Benign Paroxysmal Positional Vertigo (BPPV):
BPPV is a disease of the inner ear's gravity perception mechanism. Within the semicircular canals (inner ear tubes) are small crystals composed of calcium carbonate; the same substance contained in oyster shells. Normally, the crystals rest on a membrane that allows the brain to perceive the position of the head relative to gravity. These crystals can become dislodged and float around in the semicircular canals. This causes an aberration in the brain's perception of gravity, which induces the sensation of spinning or vertigo. This vertigo always is associated with moving the head in certain positions, such as looking up, turning over in bed, or lying down. This vertigo typically lasts about 30 seconds, but nausea may last longer. BPPV typically is diagnosed by using video nystagmography to record characteristic eye movements during head positioning. BPPV is best treated with specialized maneuvers (canalith repositioning maneuvers), which involve turning the head so that the crystals move back into their normal position. These maneuvers are effective over 80% of the time. Very rarely, surgery may be required to alleviate positional vertigo.
Ménière's disease is relatively rare compared to other more common disorders such as vestibular neuritis and benign paroxysmal positional vertigo. This condition affects 46 out of every 100,000 people and most patients are over the age of forty. A typical Ménière's attack involves a severe spinning vertigo with imbalance as well as nausea and vomiting. Characteristically, the attacks are accompanied by fluctuations of hearing and sometimes tinnitus (ringing in the ears). Most patients with Ménière's describe fullness in one or both ears. The attacks usually last about four hours, but fatigue and nausea may persist for days. Ménière's disease is caused by abnormal accumulations of fluid in the inner ear and increases of inner ear pressure. The diagnosis often can be made with an accurate history and hearing tests alone, however, specialized tests such as electronystagmography, vestibular evoked myogenic potentials, and electrocochleography may be necessary. The treatment consists of medications, a special low salt diet, and only rarely, surgery. Vestibular rehabilitation is considered to be helpful only in cases of persistent, non-fluctuating inner ear injury.
Ototoxicity is the term used to describe damage to the ear caused by toxic substances. This occurs when individuals come into contact with drugs or chemicals that are poisonous to the inner ear or to the nerve that supplies the inner ear (vestibulocochlear nerve). Because the inner ear is involved in both hearing and balance, ototoxicity can result in problems with either or both of these senses. Symptoms vary considerably from drug to drug and person to person. They range from mild imbalance to severe vertigo, tinnitus (ringing in the ears) to total hearing loss. If symptoms involve both the right and left inner ears, the patient may not have vertigo or hearing loss, but severe imbalance and blurred vision caused by poor stabilization of the eyes. This also causes the inability to tolerate head movement. The diagnosis is based upon the patient's history, symptoms, and test results. Tests that may be used to determine how much hearing or balance function has been lost include the vestibular autorotation test (VAT), electronystagmography (ENG), computerized dynamic posturography (CDP), auditory brainstem response (ABR), and pure tone audiometry. The goal of treatment is to help the brain become accustomed to the changed information from the inner ear and to assist the individual in developing other ways to maintain balance. Greater use of vision and muscle sensory information (proprioception) can be developed through formal physical therapy and a program of general physical conditioning and exercise.
In Vestibular neuritis, dizziness is attributed to a viral infection of the vestibular nerve. In older patients, this can be secondary to ischemic damage to the inner ear or vestibular nerve. The vestibular nerve carries information from the inner ear to the brain and this allows the brain to determine the position of the head and body in space and about head movement. When one of the two vestibular nerves is affected, there is an imbalance between the two sides, and vertigo appears. If hearing loss also is associated with the dizziness, the problem is called "labyrinthitis." The symptoms of both vestibular neuritis and labyrinthitis typically include dizziness or vertigo, disequilibrium or imbalance, and nausea. At onset, the dizziness is constant and may occur without head movement. After a few days to a week, symptoms are often only precipitated by sudden head movements. For the first several days, dizziness and nausea can be treated with suppressive medications. Long-term use of medications, however, can actually impede full recovery. Vestibular rehabilitation is the definitive treatment for the symptoms associated with this vestibular neuritis.
