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Dizziness - Hope Through Research
Most of us can remember feeling dizzy--after a roller coaster ride,
maybe, or when looking down from a tall building, or when, as children,
we would step off a spinning merry-go-round. Even superbly conditioned
astronauts have had temporary trouble with dizziness while in space. In
these situations, dizziness arises naturally from unusual changes that
disrupt our normal feeling of stability.
But dizziness can also be a sign that there is a disturbance or a
disease in the system that helps people maintain balance. This system is
coordinated by the brain, which reacts to nerve impulses from the ears,
the eyes, the neck and limb muscles, and the joints of the arms and
legs. If any of these areas fail to function normally or if the brain
fails to coordinate the many nerve impulses it receives, a person may
feel dizzy. The feeling of dizziness varies from person to person and,
to some extent, according to its cause; it can include a feeling of
unsteadiness, imbalance, or even spinning.
Disease-related dizziness, whether it takes the form of unsteadiness or
spinning, is fairly common in the older population. Today, both older
and younger people with serious dizziness problems can be helped by a
variety of techniques--from medication to surgery to balancing
exercises. Such techniques have been developed and improved by
scientists studying dizziness.
Much of today's research on dizziness is supported by the National
Institute Of Neurological and Communicative Disorders and Stroke
(NINCDS). This Institute is a unit of the National Institutes of Health.
It is the focal point within the Federal Government for research on the
brain and central nervous system, including studies of the senses
through which we interact with our surroundings.
With NINCDS support, scientists are searching for better ways to
diagnose and treat dizziness, and are investigating the mechanisms that
help us maintain our normal sense of balance. These studies, along with
basic research on how the ear, the brain, and the nerves work, hold the
best hope for relief for dizziness sufferers.
A delicate balancing act
To understand what goes wrong when we feel dizzy, we need to know about
the vestibular system by which we keep a sense of balance amid all our
daily twisting and turning, starting and stopping, jumping, falling,
rolling, and bending.
The vestibular system is located in the inner ear and contains the
following structures: vestibular labyrinth, semicircular canals,
vestibule, utricle, and saccule. These structures work in tandem with
the vestibular areas of the brain to help us maintain balance.
The semicircular canals and vestibule of the inner ear contain a fluid
called endolymph that moves in response to head movement.
The vestibular labyrinth is located behind the eardrum. The labyrinth's
most striking feature is a group of three semicircular canals or tubes
that arise from a common base. At the base of the canals is a rounded
chamber called the vestibule. The three canals and the vestibule are
hollow and contain a fluid called endolymph which moves in response to
Within the vestibule and the semicircular canals are patches of special
nerve cells called hair cells. Hair cells are also found in two
fluid-filled sacs, the utricle and saccule, located within the vestibule
These cells are aptly named: rows of thin, flexible, hairlike fibers
project from them into the endolymph.
Also located in the inner ear are tiny calcium stones called otoconia.
When you move your head or stand up, the hair cells are bent by the
weight of the otoconia or movement of the endolymph. The bending of the
hair cells transmits an electrical signal about head movement to the
brain. This signal travels from the inner ear to the brain along the
eighth cranial nerve--the nerve involved in balance and hearing. The
brain recognizes the signal as a particular movement of the head and is
able to use this information to help maintain balance.
In the inner ear, rows of hairlike fibers project from tiny patches of
nerve cells called hair cells.
These tiny calcium stones called otoconia are part of the inner ear's
A thorough exam reveals the cause of most dizziness.
The senses are also important in determining balance. Sensory input from
the eyes as well as from the muscles and joints is sent to the brain,
alerting us that the path we are following bends to the fight or that
our head is tilted as we bend to pick up a dime. The brain interprets
this information--along with cues from the vestibular system--and
adjusts the muscles so that balance is maintained.
Dizziness can occur when sensory information is distorted. Some people
feel dizzy at great heights, for instance, partly because they cannot
focus on nearby objects to stabilize themselves. When one is on the
ground, it is normal to sway slightly while standing. A person maintains
balance by adjusting the body's position to something close by. But when
someone is standing high up, objects are too far away to use to adjust
balance. The result can be confusion, insecurity, and dizziness, which
is sometimes resolved by sitting down.
