The
GALE
ENCYCLOPEDIA
of
M
EDICINE
The
GALE
ENCYCLOPEDIA
of
M
EDICINE
SECOND EDITION
J A C Q U E L I N E L . L O N G E , E D I T O R D E I R D R E S . B L A N C H F I E L D , A S S O C I A T E E D I T O R
V O L U M E
T-Z
ORGANIZATIONS
STAFF
Jacqueline L. Longe,
Project Editor
Deirdre S. Blanchfield,
Associate Editor
Christine B. Jeryan,
Managing Editor
Donna Olendorf,
Senior Editor
Stacey Blachford,
Associate Editor
Kate Kretschmann, Melissa C. McDade, Ryan
Thomason,
Assistant Editors
Mark Springer,
Technical Specialist
Andrea Lopeman,
Programmer/Analyst
Barbara J. Yarrow,
Manager, Imaging and Multimedia
Content
Robyn V. Young,
Project Manager, Imaging and
Multimedia Content
Dean Dauphinais,
Senior Editor, Imaging and
Multimedia Content
Kelly A. Quin,
Editor, Imaging and Multimedia Content
Leitha Etheridge-Sims, Mary K. Grimes, Dave Oblender,
Image Catalogers
Pamela A. Reed,
Imaging Coordinator
Randy Bassett,
Imaging Supervisor
Robert Duncan,
Senior Imaging Specialist
Dan Newell,
Imaging Specialist
Christine O’Bryan,
Graphic Specialist
Maria Franklin,
Permissions Manager
Margaret A. Chamberlain,
Permissions Specialist
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Mike Logusz,
Graphic Artist
Mary Beth Trimper,
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Electronic Prepress
Evi Seoud,
Assistant Manager, Composition Purchasing
and Electronic Prepress
Dorothy Maki,
Manufacturing Manager
Wendy Blurton,
Senior Manufacturing Specialist
The
GALE
ENCYCLOPEDIA
of
MEDICINE
SECOND EDITION
Since this page cannot legibly accommodate all copyright notices, the acknowledgments constitute an extension of the copyright notice.
While every effort has been made to ensure the reliability of the infor-mation presented in this publication, the Gale Group neither guarantees the accuracy of the data contained herein nor assumes any responsibili-ty for errors, omissions or discrepancies. The Gale Group accepts no payment for listing, and inclusion in the publication of any organiza-tion, agency, instituorganiza-tion, publicaorganiza-tion, service, or individual does not imply endorsement of the editor or publisher. Errors brought to the attention of the publisher and verified to the satisfaction of the publish-er will be corrected in future editions.
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This publication is a creative work fully protected by all applicable copyright laws, as well as by misappropriation, trade secret, unfair com-petition, and other applicable laws. The authors and editor of this work have added value to the underlying factual material herein through one or more of the following: unique and original selection, coordination, expression, arrangement, and classification of the information.
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All rights reserved including the right of reproduction in whole or in part in any form.
ISBN 0-7876-5489-2 (set) 0-7876-5490-6 (Vol. 1) 0-7876-5491-4 (Vol. 2) 0-7876-5492-2 (Vol. 3) 0-7876-5493-0 (Vol. 4) 0-7876-5494-9 (Vol. 5)
Printed in the United States of America 10 9 8 7 6 5 4 3 2 1
Library of Congress Cataloging-in-Publication Data Gale encyclopedia of medicine / Jacqueline L. Longe, editor; Deirdre S. Blanchfield, associate editor — 2nd ed.
p. cm.
Includes bibliographical references and index. Contents: Vol. 1. A-B — v. 2. C-F — v. 3. G-M — v. 4. N-S — v. 5. T-Z.
