Swallowing Disorders:     Causes    

Overview
The mechanism of swallowing disorders may be either structural or motor. Structural disorders include luminal stenosis and diverticula. Motor disorders include paresis (muscle weakness), sphincteric dysfunction, and spastic disorders. 

Luminal Stenosis
Luminal stenosis occurs as a result of mechanical narrowing of the esophageal lumen in patients with esophageal strictures (Figure 9). Symptoms arise when the swallowed food is too large to pass. The typical symptom in a patient with an esophageal stricture is dysphagia for solid food, often followed by regurgitation of undigested material.

Figure 9. A, Esophageal stricture showing obstruction of food bolus; B, barium swallow.

In general, patients can swallow with little difficulty. This remains true until the swallowing channel is narrowed by about 50%. Even beyond this point, frequency and severity of symptoms may vary substantially, depending on the degree of narrowing, the presence of any associated motor dysfunction, and the choice and preparation of food.

Diverticulum
A diverticulum is a pouch extending out from the normal wall of the swallowing channel. Diverticula (the plural of diverticulum) can develop in either the pharynx or esophagus (Figure 10). Although small diverticula may not cause symptoms, larger diverticula can cause dysphagia for liquids and solids. Regurgitation of undigested food, often hours after ingestion is a characteristic symptom of patients with diverticula.

Figure 10. A, Zenker’s diverticulum; B, esophageal diverticulum.

Motor Disorders 

Paresis
Pharyngeal weakness is commonly associated with neurological conditions, such as a cerebral vascular accident, amyotrophic lateral sclerosis (ALS), head and neck trauma, or brain surgery. Severe esophageal weakness is relatively rare. When it does exist, it is characteristically found in patients with certain types of collagen vascular disorders, especially scleroderma and mixed connective tissue disease. It is also found in patients with certain neurological and muscle conditions that can affect the function of the smooth muscle of the GI tract.

This condition may be asymptomatic. However, when the patient is symptomatic, dysphagia with liquids and solids usually occurs, often associated with regurgitation. Coughing during swallowing is common with pharyngeal weakness, because of aspiration due to pharyngeal retention or impaired laryngeal closure. Mild degrees of weakness are not uncommon in the elderly, in patients with neurological conditions, and in patients with gastroesophageal reflux disease .

Sphincteric Dysfunction
The upper esophageal sphincter (UES) and lower esophageal sphincter (LES) assure unidirectional flow of the swallowed bolus. However, they must relax during swallowing so as not to pose a barrier to flow. The best-described disorder of sphincteric function is achalasia. This is a condition in which the failure of LES relaxation, associated with severe esophageal weakness, combines to retain food in the esophagus. Patients with sphincteric dysfunction typically complain of dysphagia for liquids and solids (Figure 11).

Figure 11. A, Manometric tracings in a normal patient; B, manometric tracing in a patient with achalasia

Spastic Disorders
Whereas spastic disorders of the pharynx are rare, those of the esophagus are common. A certain amount of motor dysfunction may be seen in normal individuals. Esophageal dysmotility may range from mild, infrequent events that are within normal limits, to profound incardination associated with every swallow.

Figure 12. A, Diffuse esophageal spasm; B, barium swallow x-ray.

Diffuse esophageal spasm (Figure 12) represents one extreme of esophageal dysmotility. However, the term is often used loosely to refer to any degree of dysmotility noted by barium or manometric studies (Figure 13).

Figure 13. Manometric studies comparing normal and spastic tracings; A, normal; B, spastic.

Video 5. Click to see a video of neurogenic dysphagia.

Symptoms of neurogenic dysphagia generally include dysphagia and swallow-induced coughing. Nasal regurgitation, if present, strongly suggests a neurogenic process. Some patients fail to recognize the presence or severity of aspiration, possibly because of associated cognitive problems or impaired sensation. Patients may experience recurrent bouts of pneumonia due to swallowed saliva, liquid, and food entering the airway. The prognosis depends on the severity of the swallowing impairment and the treatability of the underlying condition. Among the more treatable causes of neurogenic dysphagia are myasthenia gravis, polymyositis, and both hyper- and hypothyroidism.

Figure 14. Radiographic image of cricopharyngeal dysfunction.

