Dizziness is a symptom, not a disease. It may be defined as a subjective sensation of unsteadiness or imbalance, a disorientation in relation to one’s surroundings. Dizziness can be caused by many different disease and varies from a mild unsteadiness to a severe whirling sensation known as vertigo. Dizziness may or may not be accompanied by a hearing impairment.
The human balance system is made up of four parts. The brain acts as a central computer receiving information in the form of nerve impulses (messages) from its three input terminals: the eyes, the inner ear, and the muscles and joints of the body. There is a constant stream of impulses arriving at the brain from these input terminals. All three systems work independently and yet work together to keep the body in balance.
The eyes receive visual clues from light receptors that give the brain information as to the position of the body relative to its surroundings. The receptors in the muscles and joints are called proprioceptors. The most important ones are in the head and neck (head position relative to the rest of the body) and the ankles and joints (body sway relative to the ground).
The inner ear balance mechanism has two main parts: the three semicircular canals and the vestibule. Together they are called the vestibular labyrinth and are filled with fluid. When the head moves, fluid within the labyrinth moves and stimulates nerve endings that send impulses along the balance nerve to the brain. Those impulses are sent to the brain in equal amounts from both the right and left inner ear. Nerve impulses may be started by the semicircular canals when turning suddenly, or the impulses may come from the vestibule, which responds to changes of position, such as lying down, turning over or getting out of bed.
When one inner ear is not functioning correctly, the brain receives nerve impulses that are no longer equal, causing it to perceive this information as distorted or off balance. The brain sends messages to the eyes, causing them to move back and forth, making the surroundings appear to spin. It is this eye movement (called nystagmus) that creates a sensation of things spinning.
Remember to think of the brain as a computer with three input terminals feeding it constant up-to-date information from the eyes, inner ear and muscles and joints (proprioceptors). The brain itself is divided into several different parts. The most primitive area is known as the brainstem, and it is here that processing of the input from the three sensory terminals occurs. The brainstem is affected by two other parts of the brain, the cerebral cortex and the cerebellum.
The cerebral cortex is where past information and memories are stored. The cerebellum, on the other hand, provides automatic (involuntary) information from activities which have been repeated often.
The brainstem receives all these nerve impulses: sensory from the eyes, inner ear, muscles and joints; regulatory from the cerebellum; and voluntary from the cerebral cortex. The information is then processed and fed back to the muscles of the body to help maintain a sense of balance.
Because the cortex, cerebellum and brainstem can eventually become used to (ignore) abnormal or unequal impulses from the inner ear, exercise may be helpful. Exercise often helps the brain to habituate to (get used to) the dizziness problem so that it does not respond in an abnormal way, does not result in the individual feeling dizzy. An example of habituation is seen with the ice skaters that twirl around, stop suddenly, and do not apparently have any balance disturbance.
Sensations of unsteadiness, imbalance or disorientation in relationship to one’s surroundings may result from disturbances in the ear, the neck, the muscles and joints, the eyes, the nervous system connections of these structures or a combination of these.
Ear dizziness results from disturbances in the circulation or fluid pressure in the inner ear chambers or from direct pressure on the balance nerve that transmits impulses from the inner ear to the brain.
The inner ear mechanism approximates the size of a pea and is extremely sensitive. There are two inner ear chambers: one for hearing (cochlea) and one for balance (vestibule and semi-circular canals). These chambers contain a fluid that bathes the delicate nerve endings. These nerve endings are stimulated when there is movement of the fluid. Nerve impulses are then transmitted to the brainstem by the hearing and balance nerves. The nerves pass through a small bony canal (internal auditory canal) accompanied by the facial nerve.
Any disturbance in pressure, consistency or circulation of the inner ear fluids may result in acute, chronic or recurrent dizziness, with or without hearing loss and head noise. Likewise, any disturbance in the blood circulation to this area or to the nerve may result in similar symptoms.
Dizziness may also be produced by over-stimulation of the inner ear fluids such as one encounters when he/she spins very fast and then stops suddenly.