ISBN 0-7876-5489-2 (set: hardcover) — ISBN 0-7876-5490-6 (vol. 1) — ISBN 0-7876-5491-4 (vol. 2) — ISBN 0-7876-5492-2 (vol. 3) — ISBN 0-7876-5493-0 (vol. 4) — ISBN 0-7876-5494-9 (vol. 5)
1. Internal medicine—Encyclopedias. I. Longe, Jacqueline L. II. Blanchfield, Deirdre S. III. Gale Research Company. RC41.G35 2001
616’.003—dc21
Introduction
. . . .ix
Advisory Board
. . . .xi
Contributors
. . . .xiii
Entries
Volume 1: A-B
. . . .1
Volume 2: C-F
. . . .625
Volume 3: G-M
. . . .1375
Volume 4: N-S
. . . .2307
Volume 5: T-Z
. . . .3237
Organizations
. . . .3603
General Index
. . . .3625
The Gale Encyclopedia of Medicine 2
is a medical
ref-erence product designed to inform and educate readers
about a wide variety of disorders, conditions, treatments,
and diagnostic tests. The Gale Group believes the product
to be comprehensive, but not necessarily definitive. It is
intended to supplement, not replace, consultation with a
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Group has made substantial efforts to provide information
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of the information contained in this product. Readers
should be aware that the universe of medical knowledge
is constantly growing and changing, and that differences
of medical opinion exist among authorities. Readers are
also advised to seek professional diagnosis and treatment
for any medical condition, and to discuss information
obtained from this book with their health care provider.
The Gale Encyclopedia of Medicine 2 (GEM2)
is a
one-stop source for medical information on nearly 1,700
common medical disorders, conditions, tests, and
treat-ments, including high-profile diseases such as AIDS,
Alzheimer’s disease, cancer, and heart attack. This
ency-clopedia avoids medical jargon and uses language that
laypersons can understand, while still providing
thor-ough coverage of each topic. The Gale Encyclopedia of
Medicine 2
fills a gap between basic consumer health
resources, such as single-volume family medical guides,
and highly technical professional materials.
SCOPE
Almost 1,700 full-length articles are included in the
Gale Encyclopedia of Medicine 2, including disorders/
conditions, tests/procedures, and treatments/therapies.
Many common drugs are also covered, with generic drug
names appearing first and brand names following in
parentheses, eg. acetaminophen (Tylenol). Throughout
the Gale Encyclopedia of Medicine 2, many prominent
individuals are highlighted as sidebar biographies that
accompany the main topical essays. Articles follow a
standardized format that provides information at a
glance. Rubrics include:
Disorders/Conditions
Tests/Treatments
Definition
Definition
Description
Purpose
Causes and symptoms
Precautions
Diagnosis
Description
Treatment
Preparation
Alternative treatment
Aftercare
Prognosis
Risks
Prevention
Normal/Abnormal results
Resources
Resources
Key terms
Key terms
In recent years there has been a resurgence of interest
in holistic medicine that emphasizes the connection
between mind and body. Aimed at achieving and
main-taining good health rather than just eliminating disease,
this approach has come to be known as alternative
medi-cine. The Gale Encyclopedia of Medicine 2
includes a
number of essays on alternative therapies, ranging from
traditional Chinese medicine to homeopathy and from
meditation to aromatherapy. In addition to full essays on
alternative therapies, the encyclopedia features specific
Alternative treatment
sections for diseases and
condi-tions that may be helped by complementary therapies.
INCLUSION CRITERIA
A preliminary list of diseases, disorders, tests and
treat-ments was compiled from a wide variety of sources,
including professional medical guides and textbooks as
well as consumer guides and encyclopedias. The general
advisory board, made up of public librarians, medical
librarians and consumer health experts, evaluated the
top-ics and made suggestions for inclusion. The list was sorted
by category and sent to GEM2
medical advisors, certified
physicians with various medical specialities, for review.
Final selection of topics to include was made by the
med-ical advisors in conjunction with the Gale Group editor.
ABOUT THE CONTRIBUTORS
The essays were compiled by experienced medical
writers, including physicians, pharmacists, nurses, and
other health care professionals. GEM2
medical advisors
reviewed the completed essays to insure that they are
appropriate, up-to-date, and medically accurate.
HOW TO USE THIS BOOK
The
Gale Encyclopedia of Medicine 2
has been
designed with ready reference in mind.
• Straight
alphabetical arrangement
allows users to
locate information quickly.
• Bold-faced terms function as
print hyperlinks
that
point the reader to related entries in the encyclopedia.
•
Cross-references
placed throughout the encyclopedia
direct readers to where information on subjects
with-out entries can be found. Synonyms are also
cross-ref-erenced.
• A list of
key terms
are provided where appropriate to
define unfamiliar terms or concepts.
