a medical emergency. Difficulty in initiatinga swallow occurs in disorders of the voluntary phase of swallowing. However,once initiated, swallowing is completed normally. Odynophagia means painfulswallowing. Frequently, odynophagia and dysphagia occur together. Globuspharyngeus is the sensation of a lump lodged in the throat. However, no difficultyis encountered when swallowing is performed. Misdirection of food, resulting innasal regurgitation and laryngeal and pulmonary aspiration during swallowing, ischaracteristic of oropharyngeal dysphagia. Phagophobia, meaning fear ofswallowing, and refusal to swallow may occur in hysteria, rabies, tetanus, andpharyngeal paralysis due to fear of aspiration. Painful inflammatory lesions thatcause odynophagia may also cause refusal to swallow. Some patients may feel thefood as it goes down the esophagus. This esophageal sensitivity is not associatedwith either food sticking or obstruction. Physiology of Swallowing The process of swallowing begins with a voluntary (oral) phase thatincludes a preparatory phase during which a food bolus suitable for swallowing isprepared and a transfer phase during which the bolus is pushed into the pharynxby contraction of the tongue. The bolus then activates oropharyngeal sensoryreceptors that initiate the deglutition reflex. The deglutition reflex is centrallymediated and involves a complex series of events. It serves both to propel foodthrough the pharynx and the esophagus and to prevent its entry into the airway.When the bolus is propelled backward by the tongue, the larynx moves forwardand the upper esophageal sphincter (UES) opens. As the bolus moves into thepharynx, contraction of the superior pharyngeal constrictor against the contractedsoft palate initiates a peristaltic contraction that proceeds rapidly downward tomove the bolus through the pharynx and the esophagus. The lower esophagealsphincter (LES) opens as the food enters the esophagus and remains open until theperistaltic contraction has swept the bolus into the stomach. Peristaltic contractionin response to a swallow is called primary peristalsis. It involves inhibitionfollowed by sequential contraction of muscles along the entire swallowingpassage. The inhibition that precedes the peristaltic contraction is calleddeglutitive inhibition. Local distention of the esophagus from residual foodactivates secondary peristalsis. Muscles of the oral cavity, pharynx, UES, and cervical esophagus arestriated and are directly innervated by the lower motor neurons carried in thecranial nerves. Oral cavity muscles are innervated by the Vth and the VIIth cranialnerves and the tongue muscles by the XIIth cranial nerve. Pharyngeal muscles areinnervated by the IXth and the Xth cranial nerves. The UES consists of constrictor and dilator muscles. The constrictormuscles include the cricopharyngeus and inferior pharyngeal constrictor muscles.The dilator muscles include a number of suprahyoid muscles including thegeniohyoid muscle. The constrictor muscles are innervated by the Xth cranialnerves and the dilator muscles are innervated by the XIIth and also the Vth and theVIIth cranial nerves. The UES remains closed owing to the elastic properties of itswall and to neurogenic tonic contraction of the cricopharyngeus muscle. Inhibitionof the vagal excitatory activity in the central nervous system relaxes thecricopharyngeus, and contraction of the dilator muscles opens the UES by causingupward and forward displacement of the larynx. The neuromuscular apparatus for peristalsis is different in cervical andthoracic parts of the esophagus. The cervical esophagus, like the pharyngealmuscles, is composed of striated muscles and is innervated by lower motorneurons in the vagus (Xth cranial) nerve. Peristalsis in the cervical esophagus isdue to sequential activation of the vagal motor neurons in the nucleus ambiguus. In contrast, the thoracic esophagus and LES are composed of smooth-muscle fibers and are innervated by excitatory and inhibitory neurons within theesophageal myenteric plexus. Neurotransmitters of the excitatory nerves areacetylcholine and substance P, and of the inhibitory nerves are vasoactiveintestinal peptide (VIP) and nitric oxide. Separate group ...