What is a balance disorder?
Figure 1: The vestibular system in relation to the ear. Credit NIH Medical Arts.
A balance disorder is a condition that makes you feel unsteady or dizzy, as if you are moving, spinning, or floating, even though you are standing still or lying down. Balance disorders can be caused by certain health conditions, medications, or a problem in the inner ear or the brain.
Our sense of balance is primarily controlled by a maze-like structure in our inner ear called the labyrinth, which is made of bone and soft tissue. At one end of the labyrinth is an intricate system of loops and pouches called the semicircular canals and the otolithic organs, which help us maintain our balance. At the other end is a snail-shaped organ called the cochlea, which enables us to hear. The medical term for all of the parts of the inner ear involved with balance is the vestibular system (see Figure 1).
How does the vestibular system work?
Figure 2: The role of the cupula in balance Credit: NASA
Our vestibular system works with other sensorimotor systems in the body, such as our visual system (eyes) and skeletal system (bones and joints), to check and maintain the position of our body at rest or in motion. It also helps us maintain a steady focus on objects even though the position of our body changes. The vestibular system does this by detecting mechanical forces, including gravity, that act upon our vestibular organs when we move. Two sections of the labyrinth help us accomplish these tasks: the semicircular canals and the otolithic organs.
The semicircular canals are three fluid-filled loops arranged roughly at right angles to each other. They tell the brain when our head moves in a rotating or circular way, such as when we nod our head up and down or look from right to left.
Each semicircular canal has a plump base, which contains a raindrop-shaped structure filled with a gel-like substance (see Figure 2). This structure, called the cupula, sits on top of a cluster of sensory cells, called hair cells. The hair cells have long threadlike extensions, called stereocilia, that extend into the gel. When the head moves, fluid inside the semicircular canal moves. This motion causes the cupula to bend and the stereocilia within it to tilt to one side. The tilting action creates a signal that travels to the brain to tell it the movement and position of your head.
Between the semicircular canals and the cochlea lie the otolithic organs, which are two fluid-filled pouches called the utricle and the saccule. These organs tell the brain when our body is moving in a straight line, such as when we stand up or ride in a car or on a bike. They also tell the brain the position of our head with respect to gravity, such as whether we are sitting up, leaning back, or lying down.
Like the semicircular canals, the utricle and the saccule have sensory hair cells. These hair cells line the bottom of each pouch, and their stereocilia extend into an overlying gel-like layer. On top of the gel are tiny grains made of calcium carbonate called otoconia. When you tilt your head, gravity pulls on the grains, which then move the stereocilia. As with the semicircular canals, this movement creates a signal that tells the brain the head’s position.
Our visual system works with our vestibular system to keep objects from blurring when our head moves and to keep us aware of our position when we walk or when we ride in a vehicle. Sensory receptors in our joints and muscles also help us maintain our balance when we stand still or walk. The brain receives, interprets, and processes the information from these systems to control our balance.
What are the symptoms of a balance disorder?
If your balance is impaired, you may feel as if the room is spinning. You may stagger when you try to walk or teeter or fall when you try to stand up. Some of the symptoms you might experience are:
- Dizziness or vertigo (a spinning sensation)
- Falling or feeling as if you are going to fall
- Lightheadedness, faintness, or a floating sensation
- Blurred vision
- Confusion or disorientation
Other symptoms are nausea and vomiting, diarrhea, changes in heart rate and blood pressure, and fear, anxiety, or panic. Some people also feel tired, depressed, or unable to concentrate. Symptoms may come and go over short time periods or last for longer periods of time.
What causes a balance disorder?
A balance disorder may be caused by viral or bacterial infections in the ear, a head injury, or blood circulation disorders that affect the inner ear or brain. Many people experience problems with their sense of balance as they get older. Balance problems and dizziness also can result from taking certain medications.
In addition, problems in the visual and skeletal systems and the nervous and circulatory systems can be the source of some posture and balance problems. A circulatory system disorder, such as low blood pressure, can lead to a feeling of dizziness when we suddenly stand up. Problems in the skeletal or visual systems, such as arthritis or eye muscle imbalance, also may cause balance problems. However, many balance disorders can begin all of a sudden and with no obvious cause.
What are some types of balance disorders?
- Benign paroxysmal positional vertigo (BPPV) or positional vertigo is a brief, intense episode of vertigo that occurs because of a specific change in the position of the head. If you have BPPV, you might feel as if you’re spinning when you look for an object on a high or low shelf or turn your head to look over your shoulder (such as when you back up your car). You also may experience BPPV when you roll over in bed. BPPV is caused when otoconia tumble from the utricle into one of the semicircular canals and weigh on the cupula. The cupula can’t tilt properly and sends conflicting messages to the brain about the position of the head, causing vertigo. BPPV sometimes may result from a head injury or just from getting older.
