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Let’s talk Vestibular Dysfunction

Dizziness is a general term that describes sensations of imbalance and unsteadiness, such as vertigo, mild turning, imbalance, and near fainting or fainting. Feelings of dizziness stem from the vestibular system, which includes the brain and the parts of the inner ear that sense position and motion, coupled with sensory information from the eyes, skin, and muscle tension.

Because dizziness is a general term for a variety of feelings of instability, it spans a large range of symptoms. These symptoms range from the most dramatic, vertigo, to the least severe, imbalance. Included in these feelings is fainting, which results in a loss of consciousness.

Vertigo is an acute feeling of violent rotation. People with vertigo often feel as if they are tilting or falling through space. Vertigo is most often caused by problems with the vestibular system of the inner ear. Symptoms can be brief, or may last for extended periods of time and may be accompanied by changes in pulse and blood pressure, perspiration, nausea, and a type of rapid eye movement called nystagmus.

Mild turning is a less violent type of vertigo. People with mild turning are still able to function in normal daily routines. However, a feeling of turning may continue for weeks. Mild turning is usually a symptom of inner ear dysfunction. It may also result from transient ischemic attack , or a lack of blood flow to the brain. People who have suffered from strokes may feel mild turning for periods of time. Mild turning may also be associated with multiple sclerosis , AIDS , or head trauma.

Imbalance is a feeling of instability or floating. It is associated with many general medical problems such as the flu or infection. Imbalance can also be associated with arthritis, especially in the neck, or another neurological problem.

Fainting is a sudden loss of consciousness and near fainting is a feeling of extreme light-headedness with a sinking or falling feeling. Vision usually becomes hazy or dimmed and the extremities become weak. Both fainting and near fainting are caused by lack of blood flow to the brain. Anything that causes a rapid drop in blood pressure, such as a heart attack or an insulin reaction in a diabetic, can result in fainting or near fainting. Panic attacks that cause a person to exhale a lot of carbon dioxide can cause fainting or near fainting.
Vestibular system

The vestibular system is the sensory system located in the inner ear that helps the body to maintain balance. Balance in the human body is coordinated by the brainstem, which, with speed and precision, collects information from other parts of the brain and sensory organs throughout the body. It is the brainstem that sends neurological instructions to the muscles and joints. The sensory organs that play critical roles relaying information to the brain-stem include the skin, eyes, muscles and joints, and the vestibular system in the inner ear. Dizziness may result with dysfunction in any of these components or in the nerves that connect them.

The cerebellum , which is responsible for coordination and the cerebral cortex, provides neurological information to the brainstem. For example, the cerebellum is the organ that informs the body how to shift weight when going down a flight of stairs and how to balance on a bicycle. These processes are accomplished without conscious thinking.

In order to maintain balance, the brainstem depends on input from sensory organs including the eyes, muscles, joints, skin and ears. This information is relayed to the brainstem via the spinal cord. The combined neurological receptor system, which involves the brainstem, spinal cord, and sensory organs, is called the proprioceptive system. Proprioceptive dysfunction may result in dizziness, and people with problems with their proprioceptive system may fall often. Additionally, as people age, problems with proprioception become more common.
Sensory organs

Visual information is of particular importance to maintaining balance. The visual systems most involved are the optokinetic and pursuit systems. The optokinetic system is the motor impulse responsible for moving the eyes when the head moves, so that the field of vision remains clear. The pursuit system allows a person to focus on a moving object while the head remains stationary. Both of these systems feed information about the person’s position relative to the surroundings to the brainstem. A specific type of eye movement called nystagmus, which is repetitive jerky movements of the eye, most often in the horizontal direction, may cause dizziness. Nystagmus may indicate that neurologic signals from the optokinetic or pursuit systems are not in agreement with the other balance information received by the brain.