Some scientists believe that motion sickness, a malady that affects sea,
car; and even space travelers, occurs when the brain receives
conflicting sensory information about the body's motion and position.
For example, when someone reads while riding in a car, the inner ear
senses the movement of the vehicle, but the eyes gaze steadily on the
book that is not moving. The resulting sensory conflict may lead to the
typical symptoms of motion sickness: dizziness, nausea, vomiting, and
Another form of dizziness occurs when we turn around in a circle quickly
several times and then stop suddenly. Turning moves the endolymph. The
moving endolymph tells us we are still rotating but our other senses say
we've stopped. We feel dizzy.
Diagnosing the problem
The dizziness one feels after spinning around in a circle usually goes
away quickly and does not require a medical evaluation. But when
symptoms appear to be caused by an underlying physical problem, the
prudent person will see a physician for diagnostic tests. According to a
study supported by the National Institute of Neurological and
Communicative Disorders and Stroke, a thorough examination can reveal
the underlying cause of dizziness in about 90 percent of cases.
A person experiencing dizziness may first go to a general practitioner
or family physician; between 5 and 10 percent of initial visits to these
physicians involve a complaint of dizziness. The patient may then be
referred either to an ear specialist (otologist) or a nervous system
As part of a research study, this NINCDS physician tests a patient's
balance. Tests that make the patient feel dizzy help establish a diagnosis.
The patient will be asked to describe the exact nature of the dizziness,
to give a complete history of its occurrence, and to list any other
symptoms or medical problems. Patients give many descriptions of
dizziness-depending to some extent on its cause. Common complaints are
light-headedness, a feeling of impending faint, a hallucination of
movement or motion, or a loss of balance without any strange feelings in
the head. Some people also report they have vertigo--a form of dizziness
in which one's surroundings appear to be spinning uncontrollably or one
feels the sensation of spinning.
The physician will try to determine what components of a patient's
nervous system are out of kilter, looking first for changes in blood
pressure, heart rhythm, or vision--all of which may contribute to the
complaints. Sometimes dizziness is associated with an ear disorder. The
patient may have loss of hearing, discomfort from loud sounds, or
constant noise in the ear, a disorder known as tinnitus. The physician
will also look for other neurological symptoms: difficulty in swallowing
or talking, for example, or double vision.
Tests and scans
After the initial history-taking and physical examination, the physician
may deliberately try to make the patient feel dizzy. The patient may be
asked to repeat actions or movements that generally cause dizziness: to
walk in one direction and then turn quickly in the opposite direction,
or to hyperventilate by breathing deeply for 3 minutes.
In another test, the patient sits upright on an examining table. The
physician tilts the patient's head back and turns it partway to one
side, then gently but quickly pushes the patient backward to a lying
down position. The reaction to this procedure varies according to the
cause of dizziness. Patients with benign positional vertigo may
experience vertigo plus nystagmus. rapid, uncontrollable back-and-forth
movements of the eyes.
In a new caloric test to diagnose dizziness, air or water is injected
gradually into a patient's ears. The eye movements that result are
One widely used procedure, called the caloric test, involves electronic
monitoring of the patient's eye movements while one ear at a time is
irrigated with warm water or warm air and then with cold water or cold
air. This double stimulus causes the endolymph to move in a way similar
to that produced by rotation of the head. If the labyrinth is working
normally, nystagmus should result. A missing nystagmus reaction is a
strong argument that the balance organs are not acting correctly.
NINCDS-supported scientists at The Johns Hopkins University in Baltimore
observed that not all patients can tolerate the traditional caloric
test. Some become sick when the ear is irrigated with the standard
amount of water or air before physicians can measure their eye
movements. So the scientists are designing a method of conducting the
test more gradually by slowly adjusting the amount of water or air
reaching the inner ear. Their goal is to reduce patient discomfort while
allowing the test to proceed.
Balance disorders are often accompanied by hearing loss.
