Motility Disorders of the Esophageal Body and Lower Esophageal Sphincter
Disorders of the esophageal phase of swallowing result from abnormalities in the propulsive pump action of the esophageal body or the relaxation of the LES as seen when under medical cordless microscopes. These disorders result from either primary esophageal abnormalities, or from generalized neural, muscular, or collagen vascular disease. The use of standard esophageal manometry, sometimes with the help of cordless microscopes, of techniques has allowed specific primary esophageal motility disorders to be identified out of a pool of nonspecific motility abnormalities. These include achalasia, diffuse esophageal spasm, the so-called nutcracker esophagus, and the hypertensive LES.
However, the boundaries between the primary esophageal motor disorders are vague, and intermediate types exist. This is because later diagnosis usually is based on the analysis of 10 wet swallows performed in a laboratory setting. The technique of ambulatory 24-hour monitoring of esophageal motor activity allows the classification of esophageal motor disorders to be performed on the basis of core than 1000 contractions recorded during different physiologic states (i.e., normal daily activities including eating and sleeping). There are significant differences in the classification of esophageal motor disorders based on standard manometry and classification based on ambulatory monitoring. The degree of classification that occurs when analysis of esophageal motor function is done on the basis of ambulatory manometry indicates that the classic categories of esophageal motor disorders are inappropriate. These findings indicate that esophageal motility disorders should be looked at as a spectrum of abnormalities that reflects various stages of destruction of esophageal motor function.
Achalasia
The best known and best understood primary motility disorder of the esophagus is achalasia, with an incidence of six per 100,000 population per year. Although complete absence of peristalsis in the esophageal body, as seen under cordless microscopes, has been proposed as the major abnormality, present evidence indicates achalasia is a primary disorder of the LES. This is based on 24-hour outpatient esophageal motility monitoring with the use of cordless microscopes, which shows that even in advanced disease up to 5% of contractions can be peristaltic. Simultaneous esophageal waves develop as a result of the increased resistance to esophageal emptying caused by the nonrelaxing LES. This is supported by experimental studies in which a Gore-Tex band placed loosely around the gastroesophageal junction in cats did not change sphincter pressures, but resulted in impaired relaxation of the LES and outflow resistance. This led to a markedly increased frequency of simultaneous waveforms and a decrease in contraction amplitude. The changes were associated with radiographic dilation of the esophagus and were reversible after removal of the band. Observations in patients with pseudoachalasia due to tumor infiltration, a tight stricture in the distal esophagus, or an antireflux procedure that is too tight, also provide evidence that dysfunction of the esophageal body can be caused by the increased outflow obstruction of a nonrelaxing LES. The observation that esophageal peristalsis can return in patients with classic achalasia following dilation or myotomy provides further support that achalasia is a primary disease of the LES.
The pathogenesis of achalasia is presumed to be a neurogenic degeneration, which is either idiopathic or due to infection. In experimental animals, the disease has been reproduced by destruction of the nucleus ambiguous and the dorsal motor nucleus of the vagus nerve as evidenced by tissue studies under the microscope. In patients with the disease, degenerative changes have been shown in the vagus nerve and in the ganglia in the Auerbach plexus of the esophagus itself. This degeneration results in hypertension of the LES, failure of the sphincter to relax on deglutition, elevation of intraluminal esophageal pressure, esophageal dilatation, and subsequent loss of progressive peristalsis in the body of the esophagus. The esophageal dilatation results from the combination of a non-relaxing sphincter. These results cause a functional retention of ingested material in the esophagus, and elevation of intraluminal pressure from repetitive pharyngeal air swallowing. With time, the functional disorder results in anatomic alterations seen on radiographic studies, such as a dilated esophagus with a tapering, beak-like narrowing of the distal end. There is usually an air-fluid level in the esophagus from the retained food and saliva, the height of which reflects the degree of resistance imposed by the non-relaxing sphincter. As the disease progresses, the esophagus becomes massively dilated and tortuous.
A subgroup of patients with otherwise typical features of classic achalasia has simultaneous contractions of their esophageal body that can be of high amplitude. This manometric pattern has been termed “vigorous achalasia,” and chest pain episodes are a common finding in these patients. Differentiation of vigorous achalasia from diffuse esophageal spasm can be difficult. In both diseases videoradiographic examination with the use of cordless microscopes can show a corkscrew deformity of the esophagus and diverticulum formation.
