Terms
- Vertigo is a word used to describe the surroundings that sometimes feel as if they are spinning.
- Imbalance refers to the sensation that one must touch or hold onto something in order to stand straight.
- Dizziness is a word used to describe a variety of feelings and sensations. It usually refers to the illusion of motion, lightheadedness, weakness, loss of balance, faintness, wooziness, and unsteadiness. Dizziness may occur for a number of reasons. It is the third most common reason people over age 65 visit their doctor, but one which rarely signals a life-threatening situation.
Balance System
The system of balance is a complex one. An important part is the vestibular labyrinth, which, along with the cochlea, is contained in the inner ear. This explains why some disorders of the inner ear produce both hearing loss and dizziness.
The vestibular labyrinth is located just above the cochlea. It consists of three loop-shaped, fluid-filled structures called semicircular canals. At the base of each semicircular canal is a sensory structure called the ampulla.
These structures keep the brain informed of the turning motions of the head. This in turn causes the eyes to move in the opposite direction of the head, keeping the image seen focused on the retina. The brain relies mainly on the vestibular labyrinth for the sense of balance, especially when information from the eyes is missing.
The three semicircular canals are connected to the vestibule. Within the vestibule are two chambers called the utricle and saccule.
The utricle is the upper chamber connecting all three semicircular canals. The saccule is the lower chamber lying closer to the cochlea. These chambers help monitor the position of the head in relation to gravity and to such linear motion as going up and down in an elevator. Each chamber contains a patch of sensory hair cells embedded in a gel-like substance. These patches contain tiny particles called otoconia.
When you bend down, the otoconia in the saccule – responsible for the detection of vertical movement – are pulled down by gravity.
When you walk forward, the otoconia in the utricle – responsible for detection of horizontal movement – lag behind.
In both these actions, the otoconia pull the gel-like substance with them. This in turn bends the embedded hair cells, causing them to send impulses along their nerve pathways to the brain about the vertical and horizontal movements.
The brain responds to these impulses, regardless of what a person is doing, by coordinating the eye movement with the head movement so that the vision remains clear. The brain also signals the skeletal muscles to react quickly to help maintain balance.
The system of balance allows a person to remain upright whether sitting, standing, or moving around. It also keeps the vision clear when the head is moving and keeps one aware of where the head is in relation to the ground.
To maintain the sense of balance, the brain must coordinate sensory information coming from the eyes, musculoskeletal nerves, and the inner ear. Then the brain sends signals to muscles throughout the skeleton on how to react and maintain a position.
Vision is very important in helping to maintain a sense of balance. When light hits the photosensitive cells at the back of the eyeball, it triggers chemical reactions that generate electrical impulses which are then communicated to the brain through the optic nerve. The brain interprets these signals as images and uses them to calculate, for example, distance and speed while walking.
The nervous system is made up of millions of nerve cells (neurons) found in the skin, muscles, and joints. When touch, pressure, and movement stimulate these cells, they send electrical impulses to the brain about what the body is doing.
Information about the movement of the neck and ankles is particularly important because it tells the brain which way the head is turned and how steady a person is on the ground.
Causes
In order for balance to be maintained, at least two of the three sensory systems must be working well.
Sudden movements can cause a feeling of dizziness. This happens because the gel-like fluid in the semicircular canals takes a while to catch up with the motion. When movement is stopped, the fluid keeps going, causing the feeling of dizziness.
Dizziness caused by environmental changes is not serious; but, sudden, severe attacks of prolonged episodes of dizziness, faintness, lightheadedness, or vertigo can be symptoms of underlying disorder or illness. While many may be caused by a disturbance of the vestibular system, other causes include:
- low blood pressure
- poor circulation (often caused by blocked arteries or heart disease)
- multiple sensory deficits (examples include diminished input from the eyes, nerves, muscles, and joints)
- anxiety disorders
- hyperventilation or rapid breathing
- disorders of the central nervous system, including multiple sclerosis and tumors
Some specific disorders
Benign Paroxysmal Positional Vertigo (BPPV)
BPPV is a common cause of vertigo and more likely to occur in those over the age of 50. It is characterized by sudden, short bursts of vertigo, usually lasting less than a minute, and typically occurring with changes in head position. Usually, there is a feeling of spinning or floating when lying on one side or with the head tipped back. The eyes move back and forth involuntarily (nystagmus) when this is happening. There may also be some nausea and a lingering fatigue and queasiness. This disturbance may come and go unpredictably for weeks or even years.
Although the exact cause is unknown, BPPV is thought to be age-related because of the gradual degeneration of the vestibular system. Sometimes, however, a blow to the head precedes the condition. Whether by aging or trauma, scientists have noticed that the tiny otoconia that normally reside in the utricle of the vestibular labyrinth break loose and accumulate in one of the semicircular canals. Certain movements may cause the particles to push in on the fluid of the inner ear, bending hair cells, and setting off brief episodes of whirling or spinning sensations.
