Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
Dysphagia is the medical term for the symptom of difficulty
swallowing, derived from the Latin and Greek words meaning difficulty eating.
Mechanism of swallowing
Swallowing is a complex action.
Food is first chewed
well in the mouth and mixed with saliva.
The tongue then propels the chewed food
into the throat (pharynx).
The soft palate elevates to prevent the food from
entering the posterior end of the nasal passages, and the upper pharynx
contracts, pushing the food (referred to as a bolus) into the lower pharynx. At
the same time, the voice box (larynx) is pulled upwards by muscles in the neck,
and, as a result, the epiglottis bends downwards. This dual action closes off
the opening to the larynx and windpipe (trachea) and prevents passing food from
entering the larynx and trachea.
The contraction of the muscular pharynx
continues as a progressing, circumferential wave into the lower pharynx pushing
the food along.
A ring of muscle that encircles the upper end of the esophagus,
known as the upper esophageal sphincter, relaxes, allowing the wave of
contraction to push the food from the lower pharynx on into the esophagus. (When
there is no swallow, the muscle of the upper sphincter is continuously
contracted, closing off the esophagus from the pharynx and preventing anything
within the esophagus from regurgitating back up into the pharynx.)
The wave of
contraction, referred to as a peristaltic wave, progresses from the pharynx down
the entire length of the esophagus.
Shortly after the bolus enters the upper
esophagus, a specialized ring of muscle encircling the lower end of the
esophagus where it meets the stomach, known as the lower esophageal sphincter,
relaxes so that when it arrives the bolus can pass on into the stomach. (When
there is no swallow the muscle of the lower sphincter is continuously
contracted, closing off the esophagus from the stomach and preventing contents
of the stomach from regurgitating back up into the esophagus.)
After the bolus
passes, the lower sphincter tightens again to prevent contents of the stomach
from regurgitating back up into the esophagus. It remains tight until the next bolus comes along.
Considering the complexity of swallowing, it is no wonder that swallowing,
beginning with the contraction of the upper pharynx, has been "automated,"
meaning that no thought is required for swallowing once swallowing is initiated.
Swallowing is controlled by automatic reflexes that involve nerves within the
pharynx and esophagus as well as a swallowing center in the brain that is
connected to the pharynx and esophagus by nerves. (A reflex is a mechanism that
is used to control many organs. Reflexes require nerves within an organ such as
the esophagus to sense what is happening in that organ and to send the
information to other nerves in the wall of the organ or outside the organ. The
information is processed in these other nerves, and appropriate responses to
conditions in the organ are determined. Then, still other nerves send messages
from the processing nerves back to the organ to control the function of the
organ, for example, the contraction of the muscles of the organ. In the case of
swallowing, processing of reflexes primarily occurs in nerves within the wall of
the pharynx and esophagus as well as the brain.)
The complexity of swallowing also explains why there are so many causes of
dysphagia. Problems can occur with:
the conscious initiation of swallowing,
propulsion of food into the pharynx,
closing of the nasal passages or larynx,
opening of the upper or lower esophageal sphincters,
physical blockage to the
passage of food, and
transit of the bolus by peristalsis through the body of the
The problems may lie within the pharynx or esophagus, for example,
with the physical narrowing of the pharynx or esophagus. They also may be due to
diseases of the muscles or the nerves that control the muscles of the pharynx
and esophagus or damage to the swallowing center in the brain. Finally, the
pharynx and the upper third of the esophagus contain muscle that is the same as
the muscles that we use voluntarily (such as our arm muscles) called skeletal
muscle. The lower two-thirds of the esophagus is composed of a different type of
muscle known as smooth muscle. Thus, diseases that affect primarily skeletal
muscle or smooth muscle in the body can affect the pharynx and esophagus, adding
additional possibilities to the causes of dysphagia.
Odynophagia and globus sensation
There are two symptoms that are often
thought of as problems with swallowing (dysphagia) that probably are not. These
symptoms are odynophagia and globus sensation.
Odynophagia means painful swallowing. Sometimes it is not easy for
individuals to distinguish between odynophagia and dysphagia. For example, food
that sticks in the esophagus often is painful. Is this dysphagia or odynophagia
or both? Technically it is dysphagia, but individuals may describe it as painful
swallowing (i.e., odynophagia). Moreover, patients with gastroesophageal reflux
disease (GERD) may describe dysphagia when what they really have is odynophagia.
The pain that they feel after swallowing resolves when the inflammation of GERD
is treated and disappears and is presumably due to pain caused by food passing
through the inflamed portion of the esophagus.
Odynophagia also may occur with
other conditions associated with inflammation of the esophagus, for example,
viral and fungal infections. It is important to distinguish between dysphagia
and odynophagia because the causes of each may be quite different.
A globus sensation refers to a sensation that there is a lump in the throat.
The lump may be present continuously or only when swallowing. The causes of a
globus sensation are varied, and frequently no cause is found. Globus sensation
has been attributed variously to abnormal function of the nerves or muscles of
the pharynx and GERD. The globus sensation usually is described clearly by
individuals and infrequently causes confusion with true dysphagia.
The most common swallowing symptom of dysphagia is the sensation that swallowed food is sticking, either in the lower
neck or the chest.
If food sticks in the throat, there may be coughing or
choking with expectoration of the swallowed food.
If food enters the larynx,
more severe coughing and choking will be provoked.
If the soft palate is not
working and doesn't properly seal off the nasal passages, food?particularly
liquids--can regurgitate into the nose with the swallow. Sometimes, food may
come back up into the mouth immediately after being swallowed.
With neurological problems, there may be
difficulty initiating a swallow because food cannot be propelled by the
tongue into the throat.
Elderly individuals with dentures
may not chew their food well and therefore swallow large pieces of solid food
that get stuck.
Polio is caused by a virus and has been around for thousands of years. There
are even Egyptian artifacts portraying individuals with typical features of
post-polio paralysis. Polio has been called