Some patients who cannot tolerate the caloric test are given a rotatory
test. In this procedure, the patient sits in a rotating chair, head
tilted slightly forward. The chair spins rapidly in one direction, then
stops abruptly. Depending on the cause of dizziness, the patient may
experience vertigo after this rotation.
In one variation of this test, the chair is placed in a tent of striped
cloth. As the chair rotates, electrodes record movements of the
patient's eyes in response to the stripes. The physician evaluates these
eye movements, a form of nystagmus, to determine if the patient has a
disorder of the balance system.
Because disorders of balance are often accompanied by hearing loss, the
physician may order a hearing test.
Hearing loss and associated dizziness could also be due to damaged nerve
cells in the brain stem, where the hearing and balance nerve relays
signals to the brain. To detect a malfunction, the physician may order a
kind of computerized brain wave study called a brain stem auditory
evoked response test. In this procedure, electrodes are attached to
several places on the surface of the patient's scalp and a sound is
transmitted to the patient's ear. The electrodes measure the time it
takes nerve signals generated by the sound to travel from the ear to the
Patients with dizziness may undergo a computed tomographic (CT) scan to
see if the problem is a tumor or a cyst.
If there is reason to suspect that the dizziness could stem from a tumor
or cyst, the patient may undergo a computed tomographic (CT) scan. In a
CT scan, x-ray pictures are taken of the brain from several different
angles. These images are then combined by a computer to give a detailed
view that may reveal the damaging growth.
Sometimes anxiety and emotional upset cause a person to feel dizzy.
Certain patients may be asked to take a psychological test, to try to
find out whether the dizziness is caused or intensified by emotional
The many tests administered by a physician will usually point to a cause
for the patient's dizziness. Disorders responsible for dizziness can be
* peripheral vestibular, or those involving a disturbance in the
* central vestibular, or those resulting from a problem in the brain
or its connecting nerves.
* systemic, or those originating in nerves or organs outside the
When someone has vertigo but does not experience faintness or difficulty
in walking, the cause is probably a peripheral vestibular disorder. In
these conditions, nerve cells in the inner ear send confusing
information about body movement to the brain.
Meniere's disease. A well-known cause of vertigo is the peripheral
vestibular disorder known as Meniere's disease. First identified in 1861
by Prosper Meniere, a French physician, the disease is thought to be
caused by too much endolymph in the semicircular canals and vestibule.
Some scientists think that the excess endolymph may affect the hair
cells so that they do not work correctly. This explanation, however, is
still under study.
The vertigo of Meniere's disease comes and goes without an apparent
cause; it may be made worse by a change in position and reduced by being
In addition to vertigo, patients have hearing loss and tinnitus. Hearing
loss is usually restricted at first to one ear and is often severe.
Patients sometimes feel "fullness" or discomfort in the ear, and
diagnostic testing may show unusual sensitivity to increasingly loud
sounds. In 10 to 20 percent of patients, hearing loss and tinnitus
eventually occur in the second ear.
Patients suspected of having Meniere's disease commonly undergo
electronystagmography, an electronic recording of the caloric test.
Meniere's disease patients are often helped by drugs or surgery.
Meniere's disease patients may undergo electronystagmography, an
electrical recording of the caloric test, to determine if their
labyrinth is working normally.
Attacks of Meniere's disease may occur several times a month or year and
can last from a few minutes to many hours. Some patients experience a
spontaneous disappearance of symptoms while others may have attacks for
Treatment of Meniere's disease includes such drugs as meclizine
hydrochloride and the tranquilizer diazepam to reduce the feeling of
intense motion during vertigo. To control the buildup of endolymph, the
patient may also take a diuretic, a drug that reduces fluid production.
A low-salt diet--which reduces water retention-is claimed to be an
effective treatment of Meniere's disease.
When these measures fail to help, surgery may be considered. In shunt
surgery, part of the inner ear is drained to reestablish normal inner
ear fluid or endolymph pressure. In another operation, called vestibular
nerve section, surgeons expose and cut the vestibular part of the eighth
nerve. Both vestibular nerve section and shunt surgery commonly relieve
the dizziness of Meniere's disease without affecting hearing.