• Valuable
contact information
for organizations and
support groups is included with each entry. The
appendix contains an extensive list of organizations
arranged in alphabetical order.
•
Resources section
directs users to additional sources
of medical information on a topic.
• A comprehensive
general index
allows users to easily
target detailed aspects of any topic, including Latin
names.
GRAPHICS
The
Gale Encyclopedia of Medicine 2
is enhanced
with over 675 color images, including photos, charts,
tables, and customized line drawings.
Intr
MEDICAL ADVISORS
A. Richard Adrouny, M.D.,
F.A.C.P.
Clinical Assistant Professor of
Medicine
Division of Oncology
Stanford University
Director of Medical Oncology
Community Hospital of Los
Gatos-Saratoga
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Laurie Barclay, M.D.
Neurological Consulting Services
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Kenneth J. Berniker, M.D.
Attending Physician
Emergency Department
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Rosalyn Carson-DeWitt, M.D.
Durham, NC
Robin Dipasquale, N.D.
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Faye Fishman, D.O.
Randolph, NJ
J. Gary Grant, M.D.
Pacific Grove, CA
Laith F. Gulli, M.D.
M.Sc., M.Sc.(MedSci), MSA,
Msc.Psych., MRSNZ
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Consultant Psychotherapist in
Private Practice
Lathrup Village, MI
L. Anne Hirschel, D.D.S.
Southfield, MI
Larry I. Lutwick M.D., F.A.C.P.
Director, Infectious Diseases
VA Medical Center
Brooklyn, NY
Ira Michelson, M.D., M.B.A.,
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Physician and Clinical Instructor
University of Michigan
Ann Arbor, MI
Susan Mockus, M.D.
Scientific Consultant
Seattle, WA
Ralph M. Myerson, M.D.,
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Clinical Professor of Medicine
Medical College of Pennsylvania–
Hahnemann University
Philadelphia, PA
Ronald Pies, M.D.
Clinical Professor of Psychiatry
Tufts University
School of Medicine
Boston, MA
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Harvard Medical School
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Lee A. Shratter, M.D.
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The Permanente Medical Group
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LIBRARIAN ADVISORS
Maureen O. Carleton, MLIS
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King County Library System
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Free Library of Philadelphia, PA
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Case Western Reserve University
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VA Medical Center
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Suzanne M. Lutwick
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Brooklyn, NY
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Medical Student
Wayne State University
Detroit, MI
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Demarest, NJ
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Whittingham Cancer Center
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Taeniasis
see
Tapeworm diseases
Tagged red blood cell scan
see
GI bleeding
studies
T’ai chi
Definition
T’ai chi is a Chinese
exercise
system that uses slow,
smooth body movements to achieve a state of relaxation
of both body and mind.
Purpose
As a system of physical exercise used to improve
and maintain health, t’ai chi can be helpful in achieving a
state of physical and mental relaxation while also
strengthening the cardiovascular system.
Precautions
As a very slow and gentle form of moving, t’ai chi
has virtually no side effects. However, if a person has any
doubts about the condition of his or her joints, vertebrae,
or heart, a physician should be consulted.
Description
Developed originally in China as a self-defense
strategy, or martial art, t’ai chi—the “supreme ultimate
fist”—is practiced in modern times primarily as a gentle
exercise technique. Described as “meditation in motion,”
t’ai chi consists of a standing person performing a series
of postures or bodily movements in a slow and graceful
manner, with each movement flowing without pause to
the next. According to Chinese legend, the technique was
created by a Taoist monk who was inspired as he
watched a crane and a snake do battle. Impressed by the
snake’s ability to subtly and swiftly avoid the bird’s
thrusts, he devised a series of self-defense techniques
that do not involve meeting the opponent’s force with
force, but rather stress evading the blow; causing the
opponent’s own momentum to work against him.
T’ai chi is an ancient form of exercise, about 2,000
years old, that at one point had over 100 separate
move-ments or postures. In current practice, there are two popular
versions, of 18 and 37 movements respectively. The fact that
in China 10 million people practice some type of t’ai chi
daily suggests that it is one of the most popular forms of
exercise in the world. In the United States, t’ai chi is learned
in classes in which students (or “players,” as they are called
in China) wear loose, comfortable clothing and either go
barefoot or wear only socks or soft shoes on the feet. In
China, t’ai chi is almost always practiced outdoors at dawn,
and ideally near trees. Unlike other martial arts, t’ai chi is
not competitive. Classes usually begin with a few minutes
of standing
meditation
to calm the mind and gather energy.