- Labyrinthitis is an infection or inflammation of the inner ear that causes dizziness and loss of balance. It frequently is associated with an upper respiratory infection such as the flu.
- Ménière’s disease is associated with a change in fluid volume within parts of the labyrinth. Ménière’s disease causes episodes of vertigo, irregular hearing loss, tinnitus (a ringing or buzzing in the ear), and a feeling of fullness in the ear. The cause of this disease is unknown.
- Vestibular neuronitis is an inflammation of the vestibular nerve and may be caused by a virus. Its primary symptom is vertigo.
- Perilymph fistula is a leakage of inner ear fluid into the middle ear. It can occur after a head injury, drastic changes in atmospheric pressure (such as when scuba diving), physical exertion, ear surgery, or chronic ear infections. Its most notable symptom, besides dizziness and nausea, is unsteadiness when walking or standing that increases with activity and decreases with rest. Some babies may be born with perilymph fistula, usually in association with hearing loss that is present at birth.
- Mal de debarquement syndrome (MdDS) is a balance disorder in which you feel as if you’re continuously rocking or bobbing. It generally happens after an ocean cruise or other sea travel. Usually, the symptoms will go away in a matter of hours or days after you reach land. However, severe cases can last months or even years.
How do I know if I have a balance disorder?
Everyone has a dizzy spell now and then, but the term “dizziness” may mean something different to different people. For some people, dizziness might be a fleeting sensation of spinning, while for others it’s intense and lasts a long time. Experts believe that more than four out of 10 Americans will experience an episode of dizziness significant enough to send them to a doctor.
To help you decide whether or not you should seek medical help for a dizzy spell, ask yourself the following questions. If you answer “yes” to any of these questions, talk to your doctor.
- Do I feel unsteady?
- Do I feel as if the room is spinning around me?
- Do I feel as if I’m moving when I know I’m sitting or standing still?
- Do I lose my balance and fall?
- Do I feel as if I’m falling?
- Do I feel “lightheaded” or as if I might faint?
- Do I have blurred vision?
- Do I ever feel disoriented, such as losing my sense of time or where I am?
What research is being done for balance disorders?
BPPV is the most common balance disorder. Because the source of the problem—displaced otoconia—is located deep within the ear, doctors have had to rely mainly on observation and a medical history to make a diagnosis. Researchers supported by the National Institute on Deafness and Other Communication Disorders (NIDCD) now have created a head-mounted apparatus that uses 3-D animation to map the location of otoconia in the inner ear.
The apparatus is built around a pair of infrared video goggles that gather data from eye and head movements and then sends it to a computer program for mapping. A second computer program uses the data to develop a step-by-step guide for repositioning maneuvers to dislodge the otoconia from the semicircular canals. If shown to be effective in clinical trials, the apparatus and its software programs will help doctors more accurately diagnose BPPV and guide repositioning maneuvers to ensure the best possible treatment.
Other NIDCD-supported scientists are looking at the molecular mechanisms that regulate the development of the inner ear. One research team has identified a gene that encodes a protein that helps in the formation of the semicircular canals and their related sensory tissue. Another team has identified a family of genes, called the otopetrins, which help form otoconia in mice. Findings from the mouse study could help researchers determine if otoconia destroyed by aging, medications, infections, or trauma can someday be regenerated in humans with balance problems.
NIDCD-supported scientists also are experimenting with several types of vestibular prostheses, or replacement parts, in balance-impaired animals. Researchers hope these devices will one day be used to compensate for vestibular system loss in people.
One prosthesis uses a head-mounted motion sensor to mimic the ear and brain’s natural signaling system. The sensor measures the head’s rotation and sends the information to a microprocessor. The microprocessor then converts the signals into electrical impulses and sends them to an electrode implanted in the ear. The electrode stimulates the vestibular nerve, creating a signal that helps the brain move the eyes to compensate for the head’s rotation.
A second prosthesis is designed to simulate the movement of fluid within the semicircular canal. In a normal ear, fluid changes help the brain understand the movement and position of the head. The device combines microcontroller circuitry with a tiny mechanical device that increases normal fluid movement to provide a stronger vestibular signal to the brain.
Researchers also are studying the effectiveness of different types of rehabilitative exercises as a treatment option for balance disorders. In one NIDCD-funded study, researchers have used virtual reality technology to simulate the aisles of a grocery store. Using a real cart attached to a custom-built treadmill in front of a projection screen, patients “walk” down aisles, scanning virtual store shelves for items on their list. Researchers are testing whether practicing in the virtual store will lessen episodes of dizziness in the real world, especially in visually complex environments.