A more drastic operation, labyrinthectomy, involves total destruction of
the inner ear. This procedure is usually successful in eliminating
dizziness but causes total loss of hearing in the operated ear--an
important consideration since the second ear may one day be affected.
Positional vertigo. People with benign positional vertigo experience
vertigo after a position change. Barbara noticed the first sign of this
disorder one morning when she got up out of bed. She felt the room
spinning. Frightened, she quickly returned to bed and lay down. After
about 30 seconds the vertigo passed. Fearing a stroke, Barbara went to
the emergency room of a hospital for a medical evaluation, which failed
to show a problem. She had no symptoms for several days, then the
problem returned. At this point, Barbara was referred to an
otoneurologist, a physician who specializes in the ear and related parts
of the nervous system.
Viral infections may lead to vestibular neuronitis
Like Barbara, most patients with benign positional vertigo are extremely
worried about their symptoms. But the patients usually feel less
threatened once the disorder is diagnosed.
The cause of benign positional vertigo is not known, although some
patients may recall an incident of head injury. The condition can strike
at any adult age with attacks occurring periodically throughout a
In one type of treatment, the patient practices the position that
provokes dizziness until the balance system eventually adapts. Rarely, a
physician will prescribe medication to prevent attacks.
Vestibular neuronitis. In this common vestibular disorder, the patient
has severe vertigo. Jack experienced his first attack of this problem at
2 a.m. when he rolled over in bed and suddenly felt the room spinning
violently. He started vomiting but couldn't stand up; finally, he
managed to crawl to the bathroom. When he returned to bed, he lay very
still--the only way to stop the vertigo. Three days later, he was able
to walk without experiencing vertigo, but he still felt unsteady.
Gradually, over the next several weeks, Jack's balance improved, but it
was a year before he was entirely without symptoms.
Unlike Meniere's disease, vestibular neuronitis is not associated with
hearing loss. Patients with vestibular neuronitis first experience an
acute attack of severe vertigo lasting for hours or days, just as Jack
did, with loss of balance sometimes lasting for weeks or months. About
half of those who have a single attack have further episodes over a
period of months to years.
The cause of vestibular neuronitis is uncertain. Since the first attack
often occurs after a viral illness, some scientists believe the disorder
is caused by a viral infection of the nerve.
Other labyrinth problems. Inner ear problems with resulting dizziness
can also be caused by certain antibiotics used to fight life-threatening
bacterial infections. Probably the best-known agent of this group is
streptomycin. Problems usually arise when high doses of these drugs are
taken for a long time, but some patients experience symptoms after short
treatment with low doses, especially if they have impaired kidneys.
The first symptoms of damage to the inner ear caused by medication are
usually hearing loss, tinnitus, or unsteadiness while walking. Stopping
the drug can usually halt further damage to the balance mechanism, but
this is not always possible: the medicine may have to be continued to
treat a life-threatening infection. Patients sometimes adapt to the
inner ear damage that may-occur after prolonged use of these antibiotics
and recover their balance
Balance can also be affected by a cholesteatoma, a clump of cells from
the eardrum that grow into the middle ear and accumulate there These
growths are thought to result from repeated infections such as recurrent
otitis media. If unchecked, a cholesteatoma can enlarge and threaten the
inner ear. But if the growth is detected early, it can be surgically
Brain and nerve damage
The vestibular nerve carries signals from the inner ear to the brain
stem. If either the nerve or the brain stem is damaged, information
about position and movement may be blocked or incorrectly processed,
leading to dizziness. Conditions in which dizziness results from damage
to the brain stem or its associated nerves are called central causes of
Acoustic neuroma. One central cause of dizziness is a tumor called an
acoustic neuroma. Although the most common sign of this growth is
hearing loss followed by tinnitus, some patients also experience
An acoustic neuroma usually occurs in the internal auditory canal, the
bony channel through which the vestibular nerve passes as it leaves the
inner ear. The growing tumor presses on the nerve, sending false
messages about position and movement to the brain.
