Functional Disorders That Lead to Structural Issues - pediagenosis
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Saturday, May 9, 2020

Functional Disorders That Lead to Structural Issues

Functional Disorders That Lead to Structural Issues
Oropharyngeal dysphagia is an abnormality in the proximal swallowing mechanism affecting bolus propulsion from the oral cavity to the level of the pharyngoesophageal junction, the level of the cricopharyngeal muscle, the upper esophageal sphincter (UES), or the cervical esophagus. Pharyngonasal regurgitation results from the retropulsion of the bolus into the nasal cavity, and laryngeal aspiration is a result of hypopharyngeal stasis and vallecula pooling. Both are a consequence of a functional or structural obstruction, impeding bolus propulsion.

Dysphagia due to neurologic injury results from an injury to the central or peripheral nervous system, regardless of etiology. Bilateral cortical damage such as that following a cerebrovascular accident can result in reduced lingual control and loss of initiation of the swallowing reflex, which results in delayed swallowing and reduced pharyngeal peristalsis. Infarcts affecting the control centers for the nucleus ambiguus cause unilateral paralysis of the pharyngeal and laryngeal musculature, resulting in poor glottic closure complicated by hypopharyngeal stasis and laryngotracheal aspiration. Amyotrophic lateral sclerosis is a progressive neurodegenerative disease causing motor neuron degeneration in the brain, brainstem, and spinal cord. Weakness, muscle atrophy, and fasciculation of the musculature lead to poor bolus handling, resulting in abnormal swallowing. Delayed or incomplete opening of the UES leads to hypopharyngeal stasis, vallecular pooling, and, ultimately, laryngotracheal aspiration. Lesions to the cranial nerves innervating the UES can cause uncoordinated or reduced sphincter opening, leading to a functional obstruction of the UES; this obstruction coupled with a contracting pharynx may cause pharyngooral regurgitation, resulting in pharyngolaryngotracheal aspiration or nasal regurgitation. Neurogenic swallowing abnormalities are visualized by videofluoroscopy. The traditional method uses a single form of liquid barium swallow and is performed by a radiologist. The currently preferable, modified method uses multiple barium-infused consistencies for swallowing and is performed by a speech pathologist. The modified barium study has the oral pharyngeal advantage of being able to capture subtle abnormalities in bolus transfer from the oral cavity to the pharyngoesophageal border. Treatment of disordered swallowing secondary to cortical disturbances begins with education, dietary manipulation, and relearning techniques; alternative nutrition routes, such as a percutaneously placed feeding tube, are reserved for advanced disease. Cricopharyngeal myotomy has been tried with some degree of success in the treatment of cricopharyngeal dysfunction induced by cranial nerve damage. The goal of this procedure is to provide a less obstructed route for the bolus to travel through for entrance into the esophagus (see Plate 2-72).
Dysphagia secondary to a primary muscle disease is best illustrated with a progressive degenerative disease such as muscular dystrophy, particularly the oculopharyngomuscular variant. Bilateral ptosis is a primary manifestation of the disease, with dysphagia appearing prior to or simultaneously with the ptosis. They are both late and progressive manifestations of the disease. Pharyngooral regurgitation is characteristic of dysphagia resulting from a weak pharyngeal musculature incapable of peristaltic contractions of sufficient amplitude to move the bolus through the UES. Tracheobronchial symptoms occur from poor control of laryngeal muscles, pharyngeal muscle weakness, and hypopharyngeal stasis. Videofluoroscopy demonstrates normal initiation of swallowing, impaired barium clearance from the pharynx with concurrent vallecular pooling, and reduced UES opening due to incomplete or delayed relaxation, with many demonstrating a cricopharyngeal bar. Treatment is traditionally supportive and includes dietary manipulation, education, and counseling, plus alternative nutritional feeding when the disorder is severe. Cricopharyngeal myotomy has been used with good results in small patient series. The success of the procedure likely results from enlargement of the pharyngoesophageal opening following the myotomy. Simply stated, a path of least resistance is created by the procedure.
Cricopharyngeal achalasia presents with oropharyngeal dysphagia due to cricopharyngeal dysfunction that may or may not coexist with a pharyngeal diverticulum (Zenker diverticulum). Cricopharyngeal achalasia is characterized by incomplete relaxation of the UES or by a lack of coordination between UES opening and pharyngeal contractions. It can arise from an intrinsic muscle defect or from underlying neurologic dysfunction producing high UES pressures. By definition, there should be strong pharyngeal contractions acting against a poorly relaxing UES, a condition that presents as a functional obstruction. Patients with cricopharyngeal achalasia present with symptoms of dysphagia primarily for solids, pharyngooral regurgitation resulting from the strong pharyngeal contractions acting against a noncompliant UES, and resultant laryngotracheal aspiration. Videofluoroscopy demonstrates barium pooling above a closed UES with or without the presence of a cricopharyngeal bar. A restrictive myopathy secondary to fibrosis or an infiltrative process causing the reduced compliance of the cricopharyngeus muscle has been implicated in the pathogenesis; however, because the response to successive bougie pharyngoesophageal dilations is inconsistent, disease at the level of the muscle is not likely to be the only causative factor in this condition. Manometric findings of a hypertensive UES and a frequent positive response to botulinum toxin suggest an imbalance in excitatory inhibition from acetylcholine receptors and inhibitory neurotransmitters, as seen in classic achalasia. Botulinum toxin has been shown to be an effective temporary therapy reducing cricopharyngeal achalasia in adults and children in much the same way as it has been used in esophageal achalasia. In this condition commercially manufactured botulinum toxin is diluted with preservative-free normal saline, and under endoscopic visualization, an injection of the medication is placed in each of the four quadrants of the UES. Botulinum toxin irreversibly destroys the treated acetylcholine receptor; however, this treatment is temporary, lasting only 6 to 9 months, due to growth of new receptors. The correlation of symptoms with radiologic dysfunction, manometric abnormalities of a hypertensive UES, and poor pharyngeal clearance favors a positive response to botulinum injections and a good response to cricopharyngeal myotomy by either surgical or endoscopic techniques.