Following warm-up exercises, students are taught the basics
of a particular form or posture. Learning forms is not easy,
and it takes some time to master what looks like a simple
position. Properly done postures are done in a relaxed,
art-ful, and linked way, with the circular and rhythmic
move-ments of one position flowing seamlessly into the next.
While strict attention to body position is critical,
proper breathing is considered to be equally important.
Just as movements are slow and continuous and without
strain, breathing should be effortless yet deep. Finally,
both mental and physical balance is considered essential
to t’ai chi. The experienced practitioner of t’ai chi
main-tains perfect body balance throughout the exercise series.
Altogether, the five essential qualities of t’ai chi are:
• Slowness. To develop awareness.
• Lightness. To make movements flow.
• Balance. To prevent body strain.
• Calmness. To maintain continuity.
• Clarity. To focus the mind.
coordination. Many older people find that it boosts their
energy, stamina, and agility, sharpens their reflexes, and
gives an overall sense of well-being. The calming and
meditative aspects of t’ai chi allow many to experience its
ability to relieve
stress
. Some claim t’ai chi to be a healing
therapy, and it is often used to support other treatments for
chronic conditions; arthritis and digestive disorders are
just two examples. Like
yoga
, t’ai chi has several different
styles to suit the individual. Also, it can eventually be done
daily by oneself, and ultimately becomes a very personal
endeavor. Most Westerners find it best to practice t’ai chi
in the same place and at the same time of day, and those
who enjoy it most are those who are not seeking major,
dramatic breakthroughs, but rather who can take pleasure
in small gains that accumulate over a long period of time.
Risks
T’ai chi is a safe exercise system for people of all ages
and fitness levels. Done properly, without any
over-stretch-ing, t’ai chi should not leave a person feeling tired or sore.
Normal results
Besides its overall fitness benefits and
stress
reduc-tion
aspects, regular t’ai chi sessions are said to be
espe-cially helpful for seniors, as they lower their blood
pres-sure. T’ai chi claims to benefit arthritis sufferers, those
recovering from an injury or rehabilitating their hearts, and
also improves balance, and therefore, reduces the risk of
K E Y T E R M S
Arthritis
—Inflammation of the joints.
Cardiovascular
—Relating to the heart and blood
vessels.
Continuity
—Uninterrupted and successive.
Meditation
—An exercise of contemplation that
induces a temporary feeling of relaxation.
Stamina
—Staying power, endurance.
Yoga
—A system of exercise aimed at promoting
the control of the body and the mind.
falling, especially important for the elderly. T’ai chi can
result in a significant improvement in the quality of life for
anyone. But, because of the low stress level of the
exercis-es it is a particularly attractive form of exercise to seniors.
Resources
BOOKS
Crompton, Paul. T’ai Chi.New York: Macmillan, 1996. Guiness, Alma E. Family Guide to Natural Medicine.
Pleas-antville, NY: The Reader’s Digest Association, Inc., 1993. Parry, Robert. T’ai Chi.Chicago: NTC Publishing Group, 1997.
PERIODICALS
Brody, Jane. “T’ai Chi Offers Gentle, Stylized Exercises.”The New York Times, 16 July 1997, C1.
Krucoff, Carol. “Western Science Studies Healing Effects of Ancient Eastern Practice.”The Washington Post, 14 Apr. 1998, 28, 30.
ORGANIZATIONS
The Northeastern T’ai Chi Chuan Association. 163 West 23rd St., 5th Floor., New York, NY 10011 (212) 741-1922.
Leonard C. Bruno, PhD
Tailbone injuries
see
Coccyx injuries
Talipes
see
Clubfoot
Tamoxifen
see
Anticancer drugs
Tamponade
see
Cardiac tamponade
Tapeworm diseases
Definition
Tapeworms are a group of parasitic worms that live
in the intestinal tracts of some animals. Several different
Tape
w
orm diseases
species of tapeworms can infect humans. Tapeworm
dis-ease or cestodiasis occurs most commonly after eating
raw or undercooked meat or fish that contains the
imma-ture form of the tapeworm.