The hearing nerve running alongside the vestibular nerve can also be
compressed by the acoustic neuroma, with resulting tinnitus and hearing
loss. Or the tumor may press on other nearby nerves, producing numbness
or weakness of the face. If the neuroma is allowed to grow, it will
eventually reach the brain and may affect the function of other cranial
These benign cells from an acoustic neuroma were grown in tissue
culture. If diagnosed early, acoustic neuromas can be removed completely
with no neurological damage.
Early treatment of acoustic neuroma helps patients regain balance.
Computed tomography has revolutionized the detection of acoustic
neuromas. If an early diagnosis is made, a surgeon can remove the tumor.
The patient usually regains balance.
Dizziness may be a sign of a "small stroke" or transient
ischemic attack (TIA) in the brain stem. TIA's, which result from a
temporary lack of blood supply to the brain, may also cause transient
numbness, tingling, or weakness in a limb or on one side of the face.
Other signs include temporary blindness and difficulty with speech.
These symptoms are warning signs: one should see a physician immediately
for treatment. If a TIA is ignored, a major stroke may follow.
Systemic diseases: underlying illness
Dizziness can be a symptom of diseases affecting body parts other than
the-brain and central nervous system. Systemic conditions like anemia or
high blood pressure decrease oxygen supplies to the brain; a physician
eliminates the resulting dizziness by treating the underlying systemic
Damaged sensory nerves. We maintain balance by adjusting to information
transmitted along sensory nerves from sensors in the eyes, muscles, and
joints to the spinal cord or brain. When these sensory nerves are
damaged by systemic disease, dizziness may result.
Multiple sensory deficits, a systemic disease, is believed by some
physicians to be the chief cause of vaguely described dizziness in the
aged population. In this disorder several senses or sensory nerves are
damaged. The result: faulty balance.
People with diabetes, which can damage nerves affecting vision and
touch, may develop multiple sensory deficits. So can patients with
arthritis or cataracts, both of which distort how sensory information
reaches the brain. The first step in treating multiple sensory deficits
is to eliminate symptoms of specific disorders. Permanent contact lenses
can improve vision in cataract patients, for example, and medication or
surgery may ease pain and stiffness related to arthritis.
Symptoms of damaged sensory nerves may be relieved by a collar to
eliminate extreme head motion, balancing exercises to help compensate
for sensory losses, or a cane to aid balance. Some patients are helped
by the drug methylphenidate, which can increase awareness of remaining
Systemic neurological disorders such as multiple sclerosis, Alzheimer's
disease, Parkinson's disease, or Creutzfeldt-Jakob disease may also
cause dizziness, primarily during walking. However, dizziness is rarely
the sole symptom of these nervous system diseases.
Low blood pressure. One common systemic disease causing dizziness is
postural or orthostatic hypotension. In this disease, the heart does not
move the blood with enough force to supply the brain adequately.
Symptoms include sudden feelings of faintness, light-headedness, or
dizziness when standing up quickly.
Because the muscles in aging blood vessels are weak and the arteries
inadequate in helping convey blood to the head, older people are
particularly susceptible to this condition. Older persons who do not sit
or lie down at the first sensation of dizziness may actually lose
Postural hypotension is easily diagnosed. The patient's blood pressure
is checked before standing abruptly and immediately afterward.
Anxiety can trigger attacks of dizziness
People who have undetected anemia or those who are taking diuretics to
eliminate excess water from their body and reduce high blood pressure
are also at risk of developing postural hypotension.
A physician can easily diagnose postural hypotension: the patient's
blood pressure is measured before standing abruptly and immediately
afterward. Treatment is designed to eliminate dizziness by reducing the
patient's blood volume.
A secondary symptom
Dizziness may also be a secondary symptom in many
other diseases. Faintness accompanied by occasional loss of
consciousness can be due to low blood sugar, especially when the faint
feeling persists after the patient lies down.
A common cause of mild dizziness--the kind described as
light-headedness--is medicine. A number of major prescription drugs may
produce light-headedness as a side effect. Two types of drugs that can
cause this problem are sedatives, which are taken to induce sleep, and
tranquilizers, which are used to calm anxiety.