Sensory information from muscles, joints, and skin plays a key role in balance. The muscles and joints of the human body are lined with sensory receptors that send neurological information about the position of the body to the brainstem. For example, receptors in the neck muscles tell the brain which way the head is turned. The skin, in particular the skin of the feet and buttocks, is covered with pressure sensors that relay information to the brain regarding what part of the body is touching the ground.
Peripheral vestibular system

The ear, particularly the inner ear, plays a critical role in maintaining balance. The inner ear contains two major parts: the cochlea, which is mostly used for hearing, and the vestibular apparatus, also known as the peripheral vestibular system, which is important in balance. A set of channels connects the two parts of the ear and therefore any disease that affects hearing may also affect balance, and vice versa.

The peripheral vestibular system consists of a series of canals and chambers, all of which are made of membranes. This membrane system is filled with a fluid called endolymph. The peripheral vestibular system is further embedded in the temporal bone of the skull. In the space between the temporal bone and the membranes of the peripheral vestibular system resides a second fluid called perilymph. Endolymph and perilymph each have a different chemical makeup consisting of varying concentrations of water, potassium, sodium, and other salts. Endolymph flows out of the peripheral vestiubular system into an endolymphatic sac and then diffuses through a membrane into the cerebrospinal fluid that bathes the brain. Peri-lymph flows out of the peripheral vestibular system and directly into the cerebrospinal fluid. When the flow pressures or chemical compositions of the endolymph and perilymph change, feelings of dizziness can occur. These types of changes may be related to Mèniére’s disease.

The vestibular apparatus is made up of two types of sensory organs: otolith organs and semicircular canals. The otolith organs sense the direction of gravity, while the semi-circular canals sense rotation and movement of the head.

Two otolith organs in each ear are called the saccule and the utricle. The saccule is oriented in a vertical direction when a person is standing and, best senses vertical motion of the head. The utricle is nearly horizontal when a person is standing, so it best senses horizontal motion of the head. Each organ consists of calcium carbonate crystals embedded in a gel. Special hair-producing cells extend into the gel from below. As the head moves, gravity and inertia cause the crystals to bend the hairs, which are in contact with nerves. Information on the position and motion of the head is thus relayed to the brain. If the hairs or the crystals in the otolith organs are damaged, feelings of dizziness may result.

In each ear, there are also three semicircular canals that lie on planes that are perpendicular to each other. The canals are connected together by a main chamber called a vestibule. The canals and the vestibule are filled with endolymph fluid. Near its connection to the vestibule, one end of each of the canals widens into a region called the ampulla. One side of the ampulla is lined with specialized sensory cells. These cells have hairlike structures that extend into a gelatinous structure called a cupula. As the head moves in a given plane, the endolymph inside the semicircular canal in that plane remains stationary due to inertia. The cupula, however, moves because it is attached to the head. This puts pressure on the cupula, which in turn moves the hairlike structures. The bending of the hairlike structures stimulates nerves, alerting the brain that the head is moving in a particular plane. By integrating information from all three planes in which the semicircular canals lie, the brain reconstructs the three-dimensional movement of the head. If information from one of the semicircular canals does not agree with that of another, or if the information generated by semicircular canals in one ear does not agree with the information produced by the other ear, feelings of dizziness may result.

All of the signals from the peripheral vestibular system travel to the brain along the eighth cranial nerve, also called the vestibular nerve. Damage to this nerve, either through head trauma or the growth of tumors, can also cause feelings of dizziness. Neurological information from the semicircular canals seems be more important to the brain than information from the otolith structures. If the eighth cranial nerve on one side of the head is damaged, but the other side remains intact, the brain learns to compensate over time; however, the mechanics involved in this process are not well understood.