Central dizziness is an unsteadiness brought about by failure of the brainstem to coordinate or interpret correctly the nerve impulses that it receives. An example of this is the “swimming feeling” or unsteadiness that may accompany congestion or a circulation problem in the brainstem (the “computer” mentioned on page 5). This circulatory inefficiency, producing unsteadiness, with or without hearing impairment, may be due to age, metabolic or allergic dysfunction, a mild stroke, tumors or injury. This same type of problem can be due to stress, tension or depression. A feeling of pressure or fullness in the head and ears is common under these circumstances.
Neck dizziness (cervical vertigo) results from abnormal or uncoordinated nerve impulses being sent to the brain from the neck muscles.
The neck muscles are constantly sending nerve impulses to the brainstem to help maintain equilibrium. Spasm (tenseness) of the muscles may result in an abnormal nerve discharge, leading to unsteadiness or dizziness. This spasm may result from injury, from arthritis of the spine, or from pressure on nerves in the neck.
Muscle-joint dizziness is relatively uncommon. Any disturbance of sensation arising from the muscle and joints in the limbs such as occurs in the muscular dystrophies and other abnormalities produce this type of unsteadiness. Such an example is the unsteadiness experienced when one tries to walk on a leg that has “gone to sleep”.
Eye muscle imbalance or errors of refraction may produce unsteadiness. AN example of this is the unsteadiness which may result when one attempts to walk while wearing glasses belonging to another individual.
Another example of visual dizziness is that occasionally produced if one is seated in a car, looking out the side window at passing objects. The eyes respond by sending a rapid series of impulses to the brain indicating that the body is rotating. On the other hand, the ears and the muscle-joint systems send impulses to the brain indicating that the body is not rotating, only moving forward. The brainstem, receiving these confused impulses (from the eyes indicating rotation, from the ears and muscle-joint systems indicating forward motion), sends out equally confused orders to the various muscles and glands that may result in sweating, nausea and vomiting. In this situation when one sits in the front seat looking forward, the eyes, ears and muscle-joint systems work more in uniform and one is less likely to develop car sickness.
A visual disturbance may be caused by dizziness from other sources. Intermittent inability to focus the eyes, difficulty reading or intermittent blurring of vision, although at times the result of anxiety or tension, may result from small reflex movements of the eye called nystagmus. This nystagmus is common during severe dizziness.
Persons subject to dizziness should exercise caution when swimming. Buoyancy of the water results in essentially a weightless condition, and visual orientation is greatly impaired if one’s head is under water. As a result, orientation depends almost entirely on the inner ear balance canals. An attack of dizziness at this time could be very dangerous.
Similarly, individuals who have lost both inner ear balance canals should avoid underwater swimming.
Any disturbance affecting the function of the inner ear or its central connections may result in dizziness, hearing loss or tinnitus (head noise). These symptoms may occur singly or in combination, depending upon which functions of the inner ear are disturbed.
Ear dizziness may appear as a whirling or spinning sensation (vertigo),. It may last seconds, minutes or hours, and is frequently aggravated by head motion or sudden position change. Nausea and vomiting may occur but one does not lose consciousness as a result of inner ear dizziness.
Dizziness may be caused by any disturbance in the inner ear, the balance nerve or its central connections. This can be due to a disturbance in circulation, fluid pressure or metabolism, infections, neuritis, drugs, injury or tumors.
An extensive evaluation is required at times to determine the cause of dizziness. The tests necessary are determined at the time of examination, and may include detailed hearing and balance tests (electronystagmography, posturography, rotary chair), CAT scan or MRI, blood tests and metabolic and allergic evaluations. A general physical examination and neurological tests may be advised.
The object of this evaluation is to be certain that there is no serious or life-threatening disease, and to pinpoint the exact site of the problem. This lays the groundwork for effective medical or surgical treatment.
Any interference with the circulation to the delicate inner ear structures or their central connections may result in dizziness, at times with hearing loss and tinnitus. These circulatory changes may be the result of blood vessel spasm, partial or total occlusion or rupture with hemorrhage.
Postural dizziness is a common form of balance disturbance due to circulatory changes. It is characterized by a sudden brief feeling of lightheadedness upon standing. It takes a few seconds for the heart to overcome the gravity change and pump blood to the brain. Arising from bed slowly usually minimizes the disturbance.