When anxiety strikes
Tranquilizers may cause a type of dizziness referred to as
light-headedness--but so may anxiety. Cynthia is a young woman who
becomes light-headed under a variety of stressful circumstances. The
light-headedness sometimes is accompanied by heart palpitations and
panic. She can produce these symptoms at will by breathing rapidly and
deeply for a few minutes.
Cynthia's light-headedness is due to hyperventilation: rapid, prolonged
deep breathing or occasional deep sighing that upsets the oxygen and
carbon dioxide balance in the blood. The episodes are typically brief
and often associated with tingling and numbness in the fingers and
around the mouth. Hyperventilation is triggered by anxiety or depression
in about 60 percent of dizziness patients.
Research offers new insights into the basis of balance
Once made aware of the source of the symptoms, a patient can avoid
hyperventilation or abort attacks by breath-holding or breathing into a
paper bag to restore a correct balance of oxygen and carbon dioxide. If
hyperventilation is due to anxiety, psychological counseling may be
Some patients who report dizziness may be suffering from a psychiatric
disorder. Generally these persons will say that they experience
light-headedness or difficulty concentrating; they may also describe
panic states when in crowded places. Tests of such patients reveal that
the inner ear is working correctly. Treatment may include counseling.
Demystifying dizziness through research
Scientists are working to understand dizziness and its sources among the
complex interactions of the labyrinth, the other sense organs, and the
brain. The research is offering new insights into the basis of balance,
as well as improvements in diagnosis, treatment, and prevention of
Innovative surgery. Delicate surgical instruments and operating
microscopes have made possible new methods to help patients with
dizziness. The symptoms of benign positional vertigo, for example, may
be relieved by a microsurgical ear operation called a singular
neurectomy in which a tiny portion of the vestibular nerve is divided
Patients with Meniere's disease may benefit from a microsurgical
operation called the cochleosacculotomy. In this procedure, a small
curette or wire loop is used to reach into the vestibule of the inner
ear and remove the fluid-filled saccule. An investigator at the
Massachusetts Eye and Ear Institute in Boston has found that this
operation relieves symptoms of vertigo in about 80 percent of patients.
Space biology. Research also promises to help astronauts who suffer from
dizziness or space sickness. In one study, a scientist aboard a space
shuttle conducted experiments to find out why half the astronauts who
have space sickness at the start of a flight overcome this problem
before the end of the mission. The investigator, from the Massachusetts
Institute of Technology, found that the space traveler's brain no longer
relies on the gravity-sensitive inner ear structures for information
about position and motion. Instead, the astronaut's brain realizes that
the inner ear is sending false information and starts to depend more on
the eyes to find out about the body's movements. This finding may enable
space biologists to train astronauts before launch to avoid space
During that same space mission, a German scientist performed experiments
that raised questions about the theory behind the caloric test.
According to that theory, alternate heating and cooling of the endolymph
causes the fluid to form wave-like swirling patterns called convection
currents. These currents make the brain think the head is moving. The
result is nystagmus.
In space, however, lack of gravity should prevent convection currents
from forming, so the eyes were expected to remain still. Instead, they
moved just as though the test was being done on Earth in normal gravity.
These experiments indicate there is more than one explanation for why
the caloric test works: when the endolymph is warmed, the fluid expands
and moves the cupula, the top of the cochlear duct. The movement of the
cupula cues the brain that the head is moving and the eyes respond.
This research helps scientists interpret methods used to test vestibular
function. It also promises to increase our understanding of the balance
Currently, scientists at the Johnson Space Center in Houston and at the
Good Samaritan Hospital in Portland are preparing to study space
sickness and vestibular function in a microgravity (near zero gravity)
laboratory. The astronauts' vestibular function will be analyzed in a
series of experiments, including studies to test whether visual input
becomes more important in maintaining balance as weightlessness
increases. The scientists anticipate that this research will help all
sufferers of motion sickness, not just astronauts.
Scientists are developing better diagnostic tests for dizziness
Improved diagnosis. Back on Earth, improvements are being made in
measuring precisely the eye movements of patients undergoing diagnostic
tests for dizziness. Investigators at the NINCDS-funded research center
at the University of California at Los Angeles have developed a
computer-controlled chair in which a patient is shifted into a variety
of body positions to stimulate the labyrinth. Eye responses are measured
with newly designed computerized instruments. To further stimulate eye
movements, a set of computer-generated visual patterns can be moved with
the chair or independently. of it.