Dizziness is an extremely common symptom occurring in people of all ages, ethnicities, and socioeconomic backgrounds. Balance disorders increase with age, and by age 75, dizziness is one of the most common reasons for visiting a doctor. In the general population, dizziness is the third most common reason that patients visit doctors. According to the National Institutes of Health (NIH), about 42% of the population of the United States will complain of dizziness at some point in their lives. In the United States, the cost of medical care for patients with symptoms of imbalance is estimated to be more than $1 billion per year.
Diseases associated with dizziness

Because it involves so many different parts of the body, the balance system may exhibit signs of dysfunction for a variety of reasons. Dizziness may be caused by problems with the central nervous system , the vestibular system, the sensory organs, including the eyes, muscles and joints, or more systemic disorders such as cardiovascular disease, bacterial and viral diseases, arthritis, blood disorders, medications, or psychological illnesses.
Central nervous system dysfunction

Any problem that affects the nerves leading to the brain from vestibular or sensory organs, the spinal cord, the cerebellum, the cerebral cortex, or the brainstem may result in dizziness. In particular, tumors that affect any of these organs are of concern. In addition, disorders that affect blood supply to the central nervous system, such as transient ischemic attacks, stroke , migraines, epilepsy , or multiple sclerosis, may result in feelings of dizziness.

BRAINTUMORS Although rare, acoustic neuroma is a benign tumor growing on the vestibulo-cochlear nerves, which reach from the inner ear to the brain. It may press as well on blood vessels that flow between the peripheral vestibular system and the brain. Symptoms included ringing in one ear, imbalance, and hearing loss. Distortion of words often becomes increased as the tumor grows and disturbs the nerve. Treatment requires surgical removal of the tumor, which nearly always returns the sense of balance to normal, although some residual hearing loss may occur.

Other brain tumors may also cause feelings of dizziness. These include tumors that originate in the brain tissue, such as meningiomas (benign tumors) and gliomas (malignant tumors). Sometimes tumors from other parts of the body may metastasize in the brain and cause problems with balance.

CEREBRAL ATROPHY Age causes atrophy (deterioration) of brain cells that may result in slight feelings of imbalance. More severe forms of dizziness may result from other neurological disorders.

BLOOD SUPPLY DISORDERS If the blood flow and oxygenation to the cerebellum, cerebral cortex, or brain-stem is not adequate, feelings of dizziness can result. Such symptoms can result from several types of disorders, including anemia, transient ischemic attacks (TIAs), and stroke.

TIAs are temporary loss of blood supply to the brain, often caused by arteriosclerosis (hardening of the arteries). In addition to a brief period of dizziness or vertigo, symptoms include a transient episode of numbness on one side of the body, and slurred speech and/or lack of coordination. If the loss of blood supply to the brain is due to a blockage in one of the arteries in the neck, surgery may correct the problem.

Strokes, or cerebrovascular accidents (CVA), occur in three major ways. A thrombotic stroke occurs when a fatty deposit forms a clot in an artery, blocking blood supply to the brain. An embolic stroke occurs when part of a clot from another part of the body breaks off and obstructs an artery leading to the brain. A hemorrhagic stroke occurs when blood vessels in the brain hemorrhage, leaving a blood clot in the brain.

PERIPHERAL VESTIBULAR SYSTEM DYSFUNCTION When balance problems are brief or intermittent, the peripheral vestibular system is usually the cause. Many different problems may be at the root of vestibular disorder.

BENIGN PAROXYSMAL POSITIONAL VERTIGO (BPPV) Benign paroxysmal positional vertigo occurs following an abrupt change in position of the head. Often, onset of vertigo occurs when patients roll from their back onto the side, and it usually subsides in less than a minute. BPPV can result from head trauma, degeneration of the peripheral vestibular system with age, infection of the respiratory tract, high blood pressure, or other cardiovascular diseases. Those who suffer from an infection of their vestibular system, causing severe vertigo that lasts up to several days, can develop BPPV any time within the next eight years. BPPV is also associated with migraine headaches .

Two theories on the cause of BPPV currently exist. One suggests that BPPV will occur when the calcium carbonate crystals in the otolith organs (the saccule and the utiricle) are displaced and become lodged in the cupula of the semicircular canals due to head trauma, infection, or degeneration of the inner ear canals. This displacement will stimulate the nerves from the semicircular canals when the head rotates in a particular position, indicating to the brain that the person is spinning. However, the rest of the sensory organs in the body report that the body is stationary. This conflicting information produces vertigo. The calcium carbonate crystals dissolve after a brief time, and the symptom is rectified. The second theory suggests that cellular debris accumulates into a mass that moves around the semicircular canals, exerting pressure on the cupula and causing vertigo. When the mass dissolves, the symptoms subside.

