Achalasia and Diffuse Esophageal Spasm
Achalasia is an uncommon disease occurring in 1:10,000 to 1:100,000 people. It results from neurodegeneration of the myenteric plexuses in the esophageal body and lower esophageal sphincter, leading to esophageal aperistalsis and incomplete opening of the lower esophageal sphincter. Whereas the former results from a lack of excitatory input to stimulate peristalsis, the latter occurs from decreased nitric oxide mediated inhibitory input, leaving the sphincter in a baseline excitatory state with failure to relax in response to deglutition.
The initiating event in the pathophysiology remains unclear, but both genetic predisposition and postviral autoimmune mechanisms have been described. Clinically, it is a slow progressive process often masquerading as reflux and typically with a long delay in diagnosis. Without effective treatment, the process continues with progressive dilation of the esophagus, at times, to massive pro portions with compression of adjacent structures such as the lung and trachea. Classic symptoms of achalasia are dysphagia to liquids and solids, regurgitation, chest pain, and weight loss. Achalasia patients, however, often learn to adjust their lifestyle to the disease and present with more subtle accommodating symptoms such as slow eating and stereotactic movements with eating, such as sitting up straight or walking during a meal. These maneuvers physiologically increase the longitudinal muscle tone. The diagnosis is made by a combination of compatible symptoms, imaging (radiography and/or endoscopy), and esophageal manometry. Imaging demonstrates a range of findings depending on the severity of the disease. In early stages, a nondilated esophagus with a difficult to pass or incompletely opening lower esophageal sphincter may be seen on endoscopy or radiography. As the disease advances, esophageal dilation is more easily appreciated, often with retained saliva and food present despite prolonged fasting. In the most advanced stages, the esophagus may elongate and dilate similar in appearance to the colon in a process described as “sigmoidization.” Without the ability to alter the underlying neural injury, therapy is aimed at pharmacologic or mechanical disruption of the lower esophageal sphincter to at least allow gravity to facilitate passage of the bolus into the stomach. A simple but relatively shortterm treatment is endoscopic injection of botulinum toxin into the lower esophageal sphincter. Pharmacologically, this suppresses cholinergic stimulatory activity and lowers the lower esophageal sphincter pressure. Mechanical therapies include endoscopy dilation with a highpressure pneumatic balloon to rip sphincter muscle fibers or more precise cutting of the sphincter (myotomy) through a surgical approach. Recently, the latter has been performed completely through endoscopy (peroral endoscopic myotomy) by tunneling through the esophageal submucosa and then incising the inner circular layer of the muscularis propria of the lower esophageal sphincter. Longterm results are not available yet for this novel approach. In severely advanced achalasia with sigmoidization, esophagectomy may be needed. Finally, there is an increased risk of esophageal squamous cell cancer in patients with longstanding endstage disease. The pathophysiology of diffuse esophageal spasm is likely similar to that of achalasia. The pathophysiology, however, reflects a more pronounced form of esophageal disinhibition. Specifically, it is manifested by an incompletely relaxing lower esophageal sphincter but also a shorter time interval from the onset of deglutition to lower esophageal sphincter relaxation (decreased distal latency) and hypertensive esophageal contractions. These patients have dysphagia and/or severe episodic chest pain. Radiographically, a “corkscrew” esophagus may be seen. Treatment is similar to that for achalasia, but the response rate of symptoms, particularly chest pain, is not as robust when compared with the response of dysphagia in achalasia. As a result, additional treatment to control the chest pain is often needed. The treatments are aimed at decreasing esophageal muscle pressures (e.g., with anticholinergic or nitric oxide enhancing medications) or reducing esophageal sensation (e.g., with lowdose tricyclic antidepressants). The number of cases of diffuse esophageal spasm that remain stable or progress to more typical forms of achalasia is variable.