Acoustic neuromas, also known as vestibular schwannomas, are non-malignant tumors of the eighth cranial nerve. Most commonly they arise from the covering cells (Schwann cells) of the inferior vestibular nerve. These cells provide the insulation of the nerves, much like the insulation around an electrical wire. Acoustic neuromas usually cause hearing loss, but may not cause dizziness or imbalance. Acoustic neuromas are relatively rare as only about 10 tumors are newly diagnosed each year per million persons in the United States. Diagnosis is made with MRI after changes are detected on audiometry and brain stem auditory evoked responses. Treatment options for acoustic neuromas include surgery and radiation.
Although most think of migraine as a terrible headache and nothing more, migraine is actually a complex disorder of the brain that affects 12% of all people. About 20% of people with migraine have migraine with aura. An "aura" is a symptom that can be localized to a specific brain region. Visual changes (flickering lights, dark spots, etc.) are the most common auras associated with migraine. It is well known that an aura is caused by a wave of decreased brain cell activity that spreads over the surface of the brain. A common historical misconception about migraine aura is that it is caused by "constricted blood vessels" or "decreased blood flow." This simply is not the case. Although visual changes are the most common auras, dizziness also can be a symptom caused by migraine aura if decreased brain cell activity occurs in the vestibular system. Nevertheless, the phenomenon of migraine aura does not explain all cases of dizziness in migraine patients. In fact, studies have shown that the prevalence of vertigo in migraine may be as high as 42% (Kurizky et al, 1981). Vertigo secondary to migraine can be very difficult to diagnose, especially in patients without head pain. [Yes. It is possible to suffer from migraine without having headaches!] It often is difficult to distinguish migraine-associated vertigo from Ménière's disease in these patients. It is our experience that migraine-associated dizziness is extremely common and migraine-induced dizziness is a subject of research at our center.
A perilymph fistula is a tear or defect in the oval window or round window (the thin membranes between the middle and inner ears). When a fistula is present, changes in middle ear pressure will directly affect the inner ear, stimulating the balance and/or hearing structures and causing several symptoms. These include dizziness, vertigo, imbalance, nausea, and vomiting. Some people experience ringing or fullness in the ears, and many notice a hearing loss. Most people with fistulas find that their symptoms get worse with changes in altitude (elevators, airplanes, or travel over mountains). Additionally strenuous activity or straining can trigger symptoms. Head trauma is the most common cause of perilymph fistula, however, other activities such as weight lifting or scuba diving can cause this problem. Often fistula can be diagnosed by applying pressure to the ear while measuring eye movements. Often, perilymph fistulas will heal spontaneously with rest, but sometimes surgery is required.
Transient Ischemic Attack (TIA) and Stroke:
TIAs and stroke are caused by low blood flow to the brain. When the areas of the brain that control balance (brain stem and cerebellum) suffer from low or absent blood flow, dizziness and imbalance can occur. Sometimes dizziness can occur if the vertebral arteries in the neck become narrow (vertebral stenosis). When a patient with vertebral stenosis turns his or her head in certain directions, the arteries can be pinched off and blood flow to the brain can be diminished. Dizziness or vertigo is much more often caused by inner ear problems, however, TIA and stroke are frequent causes of imbalance.
This is a very common cause of dizziness, especially in the elderly. Orthostatic hypotension is a decrease in blood pressure that occurs when an individual stands up after sitting or laying down. The drop in blood pressure is caused by pooling of blood in the legs. If blood pools in the legs, less blood is pumped by the heart to the brain and dizziness or lightheadedness occurs. Orthostatic hypotension is generally treated with hydration, elastic stockings, and sometimes with medications. The diagnosis is made by measuring the blood pressure and heart rate in the recumbent and standing positions while the patient's symptoms are documented.
