Biology 202
2001 Third Web Report
On Serendip

This is the everyday reality for a chronically dizzy person. Following headaches and lower-back pain, dizziness is the third most common medical complaint in the United States. More than 90 million people in the United States will experience a spell of dizziness at some point in their lives (1).

Dizziness is a sensation people feel when they lose their sense of spatial orientation. In other words, people feel dizzy when they lose some of their immediate contact with their physical surroundings. A simple disoriented feeling may occur, or one may experience a feeling of movement or of being off balance (2). In most cases, dizziness arises naturally from unusual changes that disrupt the normal feeling of stability. However, a disturbance or a disease in the system that maintains balance can also cause dizziness (3). What could be the cause of this internal lack of balance? Although many forms of dizziness exist, such as Meniere's disease, I am going to focus on what keeps us balanced.

The issue of balance first interested me when my mother had gone to see an acupuncturist concerning her high blood pressure. Not only did she come in hopes of finding a cure for her high blood pressure, she also found that she suffers from balance problems. The Chinese guru of an acupuncturist said, "Your whole body is out of balance. Fire blazes within you without equilibrium. You should take a vacation." Apparently, correlation exists between blood pressure and physical balance. Immediately, I became worried and confused. I have been searching for the cause of my mother's problems for some time now. Why is it that she never even noticed that the world was out of balance in her perspective? She always subtly mentioned the feeling of dizziness and the constant coldness of her right shoulder. But I never realized how serious her situation was. I now know that these symptoms are due to an imbalance. For instance, I was horrified to find out that the constant coldness of my mother's right shoulder comes from the non-circulation of blood to that part of her body.

When I least expected to find answers, my questions began to unravel during my externship with an otolaryngologist. One day in his office, the otolaryngologist asked one of his lady patients in the usual routine to follow his finger with her eyes moving from left to right. The doctor checked for rapid eye oscillations, which are often seen in dizzy people. Then the doctor asked the patient to stand up abruptly and report of any feelings of lightheadedness. "No," said the patient. Finally the otolaryngologist observed the patient walk in a straight line with her eyes closed. To my surprise, she did not succeed. How can this be? The doctor explained that the balance problem originates from an imbalance in the inner ear.

Although we use the balance system every time we move from one position to another, most people take the balance system for granted. When we are healthy, we hardly ever think twice about walking on the beach or passing from the sidewalk onto the grass. In addition to body movements, the balance mechanism helps us control our eye movements. Not until our balance system goes haywire do we realize how much we rely on this system (4).

A person's sense of balance is maintained by a complex interaction of the visual inputs, the proprioceptive sensors (the gravity and stretch sensors found in muscles, skin, and joints), the inner ear vestibular system (the balance portion), and the central nervous system (brain and spinal cord). Disturbances occurring in any part of the balance system, or even within the brain's integration of inputs, can cause the feeling of dizziness or unsteadiness (5).

The sense of balance is connected to the sense of hearing in one complete system. The hearing mechanism is divided into three main parts, the outer, middle and inner ear. However, the balance system is located in the vestibular system of the inner ear portion of the hearing mechanism. The spiral shaped cochlea is the organ of hearing. Above the cochlea are three loops called the semicircular canals (6). The three semicircular canals extend favorably from the vestibule at right angles to each other. This orientation of the three canals allows the sensory organs to record movements of the head in each of the three planes of space-up or down, forward or backward, and left or right. In addition, the canals can detect changes such as speed, direction, and degree of movement (3).

In the semicircular canals and vestibule is a fluid, called endolymph, and hair cells. Endolymph and hair cells move in response to head movement and position in order to regulate equilibrium and balance (3) (7). Hair cells within the vestibule have nerve endings that detect static pressures to sense changes in the position of the head in relation to gravity (8). Crystals of calcium carbonate, called otoliths or popularly known as ear sand, lie over the hair cells in the vestibule. When the head tilts, the otoliths shift, and the hairs beneath respond to the changes in pressure. Problems can occur when these tiny crystal particles break free from their proper place and float into areas of the inner ear where they do not belong (7) and brush up against the wrong sensors at the wrong time (9).

Rotating the body in a circle several times quickly causes an inertial lag of endolymph in the semicircular canals stimulating the sensory hairs. After stopping the body rotation, one experiences dizziness because of the continued stimulation of the hair cells. The signals of the nerve endings of the hair cells deliver mixed messages as nerve impulses are sent to the brain. Similar symptoms can occur when flushing hot and cold water into the outer opening of the ear. By changing the temperature, the endolymph of the semicircular canals produce currents that change the perception of balance. Researchers have conducted many clinical tests using temperature and even electrical currents to stimulate the nerve endings of the two sacs of the vestibule (8).