Because the UES protects against esophagopharyngeal regurgitation, an incomplete opening may be a sign of the body’s attempt to prevent regurgitation in the face of downstream obstruction due to esophageal disorders. Alternatively, impairment of the PE opening may reflect inadequate force of bolus propulsion due to pharyngeal weakness in neurogenic dysphagia. Therefore, radiographic evidence of a "tight" PE, may point to pharyngeal or esophageal dysfunction. UES dysfunction must be interpreted with caution. 

Video 6. Click to see a video of a patient with neurogenic pharynx with cricopharyngeal prominence.

 
Isolated UES dysfunction (referred to as cricopharyngeal spasm or cricopharyngeal achalasia) refers to failure of the PE opening without evidence of pharyngeal paresis or evidence of esophageal disease. In patients with this condition, dysphagia is caused by obstruction at the level of the PE, due to either fibrosis (scarring) of the PE or UES dysfunction. Failure of UES relaxation may be documented by manometry.

Figure 15. A, Zenker’s diverticulum; B, barium x-ray study.

 Zenker's (hypopharyngeal) diverticulum is an abnormal, sac-like protrusion on the wall of the lower pharynx (the hypopharynx) (Figure 15). It develops along the posterior pharyngeal wall, just above the upper esophageal sphincter. This area of the pharynx is a region of relative weakness because of the absence of any covering muscle layer. However, this area of weakness is a normal feature of human anatomy and does not in and of itself account for the development of the diverticulum. The primary cause of a Zenker's diverticulum appears to be abnormal relaxation of the upper esophageal sphincter. As a result, the pharyngeal pressure generated during swallowing is increased. Over time, the pharyngeal wall begins to bulge with each swallow until a diverticulum develops and persists between swallows.

Video 7. Click to see a video of Zenker's diverticulum

Pulsion diverticula may be asymptomatic when small. When they grow, however, they retain liquid, food, and regurgitated matter. A patient may wake up coughing, only to find food, recognizable as portions of the meal eaten hours before, in the mouth or on the pillow.

Diverticula may occur in the esophagus as well as the pharynx (Figure 16). Most esophageal diverticula result from abnormal intraluminal pressure as a consequence of increased downstream resistance. This may be due to a stricture, esophageal spasm, or abnormal lower esophageal sphincter function.

Figure 16. A, Esophageal diverticulum; B, barium swallow x-ray; C, endoscopic view

Esophageal rings or webs refer to a short, ring-like band protruding into the lumen. These rings or webs are typically composed of a fold of the lining of the esophagus without any muscle tissue. They may be congenital or acquired, and may occur anywhere in the pharynx or esophagus. The most common is the Schatzki's ring (Figure 17), which by definition occurs at the junction of the esophagus and stomach. Named for the radiologist who described it, Schatzki’s ring is very common and only causes symptoms when it narrows the channel by about 50%. A ring-like band located elsewhere in the pharynx or esophagus is often called a web; the distinction is relatively arbitrary. Webs and rings typically cause intermittent dysphagia for solids, which may remain stable or progress slowly over time.

Figure 17. A, Schatzki’s ring; B, barium swallow x-ray; C, endoscopic

Video 8. Click to view a video of a barium study of a Schatzki's ring.(Quicktime video)

Typically the patient describes intermittent dysphagia of sudden onset, separated by symptom-free periods (without swallowing difficulty). Symptoms are often greatest with tough and
difficult-to-chew foods. Patients may describe particular problems with foods generally considered to be soft, such as pasta or bread. Symptoms are more likely to occur when the patient is eating hurriedly, is offered a limited choice of foods (e.g., when dining out), or is distracted by conversation.

Gastroesophageal reflux disease (GERD) is the most common cause of inflammatory strictures. Inflammation resulting from prolonged contact with irritating gastric contents causes scarring. Thickening of the esophageal wall narrows the channel, producing the dysphagia for solids characteristic of an esophageal stenosis. Esophageal strictures tend to be longer than rings or webs (Figure 18). Unless the cause of inflammation has been removed, the surface of the stricture may appear inflamed and even ulcerated in some cases.

Figure 18. A, B, Normal esophagus compared with erosive esophagitis; A’, B’, endoscopic views

Unlike webs and rings, dysphagia from an inflammatory stricture tends to grow steadily worse over time. The intervals between symptomatic episodes become shorter and the variety of foods that cause symptoms increases over a period that can often be measured in months rather than years. Symptoms may improve when the cause of inflammation is removed (e.g., by effective treatment of reflux disease) and as the swelling associated with inflammation decreases. However, even with effective treatment, symptoms may continue to progress as the scarring increases. With complete eradication of inflammation, scarring gradually stops and the size of the channel stabilizes.