Description
Tapeworm infections pose a serious public health
problem in many less developed countries due to poor
san-itation conditions. The disease is most common where
livestock, such as cattle and pigs, are raised in areas where
human feces are not disposed of in a sanitary manner.
Another common source of human tapeworms are certain
species of freshwater fish. Tapeworm infections tend to
occur more frequently in areas of the world where the
peo-ple regularly eat raw or undercooked beef, pork, or fish.
Persons of all ages and both sexes are susceptible to
tape-worm infection, but children are generally not exposed
until they are old enough to begin eating meat or fish.
Tapeworm is less common in industrialized regions
of the world, but travel to areas in which tapeworm
infec-tions are more common and immigration of people from
these areas serve as new sources of the parasite. Infected
persons are often unaware of the presence of adult
tape-worms in their intestinal tract, as they may have no
obvi-ous symptoms of infection. Some tapeworms can live in
an infected person for over 10 years if diagnosis is not
made and treatment is not administered.
In addition to the typical infection caused by eating
undercooked meat or fish, people may also be directly
infected by ingesting tapeworm eggs shed by the adult
worm. This type of tapeworm infection can lead to a
con-dition referred to as cysticercosis, in which the larvae
continue to develop within tissues other than the
intesti-nal tract. One of the most serious forms of this disease
occurs when the tapeworm larvae infect the central
ner-vous system, a disease referred to as neurocysticercosis.
In contrast to a typical tapeworm infection, which may
not be associated with symptoms, neurocysticercosis is a
serious condition that may cause seizures and is
poten-tially life-threatening.
Causes and symptoms
Several species of tapeworm can infect people. The
two most common species are the pork tapeworm (Taenia
solium) and the beef tapeworm (Taenia saginata).
Improperly treated human sewage may be used to fertilize
pastures or crops. Pigs or cattle become infected by
graz-ing in contaminated pastures or drinkgraz-ing water
contami-nated with tapeworm eggs from human feces. The
pea-sized larvae of these tapeworms are deposited in certain
tissues of the body of infected pigs and cattle, including
the muscles. The infection is then transmitted to people
when raw or undercooked meat containing tapeworm
lar-vae is consumed. The immature tapeworm develops into
the adult form in the human intestine and may remain
there for many years if not identified and treated.
The Taenia
tapeworms attach to the intestinal walls
but cause only mild inflammation at the site of
attach-ment. As a result, most tapeworm carriers show no
symp-toms (asymptomatic) and usually become aware of the
infection only after noticing tapeworm segments in their
feces. Segments of the beef tapeworm may
spontaneous-ly pass through the anus causing a noticeable sensation.
Mild gastrointestinal symptoms, such as nausea or
abdominal
pain
, can occur in infected individuals. In
rare cases where the tapeworm segments migrate into the
appendix, pancreas, or bile duct, there may be a sudden
onset of severe abdominal discomfort.
Cysticercosis is a potentially serious complication of
Taenia solium
infection in which the larvae develop
out-side the intestinal tract. This type of infection is less
common and occurs following accidental consumption
of tapeworm eggs released from the adult worm. These
eggs initially are localized in the anal area, but they may
also contaminate the fingers or other parts of the body.
Infection can occur in the person harboring the adult
tapeworm or in other people with whom that individual
comes in contact. The tapeworm larvae may develop in
various tissues throughout the body. The most serious
clinical problems occur when the larvae develop in the
central nervous system (neurocysticercosis), potentially
Tape
w
orm diseases
causing seizures and other neurological problems. An
important aspect of this type of infection is that poor
hygiene on the part of the individuals harboring an adult
tapeworm can lead to an infection in an individual who
may never consume meat. This is a particular problem if
infected individuals are employed as food handlers.
Another important tapeworm that may infect people
is the fish tapeworm (Diphyllobothrium latum). This is a
frequent human intestinal parasite in many areas where
raw freshwater fish is consumed. Human infection with
the fish tapeworm is referred to as diphyllobothriasis.