INNER EAR INFECTIONS Inner ear infection, or vestibular neuronitis, occurs some time after a person has suffered from a viral infection. Onset includes a violent attack of vertigo, including nausea, vomiting, and the inability to stand or walk. Symptoms subside in several days, although feelings of unsteadiness may continue for a week or more. A swelling of the vestibular nerve following a viral infection causes vestibular neuronitis.

Sometimes the inflammation can recur over several years. A viral infection affecting the inner ear, but not the vestibular nerve, is called viral labyrinthitis. Labyrinthitis can cause hearing loss, but all other symptoms are similar to vestibular neuronitis.

Severe bacterial infections can also cause inflammation of the inner ear. These cases include risk of deafness, inflammation of the brain, and meningitis (inflammation of the membranes surrounding the brain and spinal cord). Otitis occurs when fluid accumulates in the middle ear, causing feelings of imbalance, mild turning, or vertigo. When the infection reaches the inner ear, the disease is called acute suppurative labyrinthitis. Treatment for any bacterial infection in the ear is critical to prevent long-term damage to hearing and balance organs.

PERILYMPH FISTULA Perilymph fistulas are openings that occur between the middle ear and the inner ear. This allows a hole through which perilymph can flow, changing the pressure of perilymph flowing into the brain and causing dizziness. Fistulas often form as a result of head trauma or abrupt changes in pressure. Symptoms may also include hearing loss, ringing in the ears, coordination problems, nystagmus, and headaches. Most fistulas heal with time; however, in severe cases, surgical procedures are used to close the hole, using a tissue graft.

MÈNIÉRE’S DISEASE In 1861, French physician Prosper Mèniére described Mèniére’s disease as having four particular symptoms: vertigo lasting for an hour or more, but less than 24 hours; ringing or buzzing sounds in the ear; feeling of pressure or fullness in the ear; and some hearing loss. Some people are affected in both ears; others just one ear. Onset of Mèniére’s may be related to stress, although not in all cases. Nystagmus is usually associated with the attacks.

Mèniére’s disease is thought to be caused by an accumulation of endolymph within the canals of the inner ear, a condition called endolymphatic hydrops. This causes produces a swelling in the canals containing endolymph, which puts pressure on the parts of the canals containing perilymph. The result affects both hearing and balance. In severe cases, it is feared that the endolymphatic compartments may burst, disrupting both the chemical and pressure balances between the two fluids.

The cause of the accumulation of endolymph is unknown, although it can be related to trauma to the head, infection, degeneration of the inner ear, or some other regulatory mechanism. Syphilis is often associated with Mèniére’s disease, as are allergies and leukemia. Some suggest that Mèniére’s disease is an autoimmune dysfunction. There may be a genetic predisposition to Mèniére’s disease.

Mèniére’s disease is usually treated with meclizine (Antivert), antihistamines, and sedatives. Diuretics can be used to rid the body of excess endolymph. Salt-free diets can also help to prevent the accumulation of fluid in the ears.
Systemic disorders

Dizziness may be a symptom of a disorder that affects the whole body, or systems within the body. Dizziness may also be the result of systemic toxicity to substances such as medications and drugs.

POSTURAL HYPOTENSION The major symptom of postural hypotension, also called orthostasis, is low blood pressure. When a person stands up from a prone position, blood vessels in the legs and feet must constrict to force blood to the brain. When blood pressure is low, the blood vessels do not constrict quickly or with enough pressure and the result is a lag before blood reaches the brain, causing dizziness. Postural hypotension can be treated with an increase in fluid intake or with blood pressure medication.

HEART CONDITIONS A variety of heart conditions can cause feelings of dizziness. In particular, arrhythmia, a dysfunction of the heart characterized by an irregular heartbeat, decreases blood supply to the brain in such a way as to cause balance problems. In most cases, symptoms of dizziness associated with arrhythmia result from problems with heart valves, such as narrowing of the aorta and mitral valve prolapse.