These instruments will extract much information about a patient's
ability to integrate information from the eyes and the inner ear, and
will help distinguish patients with different disorders of the balance
Signaling the brain. To understand dizziness, scientists must find out
how stimuli to the labyrinth are translated into information that the
brain can use to maintain balance. How, for example, is information from
the inner ear sent to the brain and interpreted? Among the scientists
studying this question is an NINCDS grantee at the University of Chicago
who is looking at the different ways hair cells react to the movement of
inner ear fluid. He has identified a characteristic pattern of
electrical response in hair cells. The next step is to discover how
these messages are interpreted by the nerve cells carrying information
to the brain.
An NINCDS grantee at the University of Minnesota adjusts the controls on
an oscilloscope used to monitor patients' eye movements during
Another NINCDS grantee at the University of Minnesota is studying the
activity of the brain when it sends balance-preserving signals from the
sense organs to the muscles. In one experiment, healthy persons are
rotated in the dark at a constant rate. After a few minutes they no
longer think they are moving. This is because the inner ear only senses
changes in the rate of movement. If the lights are turned on and both
the chair and the room rotate at the same constant speed, again the
person doesn't sense movement. Both the inner ear and the eyes are
fooled into thinking there is no motion.
But the investigator found that if the chair and the room are
accelerated, the patient develops what is described as sensory conflict.
The acceleration of the chair tells the inner ear that there is
movement. But the eyes tell the brain that the body is stationary. How
patients react in these conflict situations reveals how the brain puts
together various types of sensory information to maintain balance. The
results of this and related experiments will help scientists build a
mathematical model of the balance system.
Hope for the future
For those who are healthy, equilibrium is a sense often taken. for
granted. People can't see their labyrinth, even though it is as much a
sense organ as the ears or the eyes. But when it is injured, an ability
vital to everyday living is lost.
Scientists already understand a great deal about the labyrinth's
function and the way the brain maintains balance. Further research into
this complex system should help those who are incapacitated by dizziness
when the balance system goes awry.
Voluntary health organizations
The following organizations provide information on dizziness or on inner
ear diseases that cause dizziness:
Acoustic Neuroma Association
P.O. Box 398
Carlisle, PA 17013
American Academy of Otolaryngology-Head and
1101 Vermont Avenue, N.W.
Washington, DC 20005
Better Hearing Institute
P.O. Box 1840
Washington, DC 20013
(800) 424-8576 (Toll free)
National Hearing Association
Oak Brook, IL 60521
Human tissue banks
The study of ear tissue from patients with dizziness and deafness is
invaluable in research. Temporal bones willed by people with balance or
hearing problems and by people with normal hearing can be used to help
research scientists and physicians training to be otolaryngologists.
Physicians in training study the basic anatomy of the temporal bone and
develop their surgical skills. Scientists use the bones for research on
the inner ear and on congenital disorders that cause deafness. Middle
ear bones (ossicles) and the eardrum are also used as grafts to
surgically correct sound transmission problems of the middle ear.
NINCDS supports four temporal bone banks that supply scientists in every
state with tissue from patients who have dizziness or deafness. The
donated temporal bone includes the eardrum, the entire middle and inner
ear, and the nerve tissues which combine into the brain stem. For
information about tissue donation and collection, write to:
National Temporal Bone Bank
Massachusetts Eye and Ear Infirmary
243 Charles Street
Boston, MA 02114
(617) 523-7900, ext. 2711
National Temporal Bone Bank
University of Minnesota
Minneapolis, MN 55455
National Temporal Bone Bank
Baylor College of Medicine
Neurosensory Center--Room A523
Houston, TX 77030
National Temporal Bone Bank
UCLA School of Medicine
31-24 Rehabilitation Center
Los Angeles, CA 90024
Some useful definitions:
acoustic neuroma: tumor of the vestibular nerve that may press on the
hearing nerve causing dizziness and hearing loss.