An arrhythmia is an electrical conduction abnormality of the heart. An arrhythmia can lead to an irregular heartbeat that causes less blood to be pumped to the brain and this can lead to dizziness. In general, cardiac arrhythmias can be treated with medications, but sometimes a pacemaker may be required.
Infrared Video Nystagmography (VNG) and Electro-nystagmography (ENG)--Tests Mostly for Horizontal Canal Function:
Thanks to new computer technology, eye movements can be tracked precisely under several circumstances. ENG records eye movements with electrodes that are attached to the skin around the eyes. VNG records eye movements directly using infrared cameras placed in front of the eyes. Both nystagmography methods are different ways of measuring the same thing. Video nystagmography is generally more precise and is the method of choice in most modern facilities. Nystagmography records small jerking eye movements called "nystagmus." Normally, these jerking eye movements occur whenever the inner ear sends signals to the brain that signify that the body is moving relative to the visual environment (for example, while spinning in a rotating chair or while standing on a merry-go-round). Usually, nystagmus also occurs whenever the patient experiences vertigo caused by vestibular disease. During nystagmography testing, the eye movements are recorded in several different head positions in order to diagnosis positional vertigo. Positional vertigo can be caused by canalithiasis of any one of the six semicircular canals. In this regard, nystagmography can be an indirect clue for vertical semicircular canal function or dysfunction. Caloric testing, however, is a test only of horizontal canal function. During caloric testing, each ear is irrigated with warm and cool water. This stimulates the horizontal semicircular canal and induces nystagmus. The intensity of the nystagmus is measured and this reflects function of this canal. The advantage of caloric testing is that the right and left horizontal canals are isolated and therefor are tested separately. In other tests of canal function, the left and right sides are tested simultaneously and a single side cannot be isolated.
Dynamic Visual Acuity (DVA)--A Test of Horizontal, Posterior, and Superior Canal Function:
This is a computerized method of determining the level of visual blurring induced by head movement in the horizontal or vertical planes. Unlike VAT testing, dynamic visual acuity is a method of evaluating the functional, rather physiologic integrity of the vestibulo-ocular reflex. The disadvantage of DVA testing is that the left or right inner ears cannot be isolated during testing. Like the VAT, the DVA cannot distinguish between posterior and superior canal function.
Subjective Verticality--A Test of Utricular Function:
Subjective verticality is considered a test of utricular function. During this test, the patient stands in a completely darkened room. The patient is asked to adjust a dimly lighted bar so that it is positioned vertically (i.e., perpendicular to the floor). Many patients tilt the bar toward the inner ear that is involved in utricular dysfunction. This is because their eyes are rotated toward the side with the problem and these patients perceive the world as tilted to that side. Our center has developed an inexpensive apparatus to measure subjective verticality. This will be available soon for purchase from our web site.
Vestibular Evoked Myogenic Potentials (VEMPs)--A Test of Saccular and Posterior Canal (or inferior vestibular nerve) Function:
VEMPs are a study of saccular function via stimulation of the vestibulocollic pathway. During this study, electrodes are attached to the patient's neck over the sternocleidomastoid muscle and the ear on the same side is stimulated with clicking or tone sounds at a level of 95 dB. Electrical potentials from the muscle are amplified and filtered for analysis. VEMPs can be useful in the diagnosis of Ménière's disease. Additionally, the VEMP study can be useful for predicting the onset of paroxysmal positional vertigo (of the posterior canal type) after an attack of vestibular neuritis. Both the saccule and the posterior canal are innervated by the inferior vestibular nerve. In order for the VEMP to be recorded, the inferior vestibular nerve must be intact. If the VEMP is intact, then the innervation to the posterior canal is intact and BPPV caused by posterior canalithiasis can occur. An absent VEMP is a sign that the patient will not go on to have symptoms from posterior canalithiasis. In this sense, the VEMP is an indirect way to measure posterior semicircular canal function. An advantage of VEMP testing is that the right and left sides are isolated during testing.