Cricopharyngeal bar is a radiographic finding that presents as a prominent and persistent posterior indentation at the level of the lower third of the cricoid cartilage; it is best seen on lateral views. Histologically, degenerative muscle fibers and fibrosis were found on dissected surgical specimens. They are present in both symptomatic and asymptomatic individuals. Esophageal dilation has been successfully used to treat dysphagia in elderly individuals with a cricopharyngeal bar.
Zenker diverticulum is formed in an area of anatomic weakness known as the Killian triangle, which is bordered inferiorly and posteriorly by the superiormost fibers of the cricopharyngeal muscle and superiorly by the inferior fibers of the inferior constrictor muscles of the posterior pharynx. This diverticulum, or outpouching, is created by strong pharyngeal peristaltic contractions against a noncompliant upper esophageal or cricopharyngeal sphincter. This poorly coordinated movement creates high intrabolus pressures within the hypopharynx, leading to the development of a pulsion diverticulum. Symptoms and complications of the diverticulum vary with the size of the lesion. The most common presenting symptoms include dysphagia, regurgitation of undigested food, especially in the supine position, choking, aspiration, and halitosis. A small diverticulum is typically asymptomatic and inci- dentally found on upper endoscopy or during a barium examination. On radiologic evaluation, the pharyngoesophageal diverticulum is seen as a midline protrusion at the level of the posterior hypopharyngeal wall, just above the cricopharyngeal muscle. A large diverticulum can cause considerable anatomic distortion, leading to a functionally obliterated or closed esophageal lumen. Because progressive enlargement is rare, in individuals with a small diverticulum, observation may be the only required intervention; in patients with large symptomatic diverticula, surgical or endoscopic management is required. Because the diverticulum developed as a result of a noncompliant cricopharyngeal muscle, therapeutic intervention involves two steps, diverticulectomy and cricopharyngeal myotomy. Traditionally, treatment was surgical with an open or a transoral endoscopic approach using a rigid or flexible endoscope. Regardless of the mode of entrance, large diverticula can be inverted, suspended (diverticulopexy), or resected. Today the endoscopic approach is favored for diverticula of less than 5 cm. A single lumen is created with ablation of the upper esophageal sphincter by incising the muscular layer of the septum, which is composed of the posterior esophageal wall and anterior wall of the diverticulum and includes the upper esophageal sphincter. Recurrence is rare when a cricopharyngeal myotomy is performed at the same time as the diverticulectomy. Flexible endoscopic techniques have been shown to be as safe as rigid endoscopic treatment for diverticula that are less than 5 cm, and they have the advantage of not requiring general anesthesia. Myotomy can be done using the needle knife technique, argon plasma coagulation, and a monopolar forceps.

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