In some cases, a simple procedure, called the canalith repositioning procedure, may correct BPPV. This procedure involves simple maneuvers for positioning the head. The goal is to move the misplaced otoconia back to the utricle progressively. It may be necessary to repeat the procedure several times before the feeling of vertigo is eliminated. Afterwards, the head must be kept upright for the next 48 hours, including during sleep. This helps ensure that the particles stay in the utricle. The success rate when using these maneuvers can be as high as 90%.
Canalith Repositioning Procedure
Each step is held for about 30 seconds.
- Move from a sitting to a reclining position, allowing the head to extend and drop over the end of the table at a 45 degree angle.
- Turn the head to the right.
- Roll over onto the right side keeping the head slightly angled while looking down at the floor.
- Return carefully to a sitting position.
- Tilt the chin down.
- Repeat, changing direction for the other ear.
Labyrinthitis
This is an inflammation of the inner ear (labyrinth) that can affect both balance and hearing. The inflammation often follows a bacterial ear infection or a viral upper respiratory illness. It may also occur after a blow to the head or may appear with no other associated illness. Signs and symptoms include sudden and intense vertigo that lasts for several days, nausea and vomiting, nystagmus (involuntary back-and-forth movement of the eyes), hearing loss, and tinnitus. If the inflammation is associated with a bacterial infection, a total loss of hearing may result in the affected ear. Treatment generally involves therapy for the original cause.
Meniere’s Disease
Meniere’s is an ear disorder that can affect adults at any age. It is characterized by sudden attacks of vertigo, which may last anywhere from 20 minutes to several days. Nausea often accompanies the condition and is the most common complaint of the condition.
Other signs and symptoms include hearing loss, tinnitus, and a feeling that the affected ear is plugged. Vertigo attacks can be frequent or as little as once a year. Between attacks, no vertigo is experienced although the ability to hear may fluctuate with the attacks and hearing loss will gradually worsen. The disease usually affects only one ear; but, in some people, it can affect both ears.
The exact cause is uncertain, but scientists believe it is associated with fluctuation in the volume and content of the inner ear fluids. Excess fluid can increase pressure on the membranes of the inner ear, distorting and occasionally rupturing them. This can disrupt the sense of balance and hearing.
Treatment generally consists of medications that may, or may not, mask the symptoms but never eliminate the problem. A low-salt diet can help decrease the level of fluid in the body, including the inner ear and may help decrease the frequency of attacks. If dizziness is so severe that it inhibits daily life, inner ear surgery may be considered.
Vestibular Neruonitis
This condition is similar to labyrinthitis in that it causes a sudden onset of vertigo combined with nausea, vomiting, and nystagmus. In fact, the two medical terms are often used interchangeably. Both may be caused by a viral infection.
However, labyrinthitis is an infection of the inner ear, but vestibular neuronitis is an infection of the nerve that leads from the vestibular labyrinth to the vestibular nerve (brain). Because labyrinthitis can also affect the cochlea, it may cause hearing loss; but the inflammation caused by vestibular neuronitis does not.
Signs and symptoms may last for days to weeks, being severe at first and then gradually improving. The attack may occur only once, or it may occur several times over a period of a year or more. Often, vestibular neuronitis will develop after a cold or other upper respiratory viral infection. Most people recover completely from the neuronitis, although some may experience a mild imbalance after the infection has resolved.
Surgery for vestibular disorders is the last resort after medications and rehabilitation therapies have not been successful. Some of the more common surgical procedures for vestibular disorders include:
- patching a tear in either the oval window or the round window leading from the middle ear to the inner ear (perilymph fistula)
- placing tissue over a tear at the top of one of the semicircular canals (superior semicircular canal dehiscence)
- moving a blood vessel that may be pressing up against the vestibular nerve
- draining excess fluid (endolymphatic shunt surgery). This is performed by draining a sac of fluid (endolymph) that resides near the mastoid bone. Sometimes, endolymphatic decompression surgery is performed, which allows more expansion of the endolymphatic sac
- cutting the vestibular nerve (vestibular nerve section). The nerve is cut before it joins the auditory nerve to form the eighth cranial nerve. This has the benefit of potentially preserving your hearing while eliminating vertigo. This surgery may be a reasonable option for a younger person with severe symptoms of Meniere’s disease and no other significant medical problems
- destroying the inner ear (labyrinthectomy). This is a relatively simple operation with fewer risks than in vestibular nerve section. Because it involves destruction of the labyrinth, it is usually reserved for those who have no usable hearing in the affected ear. After surgery, the brain gradually compensates for the loss of inner ear balance on that side by relying on the unaffected ear for all balance information.