INFECTIOUS DISEASES Influenza and flu-like diseases can cause dizziness, especially if accompanied by fever. The virus herpes zoster oticus causes painful blisters and shingles . If the virus attacks the facial nerve, it may result in vertigo. Several bacterial diseases can result in dizziness, including tuberculosis, syphilis, meningitis, or encephalitis. One of the major symptoms of Lyme disease , which is caused by infection of a microorganism resulting from a deer tick bite, is dizziness.

BLOOD DISORDERS A variety of diseases of the blood result in feelings of dizziness. These diseases include anemia, or a depletion of iron in the blood, sickle-cell anemia, leukemia, and polycythemia.

DRUGS AND OTHER SUBSTANCES A variety of substances ingested systemically to prevent disorders of diseases can result in feelings of dizziness. In particular, overdose of aspirin and other anti-inflammatory drugs can cause problems with balance. Antibiotics taken for extended periods of time are also known to cause dizziness. Streptomycin is known to damage the vestibular system, if taken in large doses. Medicines that are used to treat high blood pressure can lower blood pressure so much as to cause feelings of light-headedness. Quinine, which is taken to treat malaria, can cause dizziness, as can antihistamines used to prevent allergy attacks. Chemotherapy drugs are well known to have various side effects, including dizziness. Alcohol, caffeine, and nicotine are also known to cause dizziness, when taken in large doses.

Because maintaining posture integrates so many different parts of the body, diagnosing the actual problem responsible for dizziness often requires a battery of tests. The cardiovascular system, the neurological system, and the vestibular system are all examined.

Blood pressure is one of the most important cardiovascular measurements made to determine the cause of imbalance. Usually the physician will measure blood pressure and heart rate with the patient lying down, and then again after the patient stands up. If blood pressure drops significantly and the heart rate increases more than five beats per minute, this signals the existence of postural hypotension. Dizziness in people suffering from diabetes or on blood pressure medicine may be caused by postural hypotension.
Neurological tests

Because the central nervous system is integral to maintaining balance, neurological tests are often performed on patients with symptoms of dizziness. A test of mental status is often performed to ascertain that mental function is healthy. Physicians may test tendon reflexes to determine the status of peripheral and motor nerves, as well as spinal cord function. Nerves in different parts of the body may also be evaluated. In addition, physicians may test muscle strength and tone, coordination, and gait.

Neurologists may also perform a variety of computerized scans that determine if tumors or acoustic neuromas are present. These tests include magnetic resonance imaging (MRI) , computerized tomography (CT ), and electroencephalogram (EEG).
Tests of the vestibular system

Most often performed by a otolaryngologist, the battery of tests performed to determine the health of the vestibular system include the Dix-Halpike test, electrostagmography, hearing tests, rotation tests, and posturography.

DIX-HALPIKE TEST The Dix-Halpike test, also called the Halpike test, is performed to determine if a patient suffers from benign paroxysmal positional vertigo (BPPV). The patient is seated and positioned so that his or her head hangs off the edge of the table when lying down. The patient’s head is moved 45 degrees in one direction. The patient is then asked to lie down, without moving his or her head. The same procedure will be repeated on the other side. If feelings of vertigo result from this movement, BPPV is usually diagnosed.

ELECTRONYSTAGMOGRAPHY (ENG) Considered one of the most telling diagnostic tests to determine the cause of dizziness, electronystagmography consists of a series of evaluations that test the interactions between the vestibular organs and the eyes, also called the vestibulo-ocular reflex. Results from this test can inform the physician whether problems are caused by the vestibular system or by the central nervous system.

The most common diagnostic feature observed during ENG is nystagmus, an involuntary movement of the pupils that allows a person to maintain balance. In healthy persons, nystagmus consists of a slow movement in one direction in response to a change in the visual field and quick corrective movement in the other direction. In persons with disorders of the vestibular organs, nystagmus will produce quick movements in the horizontal direction. People with neurologic disorders will show signs of nystagmus in the vertical direction or even in a circular pattern.