Whenever we move, the brain receives sensory information from the balance system of the inner ear, as well as information from the eyes, joints, and muscles. The brain interprets the information and sends signals to the muscles to correct positioning of the arms, legs, feet, eyes, and other parts of the body to maintain balance (6). Without proper communication of sensory information, disturbance of the balance system can occur and cause the experience of dizziness.

Dizziness can occur when any one part of the balance system is disturbed. For example, when someone reads while riding in a car, the inner ear senses the movement of the vehicle. However, the eyes gaze steadily at a nonmoving book causing imbalance. The different parts of the balance system do not agree. Normally, the brain relies on signals from the eyes, muscles, and the inner ear to maintain balance. The eyes, because they are staring at a book, tell the brain that the environment is motionless. Although the muscles tell the brain that the reader is sitting in a car, the reader's head may move from side to side as the car moves. Thus, the inertia of the endolymph in the inner ear tells the brain that movement is occurring. When the brain has to choose, the brain believes the ears over the eyes leading to a conflict. The resulting sensory conflict may lead to the typical symptoms of motion sickness: dizziness, nausea, vomiting, and sweating (3).

In class, we have discussed sleep to a great extent. Maybe the imbalance in the inner ear explains why we experience the strange sensation of feeling off balance while trying to fall asleep. This is only a hypothesis.

Imbalance also occurs from heart trouble. Disorders of blood circulation are among the most common causes of dizziness. When our brains do not receive enough blood flow, we feel lightheaded. Almost everyone has experienced this when standing up quickly from a lying down position. Some people who have lightheadedness from poor circulation have more serious problems. Arteriosclerosis (hardening of the arteries) can be the cause, which is commonly seen in patients with high blood pressure, diabetes, or high levels of blood fats (cholesterol) (10).

Certain drugs, such as stimulants like nicotine and caffeine, decrease blood flow to the brain. Other factors that lead to poor circulation is salt in the diet and spasms in the arteries caused by emotional stress, anxiety, and tension. Because the inner ear is extremely sensitive to small changes of blood flow, poor blood circulation causes sensation of dizziness and imbalance (10).

Usually chronic dizziness occurs when the inner ear becomes damaged from infections or antibiotics, inner-ear disorders and, less frequently, from strokes and brain tumors. However, up to 20 percent of the causes remains a mystery because of the mixed feelings and messages that individual people experience from dizziness. If ten people are asked to describe exactly how dizziness feels to them, ten different answers will be given. This is because dizziness is not merely a physical sensation. Dizziness can become correlated with panic and make situations more complicated

Chronically dizzy people tend to suffer from anxiety and depression. Researchers have found direct connections between the locus coeruleius (a cluster of neurons in the brain stem that cause arousal, fear, and anger) and the vestibular nuclei (which process inner ear signals to the brain stem). These centers send nerve fibers commonly to the parabrachial nucleus, which can communicate with neural pathways and cause anxiety. In earlier studies, a high concentration of norepinephrine (the flight-or-fight hormone) was found in areas of the brain that manage the adjustment of one's posture (1).

Furthermore, recent research suggests that serotonin mediates at least three pathways into vestibular nuclei. This might explain why chronically dizzy patients often respond to Prozac and other selective serotonin reuptake inhibitors. This is like the "chicken or the egg" dilemma. Neither chronic dizziness nor anxiety causes the other; instead each is part of the same fundamental network (1).

I have been wondering what is life may be like for people who have chronic dizzy spells? Sadly to say, the medical field has overlooked dizziness. One man living with chronic dizziness stated, "I don't dream dizzy. I like to sleep. It's an escape from this torture(11)." This suggests that the I-function is not aware of dizziness in when one sleeps. A woman with chronic dizziness quoted, "I'm surprisingly thankful that I don't remember what it's like not to have this illness (11)." The medical field should be more concerned about dizziness. Not only is it a neurological problem, but also a psychological one. Chronic dizziness is hard to assess without having experience for oneself.

Although I am relieved to find supporting evidence for my mother's balance problem, I am somewhat disheartened to understand. It makes me sad to think that my mother could be concealing her internal battle in order to appear in control. On the other hand, I am glad that I have become more aware of her situation. The next step is to cure the problem.

WWW Sources

2)Vertigo and Dizziness Explained , Courtesy of Di-Vertigo

3)Dizziness , Hope Through Research

4)Dizziness and Balance Problems , online leaflet

5) Dizziness, Vertigo, Disequilibrium & Presyncope , Physician's Hearing and Dizziness Center

6) Dizziness , presented by the Hearing Alliance of America

7)Equilibrium , Lycos Zone Research Center website

8) Dizziness , Britannica website

9) Treating Dizziness is a Delicate Balancing Act , the Detroit News website

10) What can you do for Dizziness and Motion Sickness , About Ears website

11)Living with Dizziness , Vestibular Disorders Hotsheet website

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