Feces from infected hosts or raw sewage contaminates a
fresh water source. Tapeworm larvae are initially
ingest-ed by freshwater crustaceans and then are eaten by fish.
Human infection occurs when a person consumes raw
fish contaminated with the tapeworm larvae. Adult
tape-worms then develop in the human intestinal tract.
Most infections with the fish tapeworm are not
associ-ated with symptoms. The tapeworm causes little damage to
the lining of the intestine. Infected individuals may report
diarrhea
,
fatigue
, weakness, or sensations of hunger more
commonly than uninfected individuals. One problem
unique to this tapeworm is that it may compete with the
host for absorption of vitamin B
12from the small intestine,
causing the person to become deficient in this vitamin and
leading to a condition called
pernicious anemia
.
Two smaller species of tapeworms may also infect
people. The dwarf tapeworm (Hymenolepis nana) is a
common infection throughout the world that can be
passed from one person to another. Transmission is
usual-ly the result of inadvertent ingestion of tapeworm eggs
from feces eliminated by infected individuals. As a result,
infection with this tapeworm is encountered most
fre-quently in children, the developmentally disabled, and
psychiatric patient populations. Abdominal pain that is
not localized to any particular area is the most common
complaint. Patients may experience loose bowel
move-ments or diarrhea with mucus, but bloody diarrhea is rare.
Another small tapeworm capable of infecting people
is the rodent tapeworm (Hymenolepis diminuta). Rats,
mice, and other rodents are the usual hosts for the adult
tapeworm (definitive host), but humans can become
infected following accidental consumption of insects
containing tapeworm larvae. Meal worms or grain
bee-tles that infest cereal, flour, or dried fruit are the most
likely source of infection. Most human infections are not
associated with symptoms, although some individuals
report headaches, anorexia, nausea, and diarrhea.
Diagnosis
Identification of tapeworm segments or eggs in a stool
sample is necessary for diagnosis of an adult tapeworm
infection. In many cases, a tentative diagnosis may be
made on the basis of a patient’s description of short chains
of tapeworm segments in their stool. Further evaluation is
recommended to determine the actual species involved
since infection with Taenia solium is potentially more
seri-ous due to the added risk of cysticercosis. Whenever
possi-ble, tapeworm segments should be carefully collected in
water or salt solutions, using strict precautions to avoid
contamination. Stool examination should be performed in
a laboratory having experience in the diagnosis of
intesti-nal parasites. It is recommended that at least three stool
samples be collected on alternate days to increase the
like-lihood of being able to make an accurate diagnosis.
Although the general appearance of tapeworm
seg-ments from the two Taenia
species is quite similar, trained
laboratory personnel can detect distinct differences
between the beef and pork tapeworms when samples are
examined under a microscope. Tapeworm segments and
eggs from the fish tapeworm and the dwarf tapeworm
have characteristic appearances that allow accurate
differ-entiation from the Taenia
species of worms. Other
diag-nostic procedures may be necessary when cysticercosis is
suspected. Blood samples from an infected individual are
collected to look for the presence of antibodies against the
tapeworm larvae. In cases in which infection of the
cen-tral nervous system is present, advanced imaging tests,
such as
computed tomography scans
and
magnetic
res-onance imaging
(MRI), may be necessary to determine
the exact location of the tapeworm larvae within the body.
Tape
w
orm diseases
Treatment
Effective treatment of tapeworm infections involves
administering compounds that are toxic to the adult
worm. Many of the early treatments were also somewhat
toxic to the patient, so treatment was often quite an
ordeal. Newer medications are much more easily
tolerat-ed and are highly effective in eliminating the parasite
from the body.
One treatment that has been in use since the early
1960s is niclosamide (Niclocide). This drug is poorly
absorbed from the digestive tract and rapidly kills
tape-worms upon exposure. It has been shown to be effective
against Taenia
species and the fish tapeworm, but
treat-ment of the dwarf tapeworm (Hymenolepis nana) may
require a more prolonged treatment schedule. Side
effects reported with niclosamide are infrequent and
typ-ically mild. When present, side effects may include
nau-sea, abdominal discomfort, vomiting, diarrhea,
light-K E Y T E R M S
Cestodiasis
—Parasitic infection caused by the
presence of adult tapeworms of the class Cestoda
within the intestinal tract. Infection is caused by
accidental consumption of tapeworm larvae.