A final cause of esophageal stricture is infiltration of the esophageal wall by a tumor. A tumor may also grow into the channel, further narrowing the lumen. Compared with an inflammatory stricture, malignant strictures tend to progress rapidly, often causing dysphagia for liquids as well as solids within a few months of onset of symptoms (Figure 19). Rapidly progressive dysphagia for solids is a cause of concern and requires early evaluation.

Figure 19. A, esophageal cancer; B, barium swallow x-ray; C, endoscopic view.

Figure 20. A, Barium swallow x-ray showing diffuse esophageal. stricture; B, manometric tracing.

   
Dysphagia typically occurs with both liquids and solids. Chest pain — which may simulate cardiac pain — may be swallow-induced, but may also be unrelated to swallowing. Even when severe, esophageal dysmotility, does not always produce symptoms.

Esophageal spasm is often diagnosed on the basis of clinical symptoms alone. Documentation of abnormal motility may be difficult to obtain because esophageal spasm can be intermittent and therefore may not be detected on short duration studies such as barium x-ray or esophageal manometry. Some degree of abnormal motility occurs in normal asymptomatic volunteers, and the line between esophageal spasm and abnormal contractions that can occur in normal individuals is poorly defined.

Esophageal dysmotility (including spasm) may result from a variety of causes including downstream obstruction, esophageal irritation, or neurological diseases affecting the autonomic nervous system, which controls much of the gastrointestinal function. When no cause has been determined, the condition is referred to as idiopathic esophageal spasm, but this is a relatively rare phenomenon. The most common cause of esophageal spasm is gastroesophageal reflux disease (GERD).

It is important to look for reflux and a stenotic lesion in anyone with symptoms suggestive of esophageal spasm because the treatment of these secondary spastic conditions is different from that of idiopathic spasm. Benign esophageal stenosis is usually treated by esophageal dilation. Reflux is treated with dietary measures designed to avoid stimulation of gastric acid and to decrease the volume of gastroesophageal regurgitation. These measures are usually combined with drugs that decrease acid secretion and improve gastric emptying. Idiopathic spasm, however, may be treated with drugs (smooth muscle relaxants) that decrease the strength of esophageal contractions. Unfortunately, smooth muscle relaxants are often ineffective for the treatment of esophageal spasm.

Video 9. Click to view a video of a barium of diffuse esophageal spasm.(Quicktime movie)

Achalasia
Achalasia is a motor disorder of the esophagus without an obvious etiology. In achalasia, nerve cells (myenteric plexus) located between the esophageal muscle layers are damaged (degenerate). The result is a complete loss of coordinated esophageal contractions (peristalsis) and failure of lower esophageal sphincter (LES) relaxation (Figure 21). This combination produces obstruction at the esophagogastric junction and loss of effective propulsion.

Figure 21. A, Anatomic findings in achalasia; B, endoscopic image; B, radiographic image.

The mean age for the onset of achalasia ranges between 30–60 years, with a peak in the 40s. The prevalence appears to be about 8–12 per 100,000 population. The disorder is more prevalent in men than women with a ratio of about 2:1.

The initial clinical presentation of achalasia is characterized by solid food dysphagia. Patients complain of fullness in the chest while eating, with a filling or overflow sensation as the meal progresses. Food is unable to pass effectively into the stomach and piles up above the LES, resulting in the gradual dilation of the esophagus. This causes dysphagia for liquids and solids and regurgitation of recognizable food, often many hours after ingestion. This form of regurgitation is almost always found in patients with hypopharyngeal or esophageal diverticulum or achalasia. Patients may also complain of substernal chest pain and weight loss.

In most instances, the esophagus becomes dilated, and sometimes tortuous probably as a result of neuropathic changes in the esophagus and the pressure exerted on the esophageal wall by retained food. endoscopic ultrasound (EUS) studies reveal a thickened lower esophageal sphincter (31 mm as compared 22 mm) and thickened muscularis propria.

Video 10. Click to see a video of a barium study of achalasia.(Quicktime movie)

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