Disorders of Swallowing and of the Esophagus
Paralysis of the Swallowing Mechanism. Damage to the 5th, 9th, or
10th cerebral nervecan cause paralysis of significant portions of the
swallowing mechanism. Also, a few diseases, such as poliomyelitis or encephalitis,
can prevent normal swallowing by damaging the swallowing center in the brain
stem. Finally, paralysis of the swal-lowing muscles, as occurs in muscle dystrophy or in failure of
neuromuscular trans-mission in myasthenia
gravis or botulism, can also
prevent normal swallowing.
When the swallowing
mechanism is partially or totally paralyzed, the abnormal-ities that can occur
include (1) complete abrogation of the swallowing act so that swallowing cannot
occur, (2) failure of the glottis to close so that food passes into the lungs
instead of the esophagus, and (3) failure of the soft palate and uvula to close
the posterior nares so that food refluxes into the nose during swallowing.
One of the most serious
instances of paralysis of the swallowing mechanism occurs when patients are
under deep anesthesia. Often, while on the operating table, they vomit large
quantities of materials from the stomach into the pharynx; then, instead of
swallowing the materials again, they simply suck them into the trachea because
the anesthetic has blocked the reflex mechanism of swallowing. As a result,
such patients occasionally choke to death on their own vomitus.
Achalasia and Megaesophagus. Achalasiais a condition in which the lower esophagealsphincter fails to
relax during swallowing. As a result, food swallowed into the esophagus then
fails to pass from the esophagus into the stomach. Pathological studies have
shown damage in the neural network of the myenteric plexus in the lower two
thirds of the esophagus. As a result, the musculature of the lower esoph-agus
remains spastically contracted, and the myenteric plexus has lost its ability
to transmit a signal to cause “receptive relaxation” of the gastroesophageal
sphincter as food approaches this sphincter during swallowing.
When achalasia becomes
severe, the esophagus often cannot empty the swallowed food into the stomach
for many hours, instead of the few seconds that is the normal time. Over months
and years, the esophagus becomes tremendously enlarged until it often can hold
as much as 1 liter of food, which often becomes putridly infected during the
long periods of esophageal stasis. The infection may also cause ulcera-tion of
the esophageal mucosa, sometimes leading to severe substernal pain or even
rupture and death. Considerable benefit can be achieved by stretching the lower
end of the esophagus by means of a balloon inflated on the end of a swallowed
esophageal tube. Antispasmotic drugs (drugs that relax smooth muscle) can also
be helpful.
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