Cysticercosis
—Parasitic infection caused by the
presence of immature tapeworm larvae (cysticerci)
that have developed outside the intestinal tract.
Infection is caused by accidental consumption of
tapeworm eggs.
Diphyllobothriasis
—Parasitic infection caused by
the presence of tapeworms from the
Diphylloboth-rium
genus, such as the fish tapeworm (
Diphyl-lobothrium latum
).
Hymenolepiasis
—Parasitic infection caused by the
presence of tapeworms from the
Hymenolepis
genus, such as the dwarf tapeworm (
Hymenolepis
nana
) or the rodent tapeworm (
Hymenolepis
diminuta
).
Neurocysticercosis
—Parasitic infection caused by
the presence of immature tapeworm larvae within
the central nervous system.
Pernicious anemia
—Type of anemia caused by a
deficiency in vitamin B
12.
Taeniasis
—Parasitic infection caused by the
pres-ence of tapeworms from the
Taenia
genus, such as
the pork tapeworm (
Taenia solium
) or the beef
tapeworm (
Taenia saginata
).
headedness, and skin rash. This medication should be
taken in the morning on an empty stomach. The tablets
are chewed thoroughly and swallowed with water. For
young children, the tablets may be pulverized and mixed
with water. Patients are allowed to eat two hours after
treatment. Recommended dosage is 2 grams for adults
and about half this for children.
Another oral medication that has been shown to be
95% effective in the treatment of tapeworm infections
associated with both Taenia and Diphyllobothrium latum
species is praziquantel (Biltricide). Side effects reported
for praziquantel are mild and appear to be short-lived.
They include nausea, abdominal pain,
itching
, sore
joints, and muscle pain.
It is recommended that follow-up stool samples be
examined at one month and three months after treatment
has been completed. Treatment can be considered
success-ful if no eggs are present in several stool samples. It should
be noted that the tapeworm medications do not kill the
tape-worm eggs when they kill the adult tape-worm, so the potential
for infection with eggs still exists as the dead worm
seg-ments are passed. Proper personal hygiene in individuals
receiving treatment will greatly reduce this potential.
Cases of neurocysticercosis, where larvae have
devel-oped in the central nervous system, may also be treated
with praziquantel or albendazole. If the patient is treated
promptly, damage to the central nervous system will be
minimized.
Prognosis
When confined to the intestinal tract, tapeworms
cause minimal damage to their human host. Once the
diagnosis of an intestinal tapeworm infection has been
made, prognosis following treatment with niclosamide or
praziquantel is good. The worms can be eliminated from
the intestines with oral treatment, and there are usually
no residual side effects. Serious problems from
tape-worm infections occur when tapetape-worm eggs are
con-sumed and the larvae localize in tissues outside the
digestive tract (cysticercosis). Prompt diagnosis and
treatment of this condition is necessary to prevent
perma-nent damage to the central nervous system and other
internal organs. Untreated cases of cysticercosis have the
rare potential to be life-threatening.
Prevention
The best way to prevent infection with tapeworms
is to eliminate the exposure of livestock to the
tape-worm eggs by properly disposing of human feces. The
next best strategy is to thoroughly cook or freeze all
meat and fish before it is eaten to prevent consumption
Tape
w
of live tapeworm larvae in infected samples. Larval
cysts in pork and beef are killed by moderate
tempera-tures of 150°F (65°C) or if frozen for at least 12 hours.
Proper cooking of freshwater fish could also eliminate
the possibility of human infection with the fish
tape-worm. Freezing fresh fish for 24 hours will also kill the
larval form.
Resources
PERIODICALS
Despommier, Dickson D. “Tapeworm Infection: The Long and the Short of It.”New England Journal of Medicine327 (3 Sept. 1992): 727-728.
Pearson, Richard D., and Erik L. Hewlett. “Niclosamide Thera-py for Tapeworm Infections.”Annals of Internal Medicine
102 (Apr. 1985): 550-551.
Schantz, Peter M. “Tapeworms (Cestodiasis).”
Gastroenterolo-gy Clinics of North America25 (Sept. 1996): 637-653.