In this condition a patient experiences a sudden burst of severe whirling (vertigo) with changes of head and body position. It last briefly (5-60secs) and may be accompanied by nausea, rarely vomiting. It can occur when looking up, lying down, or rolling over in bed. However, the dizziness may not occur every time.
The course is characterized by waxing and waning of symptoms but is usually self limiting. The disorder is thought to result from dislodgement of fine calcium crystals (otoliths) from the delicate balance sense organ, the utricle. With changes of head position, the crystals tumble and result in an inner ear fluid shift causing vertigo. The cause may be from trauma, aging, infection, or unknown reasons. Treatment may consist of watchful waiting, physical therapy (canalith repositioning maneuver), sedatives, or rarely surgery.
Imbalance due to ear infection is usually abrupt and severe in onset often associate with nausea and vomiting. Such imbalance may occur with or without hearing impairment. The infection may be caused by either a virus or bacteria.
Metabolic disturbances and allergies can produce dizziness, with or without associated hearing loss, by interfering with the function of the inner ear or its central connections. Occasionally, hearing loss may occur without the presence of dizziness. The most common metabolic disturbances result from decreased thyroid function, abnormal sugar tolerance and inhalant or food allergies.
Injury to the head occasionally results in dizziness due to damage to the inner ear and brain. The unsteadiness is at times prolonged, and may or may not be associated with hearing loss and head noises.
Dizziness, with or without hearing impairment, may result from a perilymphatic fistula, a leak of inner ear fluid into the middle ear through one of the two inner ear windows. The fistula may appear spontaneously or may follow a head injury, a sudden change in atmospheric pressure (barotrauma) or ear surgery.
A non-cancerous tumor occasionally develops on the balance nerve deep in the ear bone. When this occurs, unsteadiness, hearing loss and head noise may develop. Extensive hearing tests, balance tests and brain imaging (MRI) are necessary to diagnose such tumors.
Meniere’s Disease is a common cause of repeated attacks of dizziness. It is due to increased pressure of the inner ear fluids.
Fluids in the inner ear chambers are constantly being produced and absorbed by the circulatory system. Any disturbance in this delicate relationship results in over-production or under-absorption of the fluids. This leads to increased fluid pressure (hydrops) that in turn produces dizziness which may or may not be associated with fluctuating hearing loss and tinnitus. Fortunately, this usually affects only one ear.
Meniere’s Disease is characterized by attacks of dizziness that vary in duration from a few minutes to several hours. Hearing loss and head noise usually accompany the attacks. The attacks of dizziness may occur suddenly and without warning. Violent spinning, whirling and falling, associated with nausea and vomiting, are common symptoms. A sensation of pressure and fullness in the ear is usually present.
Attacks of dizziness may recur at irregular intervals. The individual may be free of symptoms for years at a time. If the attacks do recur, they are usually less severe and of shorter duration than in the initial attack. In between attacks, the individual tends to remain free of symptoms.
Occasionally hearing impairment, head noise and ear pressure occur without dizziness. This type of Meniere’s Disease is called cochlear hydrops. Similarly, episodic dizziness and ear pressure may occur without hearing loss and tinnitus: this is called vestibular hydrops. Treatment of both of these is the same as for Meniere’s Disease.
Treatment of Meniere’s Disease may be medical or surgical. It is aimed at improving the inner ear circulation and controlling the fluid pressure changes of the inner ear chambers. Surgery is indicated when medical treatment fails to relieve the acute attacks of dizziness. The type of operation selected depends upon the degree of hearing impairment in the affected ear since every effort is made to preserve this hearing. In some cases, the hearing may be improved following surgery and in others it may become worse; usually it remains the same. Head noise may or may not be relieved and in some cases may even become more marked. Surgery is successful in relieving acute attacks of dizziness in the majority of patients.
There are many causes of dizziness. This dizziness may or may not be associated with a hearing loss. In most instances, the distressing symptoms of dizziness can be greatly benefited or eliminated by medical or surgical management.