Esophageal motor disorders can be classified as either primary or secondary. Primary disorders refer to those that usually affect the esophagus alone and have no known etiology. Secondary disorders are motility derangements caused by some other systemic or local condition. Examples of secondary disorders include acid-reflux-induced dysmotility, dysmotility related to the neuropathy associated with diabetes or alcoholism, and motor dysfunction secondary to esophageal involvement in scleroderma or other connective tissue disorders. The well-defined primary motor disorders include the hypertensive peristaltic or "nutcracker" esophagus, diffuse esophageal spasm and achalasia (Figure 6). Many cases of primary motility disorders are actually "nonspecific," having a variety of abnormalities that do not fulfill criteria established for the well-defined motor disorders of the esophagus.

Patients with primary motor disorders typically present with dysphagia and/or chest pain. The pain is often qualitatively similar to angina pectoris and has been classically attributed to smooth-muscle spasm. However, recent studies have suggested that the pain is secondary to a lowered sensory threshold to esophageal stimuli such as distention or acid. Some patients with motor disorders will have secondary GERD because of poor clearing or poor LES function. Here, heartburn and regurgitation may be prominent symptoms.

The diagnosis of a motor disorder can be made on the basis of history and barium swallow x-ray. If there is dysphagia referred to the retrosternal area and no evidence of a structural lesion on x-ray, then by exclusion the patient's dysphagia is related to a motor disorder. As mentioned previously, the quality of the dysphagia (e.g., sporadic, unpredictable dysphagia to both liquids and solids) is also helpful in differentiating motor disorders from structural causes of dysphagia. During fluoroscopy, the radiologist is usually able to detect abnormalities of motor function as the barium is swallowed. The use of a solid bolus, such as a piece of bread soaked in barium, may be helpful in diagnosing esophageal rings or webs. Endoscopy primarily rules out secondary causes of the disorder (i.e., ulcerative esophagitis and neoplasm). In order to define specifically the type of motor disorder present, however, esophageal motility studies are required. The manometric features of the important esophageal motor disorders are depicted schematically in Figure 6.

This uncommon primary motility disorder is characterized by aperistalsis in the body of the esophagus, an elevated LES pressure and absent or incomplete LES relaxation in response to swallowing. Failure of LES relaxation leads to progressive proximal dilation of the esophagus with consequent elevated resting intraesophageal pressures. On x-ray the esophagus is dilated, and retained food and fluid may be present. The distal esophagus narrows in a beak-like fashion (Figure 7A). This "beak" represents the hypertonic, nonrelaxing LES. In some patients there are associated vigorous nonperistaltic contractions in the esophageal body, a condition called vigorous achalasia. Achalasia is caused by degeneration of inhibitory neurons within the esophageal and LES myenteric plexus. Nerve damage also occurs in the vagal nerve trunks and the dorsal motor nuclei. The parasite Trypanosoma cruzi, which is endemic in Brazil, can cause achalasia by destroying myenteric neurons (Chagas' disease). Neoplastic disease can also interfere with esophageal and LES nerve function and cause "secondary" achalasia. The cause of the degeneration is unknown in most cases, however.

The cardinal symptom of achalasia is dysphagia, although chest pain and even heartburn may be present. The heartburn is not due to gastroesophageal reflux. It may be caused by lactic acid formed by fermentation of stagnant esophageal contents.

Another common symptom of achalasia is regurgitation of esophageal contents.In mild cases treatment can begin with the use of calcium channel blockers or long-acting nitrates, which have been shown to decrease LES pressure. This is rarely successful in the long term, however. The treatment then usually performed is pneumatic balloon dilation of the LES. This consists of passing a balloon across the sphincter and inflating it rapidly so that the sphincter is forcefully dilated. Pneumatic dilation is successful in alleviating the dysphagia and improving esophageal transport in approximately 70-75% of patients. Patients who do not respond to pneumatic dilation should be treated with Heller myotomy. This consists of a longitudinal incision through the muscle of the LES, which in many centers is now done via a laparoscopic or thoracoscopic approach. Following either pneumatic dilation or Heller myotomy, the patient can develop severe GERD, because the pressure barrier preventing reflux has been destroyed. This tends to be worse after Heller myotomy and has led some surgeons to perform a modified antireflux procedure at the time of myotomy. Because of this problem all patients having successful myotomy or pneumatic dilation should be instructed regarding lifelong antireflux therapy. Usually dietary and posture-type treatment are all that is needed, but in some patients drug therapy is required.

Recent studies have found that injection of botulinum toxin into the muscle of the LES can alleviate dysphagia in approximately two-thirds of patients with achalasia. This therapy is limited because the response is not sustained (average duration is approximately one year), but it may be a useful treatment option in elderly patients who would not tolerate the complications of more invasive therapy. Achalasia patients have an increased risk of developing esophageal cancer and need to be thoroughly investigated if new esophageal symptoms develop.

Patients with scleroderma frequently have esophageal involvement. This may occur even in the absence of obvious skin and joint involvement, although in such cases, Raynaud's phenomenon is almost always present. The initial event is damage to small blood vessels, which in turn leads to intramural neuronal dysfunction. With time, actual muscle damage and fibrosis occur. This results in a very hypotensive LES, as well as weak nonpropulsive esophageal contractions. Scleroderma may also involve the stomach and cause delayed gastric emptying. As a result, patients develop gross GERD. They present with heartburn and regurgitation, as well as dysphagia. The dysphagia can be due to poor esophageal propulsion and/or reflux-induced stricture (Figure 7B). These patients need very aggressive treatment for GERD. Because they have very poor peristaltic function, increasing the barrier at the LES with antireflux surgery may markedly worsen the dysphagia.