Schantz, Peter M., et al. “Neurocysticercosis in an Orthodox Jewish Community in New York City.”New England
Journal of Medicine327 (3 Sept. 1992): 692-695.
Tanowitz, Herbert B., Louis M. Weiss and Murray Wittner. “Diagnosis and Treatment of Intestinal Helminths: Com-mon Intestinal Cestodes.”The Gastroenterologist1 (Dec. 1993): 265-273.
Geoffrey N. Clark, DVM
Tardive dyskinesia
Definition
Tardive dyskinesia is a mostly irreversible
neurolog-ical disorder of involuntary movements caused by
long-term use of antipsychotic or neuroleptic drugs.
Description
Antipsychotic or neuroleptic drugs are powerful
tranquilizers generally prescribed for serious psychiatric
disorders, as well as neurological and gastrointestinal
disorders. Some common antipsychotics are:
chlorpro-mazine HCl (Thorazine), thioridazine HCl (Mellaril),
haloperidol (Haldol), perphenazine (Trilafon),
thiothix-ene (Navane), trifluoperazine HCl (Stelazine), and
fluphenazine HCl (Permitil, Prolixin).
When these drugs are used long term, tardive
dyski-nesia (TD) can result. About 20 percent of people taking
antipsychotic drugs
for more then one year become
affected by TD. The prevalence of TD tends to be highest
among elderly patients and among women.
Causes and symptoms
TD usually appears after years of antipsychotic drug
use, and seems to be related to the total lifetime dose of
medication. The symptoms include the following:
• tongue protrusion
• grimacing
• rapid eye blinking
• lip smacking, pursing, or puckering
• rapid movement of the arms or legs
• other involuntary movements of the head, face, neck
and tongue muscles
Diagnosis
The diagnosis of TD is suspected upon observation
of involuntary movements of the head, neck, face, and
tongue in individuals who have a history of antipsychotic
drug prescription.
Treatment
There is no standard treatment for TD. The primary
approach is to discontinue or minimize the use of
antipsychotic drugs while attempting to treat some of the
symptoms. The treatment must be individualized to the
patient, because discontinuation of the antipsychotic
drug(s) may not be advisable, depending on the patient’s
condition. In some cases, substituting another drug for
the antipsychotic drug may be beneficial.
Prognosis
Once TD appears in full-blown form, it can be
per-manent. With careful management, some symptoms may
improve and even disappear with time. In less severe
cases, some patients may recover from TD within three
months of discontinuing the use of antipsychotic
medica-tion. Studies report that at least half of patients
experi-ence remission of major symptoms within 12 to 18
months following discontinuation of antipsychotic drugs.
In some patients, however, decreasing the dose of the
antipsychotic drug actually increases the symptoms of
TD, while increasing the dose sometimes offers a
tempo-rary remission of the symptoms.
Prevention
TD can be prevented by early recognition and
dis-continuation of the antipsychotic medication if this is
clinically possible. The use of antipsychotic drugs
should in any case be kept to a minimum in all patients.
Patients should be followed carefully to determine when
Ta
rd
iv
e d
the dose of the drug can be tapered off as the psychiatric
condition improves. In all cases, the benefits of taking
the antipsychotic medication should outweigh the risk of
developing TD.
A study has shown that elderly institutionalized
patients with
dementia
that were treated with
risperi-done had a low incidence of TD. Although further study
is needed, this study shows that non-conventional
neu-roleptic drugs should be considered to avoid the risk of
tardive dyskinesia, particularly in elderly patients.
Resources
BOOKS
Tasman, Allan. Psychiatry.Philadelphia: W.B. Saunders Com-pany, 1997.
Tierney, Lawrence, et al. Current Medical Diagnosis and
Treatment.Los Altos: Lange Medical Publications, 2001.
PERIODICALS
“Risperidone May Lower Incidence of TD.”Brown University
geroPsych Report(August 2000):2.
ORGANIZATIONS
National Institute for Mental Health. 6001 Executive Blvd., Room 8184, MSC 9663, Bethesda, MD 20892-9663. <http://www.nimh.nih.gov>.
Tardive Dyskinesia/Tardive Dystonia National Association. P.O. Box 45732, Seattle, WA 98145-0732. (206) 522-3166.