Audiometry--A Test of Cochlear and Auditory System Function:
During audiometry, earphones are placed over the ears and the patient presses a button whenever a tone is heard. Several different frequencies and intensities of sound are tested. The presence or absence of hearing loss is important in determining the etiology of dizziness. If hearing loss on the side of vestibular dysfunction is detected, this suggests involvement of the cochlea or auditory nerve.
Auditory Brain Stem Responses (ABRs)--A Test of the Complete Auditory Pathway:
ABRs are a method of determining the integrity of the auditory portion of the eighth cranial nerve. This test is done by stimulating the ears with sound and then recording electrical potentials produced by the brain with electrodes placed on the scalp. The entire pathway for hearing from the ear to the brain can be studies with this technique. ABRs are used most commonly to screen for acoustic neuromas. They also can be used to localize lesions in the brainstem (for example in stroke and multiple sclerosis).
Oculomotor Testing--A Test of Brain Function:
During oculomotor testing, infrared video cameras are used to record eye movements with very high precision. Typically, the oculomotor evaluation involves several sub-tests: saccades, smooth pursuit tracking, gaze-evoked nystagmus, and optokinetic nystagmus. During each of the tests, the patient watches lights projected on a screen while the eye movements are recorded and analyzed by a computer. Certain abnormalities of eye movements then can be used to diagnose abnormalities in specific brain regions. Oculomotor testing is a subject of intensive research at our center.
Vestibular rehabilitation is the primary treatment for many causes of dizziness. This treatment consists of several tailored exercises that are designed with two concepts in mind: "adaptation" and "substitution." Adaptation is designed to retrain the brain to compensate for loss of inner ear function. When one inner ear is injured and not functioning properly and the other inner ear is functioning well, the brain perceives the mismatched signals as movement. This is analogous to an airplane with an engine on each wing. If one engine stops, the plane will no longer fly straight unless corrected by the pilot or an onboard computer.
Adaptation is a process by which the brain learns to balance out asymmetric signals received from the inner ears. In this sense, the brain is like the computer that makes the plane fly straight when one engine is out. Adaptation is made possible by the "programming" offered by vestibular rehabilitation exercises.
Substitution is a process by which a patient learns to compensate for the disability caused by inner ear dysfunction by relying more on other senses. Balance depends not only on inner ear function, but also on visual cues and sensory input from the extremities and trunk. The patient is taught to "substitute" inner ear input by paying more attention to their visual surroundings and other sensations.
The canalith repositioning maneuvers are specific treatments for benign paroxysmal positional vertigo (BPPV). There are several techniques that can be used to accomplish these maneuvers, however, all involve turning the head in certain positions that use the force of gravity to move dislodged calcium carbonate crystals back to their normal position. These maneuvers are extremely effective and most patients with BPPV enjoy immediate relief from vertigo.
For the majority of patients with dizziness, medications are a negative influence on recovery. This is especially true for patients suffering from chronic dizziness after an acute attack of vestibular neuritis. Recent studies have shown that medications can actually interfere with the adaptation process that occurs naturally and during vestibular rehabilitation. Nevertheless, certain medications can be very helpful for certain causes of vertigo, especially fluctuating conditions such as migraine and Ménière's disease.
Any condition that can cause dizziness also can cause imbalance. There are, however, a few conditions that primarily cause imbalance, but do not usually cause dizziness or vertigo.
Parkinson's disease (PD) often causes severe imbalance. This typically occurs because patients with this disease have postural reflex abnormalities. Normally when the body sways in one direction, a reflex occurs that causes muscles to contract and the body sways in the opposite direction in order to prevent a fall. Patients with PD have problems with this reflex and when they began to sway they often continue to sway in the same direction until they fall. PD usually is diagnosed with a thorough neurological examination. Oculomotor testing also can be useful in making the diagnosis.