In most of the ENG tests, electrodes taped to the patient’s head record nystagmus as the patient is exposed to a variety of moving lights or patterns of stripes that stimulate the vestibular system. The patient may be asked to stand and lie in various positions for the tests. Also, included in the ENG is a caloric test in which warm water and cool water are circulated through the outer ear. This causes a slight expansion or contraction of the endolymph in the inner ear and simulates movement cues to the brain.

HEARING TESTS Because the cochlea and the vestibular organs are adjacent to one another, hearing dysfunction can often be related to problems with dizziness. Audiograms include tests for both hearing and interpreting sounds, and can determine whether or not problems exist in the middle ear, the inner ear, or the auditory nerve.

ROTATION TESTS Rotation tests evaluate the vestibulo-ocular reflex and provide important information when the dysfunction is common to both ears. Electrodes are usually taped to the face to monitor eye movement, and the patient is placed in a chair. The chair rotates at different speeds through different arcs of a circle. The audiologist may also ask the patient to focus on different objects as the chair is rotated.

POSTUROGRAPHY During posturography tests, a patient stands on a platform that measures how weight is distributed. During the test, the patient will close and open his or her eyes or look into a box with different visual stimuli. The platform is computer controlled so that it can gently tip forward or backward or from side to side. Posturography measures how much the patient sways or moves in response to the stimuli. This provides information on the function of the proprioceptive system, as well as the vestibular system.

If symptoms of dizziness are found to be associated with systemic diseases such as diabetes, hypotension, or other infectious diseases, or with neurological disorders, treatment for the dizziness is usually successful.

In many patients, dizziness caused by vestibular dysfunction tends to dissipate with time and with little treatment. However, available and common treatments for vestibular problems include physical therapies, medications, and surgeries. In addition, low-salt diets, relaxation techniques, and psychological counseling may be used as treatment.
Exercises and therapy

The physical therapies to decrease dizziness fall into two major groups. Compensation therapies help train the patient’s brain to rely on the sensory information it receives to maintain balance, and to ignore information from damaged organs. Exercises in a compensation program are designed to focus on the movements that cause dizziness so that the brain can adapt to these behaviors. In addition, exercises that teach the patient how to keep the eye movements separate from head movements and to practice balancing in various positions are used.

Specific exercises aimed at relieving benign paroxysmal positional vertigo (BPPV), called canalith repositioning procedures, have recently been developed. By turning the head to one side and moving from a sitting to lying position in a certain sequence, BPPV can be quickly relieved. The movements in the canalith repositioning procedures are intended to move calcium carbonate crystals from the semicircular canals back to the utricle. The success rate with these exercises can be up to 90%.

A variety of medications are used to treat vertigo. These include vestibular suppressants, which seem to work by decreasing the rate of firing of nerve cells. Common vestibular suppressants are meclizine (Antivert, Bonine, and Vetrol). Also prescribed are anti-nausea medications such as promethazane (Phenergan) and anti-histamines (Benadryl, Dramamine). For dizziness brought on by anxiety attacks, anti-anxiety drugs such as diazepam (Valium) and lorazepam (Ativan) may be used. These drugs all have side effects and are seldom prescribed for long periods of time.

Surgery is usually the last step in the treatment of dizziness, only used after therapy and medications have failed. One of the more common surgical procedures for treating vestibular disorders is patching perilymph fistulas, or tears, at the tops of the semicircular canals. Surgery may also be used to drain excess fluid from the endolymphatic canals to relieve endolymphatic hydrops. Cutting the vestibular nerve just before it joins with the auditory nerve to form the eighth cranial nerve can also be performed to alleviate severe problems with dizziness. Finally, the entire labyrinth can be destroyed in a procedure called a labyrinthectomy, although this is usually only performed when hearing has been completely lost as well.

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Vestibular Disorders Association. P.O. Box 4467, Portland, OR 97208. (503) 229-7705 or (800) 837-8428. .

Juli M. Berwald, PhD

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