balance system: complex biological system that enables us to know where
our body is in space and to keep the position we want. Proper balance
depends on information from the labyrinth in the inner ear, from other
senses such as sight and touch, and from muscle movement.
benign positional vertigo: condition in which moving the head to one
side or to a certain position brings on vertigo.
brain stem auditory evoked response (BAER): diagnostic test in which
electrodes are attached to the surface of the scalp to determine the
time it takes inner ear electrical responses. to sound to travel from
the ear to the brain. The test helps locate the cause of some types of
caloric test: diagnostic test in which warm or cold water or air is put
into the ear. If a person experiences certain eye movements (nystagmus)
after this procedure, the labyrinth is working correctly.
cholesteatoma: a tumorlike accumulation of dead cells in the middle ear.
This growth is thought to result from repeated middle ear infections.
computed tomography (CT) scan: radiological examination useful for
examining the inside of the ear and head.
diuretic: drug that promotes water loss from the body, through the
urine. Used to treat hypertension, diuretics may bring on dizziness due
to postural hypotension.
dizziness: feeling of physical instability with regard the outside
endolymph: fluid filling part of the labyrinth.
hair cells: specialized nerves found in the semicircular canals and
vestibule. Fibers (hairs) sticking out of one end of the hair cells move
when the head moves and send information to the brain that is used to
hyperventilation: repetitive deep breathing that reduces the carbon
dioxide content of the blood and brings on dizziness. Anxiety may cause
hyperventilation and dizziness.
inner ear: contains the organs of hearing and balance.
labyrinth: the organ of balance, which is located in the inner ear. The
labyrinth consists of the three semicircular canals and the vestibule.
Meniere's disease: condition that causes vertigo. The disease is
believed to be caused by too much endolymph in the labyrinth. Persons
with this illness also experience hearing problems and tinnitus.
middle ear: the space immediately behind the eardrum. This part of the
ear contains the three bones of heating: the hammer (malleus), anvil
(incus), and stirrup (stapes).
multiple sensory deficits: condition associated with dizziness in which
damage to nerves of the eye and arms or legs reduces information about
balance to the brain.
neurologist: physician who specializes in disorders of the nervous
nystagmus: rapid back-and-forth movements of the eyes. These reflex
movements may occur during the caloric test and are used in the
diagnosis of balance problems.
orthostatic hypotension: see postural hypotension.
otologist: physician who specializes in diseases of the ear.
peripheral vestibulopathy: vestibular disorder in which the vestibular
nerve appears inflamed and paralyzed. Patients may have one or several
attacks of vertigo.
postural hypotension (also called orthostatic hypotension): sudden
dramatic drop in blood pressure when a person rises from a sitting,
kneeling, or lying position. The prime symptom of postural hypotension,
which is sometimes due to low blood volume, is dizziness or faintness.
The condition can be dangerous in older persons, who may faint and
semicircular canals: three curved hollow tubes in the inner ear that are
part of the balance organ, the labyrinth. The canals are joined at their
wide ends and are filled with endolymph.
stroke: death of nerve cells due to a loss of blood flow in the brain. A
stroke often results in permanent loss of some sensation or muscle
TIA: see transient ischemic attack.
tinnitus: noises or ringing in the ear.
transient ischemic attack (TIA): temporary interruption of blood flow to
a part of the brain. Because a TIA may signal the possibility of a
stroke, it requires immediate medical attention. During a TIA, a person
may feel dizzy, have double vision, or feel tingling in the hands.
vertigo: severe form of dizziness in which one's surroundings appear to
be spinning uncontrollably. Extreme cases of vertigo may be accompanied
vestibular disorders: diseases of the inner ear that cause dizziness.
vestibular nerve: nerve that carries messages about balance from the
labyrinth in the inner ear to the brain.
vestibular neuronitis: another name for peripheral vestibulopathy.
vestibule: part of the labyrinth, located at the base of the
semicircular canals. This structure contains the endolymph and patches
of hair cells.
While a patient watches a rotating drum, the otoneurologist checks his
eyes for signs of any disturbance in neurological function that could
Information provided by the NIH.