ABSTRACT
The esophagus is a hollow conduit with sphincters at each end whose main goal is to stay empty in spite of numerous intrusions from above or below. Functionally, the esophagus may be divided into three areas: the upper esophageal sphincter (UES), the esophageal body, and the lower esophageal sphincter (LES). The UES is a striated muscle that is tonically closed due to continuous neural excitation. It opens during swallowing, contracts during inspiration, and protects the airway from gastric content during episodes of gastroesophageal reflux (GER). The esophageal body has striated muscle in the upper third, mixed striated and smooth muscle in the middle third, and only smooth muscle in the lower third. This is important to remember because there are motility disorders that affect only the striated or the smooth muscle, causing dysfunction of the upper or the lower part of the esophagus, respectively. Swallowing initiates the primary peristalsis, a contraction that clears the esophagus from pharyngeal contents. Secondary peristalsis eliminates gastric content during episodes of GER. The LES is a high-pressure area between the esophagus and the stomach; this constitutes the main barrier against GER. The LES relaxes I to 2 sec after swallowing and remains open for 6 to 8 sec. An impaired LES function, characterized either by a low-pressure sphincter or a sphincter with an excessive frequency of relaxations, leads to GER, a condition covered elsewhere in this book (see Chap. 19).
2.1 Disorders of the Upper Esophageal Sphincter The most common disorder of the UES is cricopharyngeal achalasia, involving the failure of the UES to open completely or to open in synchrony with pharyngeal contractions. Symptoms suggestive of cricopharyngeal achalasia include choking, tracheal aspirations with repetitive coughing episodes, nasopharyngeal regurgitation, drooling, and poor eating (I). Often, patients are more symptomatic on swallowing liquids as opposed to solids, a differentiating characteristic from patients with a fixed, lumen-occluding lesion. Dysfunctions of the UES are often accompanied by other evidence of neurological or muscular disease, such as cerebral palsy, familial dysautonomia, Silver-Russell syndrome, 5p-(cri-du-chat) syndrome, muscular dystrophy, and minimal-change myopathy (2). ArnoldChiari malformations have also been associated with dysphagia and UES dysfunction in young children, and brainstem magnetic resonance imaging should be performed in children with cricopharyngeal achalasia to seek such malformation. Surgical decompression of Arnold-Chiari malformation leads to complete clinical and manometric resolution (3). The diagnostic assessment of a child with suspected UES dysfunction begins with a complete examination of mouth, neck, and cranial nerves. Videofluoroscopy and nasopharyngeal endoscopy are the most accurate diagnostic means to assess UES function. A modified barium swallow with different consistency boluses ("cookie swallow") allows a careful assess-
ment of the pharyngeal and esophageal portion of the swallowing process. Cricopharyngeal achalasia is demonstrated radiologically as a horizontal' 'bar" during swallowing, often accompanied by aspiration of radiopaque material (Fig. 2). Esophageal manometry provides information complementary to the radiological study (4). Conservative treatment of DES dysfunction may be indicated in young infants, because spontaneous improvement may occur. Dietary modifications include elimination of foods and liquids that are easily aspirated. Foods with thicker consistency are usually better tolerated because of their adherence to the pharyngeal wall. Drinking of thickened liquids through a straw may also be helpful in controlling the volume of ingested liquids. In older children, resolution of symptoms has been achieved with either bougienage, surgical and laser myotomy, and injection of botulinum toxin (5). Difficulty in swallowing due to decreased pressure of pharyngeal contractions may be one of the presenting symptoms of botulism. Nitrazepam has been associated with delayed cricopharyneal relaxation, causing drooling and aspiration (6).