Peripheral neuropathy is a disease that affects the small nerve endings throughout the body. Usually the small nerves in the feet and toes are the first to be affected and this causes numbness in the feet. Patients with peripheral neuropathy have imbalance because they cannot feel the floor beneath their feet. This imbalance can be especially severe on unstable surfaces and when the patients attemps to walk in darkness, as visual cues are important to these patients. Peripheral neuropathy can be diagnosed with a detailed neurological examination and nerve conduction studies.
A stroke is a scar in the brain caused by absent or decreased blood flow. Usually this occurs because of narrowing of an artery or a blood clot that goes to the brain. If a stroke happens to occur in an area of the brain that is important for balance (i.e., the cerebellum or brain stem), severe imbalance can occur. Stroke is most often diagnosed with a careful neurological examination and magnetic resonance (MRI) or computed tomography (CT) imaging.
Imbalance is very common is patients with multiple sclerosis (MS). In MS, the insulation around brain and spinal cord cells is defective. The lesion in the brain or spinal cord caused by the defective insulation is called a "plaque." If a plaque occurs in the regions of the brain responsible for balance such as the brain stem or the cerebellum, the patient may experience severe imbalance and ataxia.
This is a disease that causes shrinkage and dysfunction of an area of the brain called the cerebellum. The cerebellum is important for coordinating the movements neccesary to maintain balance. This diagnosis can be made by examination, MRI, and oculomotor testing.
Vision is very important for balance. Conditions causing poor vision such as cataracts and macular degeneration can lead to imbalance, particularly in patients who also have any of the conditions listed above.
The Neurological Examination:
A complete neurological examination is always the starting point for diagnosing balance disorders. A highly trained neurologist typically performs the examination, though other medical professionals specifically trained to evaluate patients with brain disorders may also be involved. The neurological examination is mostly science, but partly art and neurologists have been performing their examinations in pretty much the same way for more than 100 years. During the neurological examination, the patient may be asked to perform certain tasks that evaluate a specific part of the brain or spinal cord. Also, reflexes and strength are tested in different ways. In patients with balance disorders, observing the patients "gait," or manner of walking is often most important. After this initial examination, the neurologist typically has a certain diagnosis in mind and further diagnostic testing can be ordered (for example, an MRI of the brain) to confirm the suspected diagnosis.
Computerized Dynamic Posturography (CDP):
Normal balance requires the integration of proprioceptive (sensation from the feet), visual, and vestibular (inner ear) inputs. During posturography, the patient stands on a computerized platform while balance is measured under different circumstances that stress each of the three input systems. For example the floor may move beneath the patient's feet, or the visual surroundings may tilt in a certain directions. The reflex movements made by the patient to keep from falling are measured and this helps determine which part of the balance system is affected by disease.
During oculomotor testing, infrared video cameras are used to record eye movements with very high precision. Typically, the oculomotor evaluation involves several sub-tests: saccades, smooth pursuit tracking, gaze-evoked nystagmus, and optokinetic nystagmus. During each of the tests, the patient watches lights projected on a screen while the eye movements are recorded and analyzed by a computer. Certain abnormalities of eye movements then can be used to diagnose abnormalities in specific brain regions.
Magnetic Resonance Imaging (MRI):
MRI is a method of capturing high-resolution pictures of the brain. During an MRI, the patients lay in a large tube while magnetic fields are used to capture information about the brain. A powerful computer translates the information into images that are so detailed that the modern MRI has been compared to direct viewing of the brain (like that seen during autopsy). MRI can be crucial in diagnosing disorders of the brain (such as stroke) that can lead to imbalance.
The treatment of imbalance is extremely variable and depends greatly on the disorder being treated. For example, if the diagnosis is Parkinson's disease, certain medications that contain levodopa may be used for treatment. If a patient is diagnosed with multiple sclerosis, medications that affect the immune system may be used. Physical therapy exercises, especially techniques that strengthen leg muscles are helpful for nearly all causes of imbalance. At our center, medical treatment for imbalance is started together with physical therapy. The therapist is made aware of the diagnosis so that rehabilitation can be tailored to each specific case.