Balance depends on the central nervous system and our ability to integrate input from the inner ear, eyes, muscles and sensations of the lower extremities. Each year, one-third of adults over age 65 experience dizziness, balance problems or falls. Falls are the leading cause of injury in older adults. Five-percent of all falls lead to fractures and can be disabling.
Vestibular and inner ear disorders. These may cause intermittent or constant dizziness. Neurological problems. These include multiple sclerosis, Parkinson’s disease, stroke, head injury, spinal cord injury, amputation and neuropathy. Orthopedic injuries or procedures such as spine injuries or total joint replacement Decreased strength and flexibility secondary to inactivity. These factors can decrease the sense of balance and affect balance reactions. Medications. Some may cause dizziness or disequilibrium.
While one of the most common reasons for visits to doctor’s offices (~10 %) this symptom is probably one of the most vague. When not permitted to use the word dizzy to describe their sensation, patients will describe feelings such as light headedness (as though about to faint), giddiness, depersonalization (the feeling that they are outside their body) or a sense of turning, spinning or rocking. Sometimes it is a sensation inside the head and other times related to problems with balance.
When the symptoms are described using words like “woozy”, “about to black out”, “tunnel vision”, or “lightheaded”, “a pre-syncopal” (about to faint) association is suggested. This is almost always due to insufficient blood flow to the brain. In general, symptoms are worse when standing and improve with lying down. This kind of dizziness is frequently experienced by healthy individuals who rise quickly from a chair, often after a meal, and have a few seconds of disorientation.
Another cause of dizziness is related to various physiological conditions often associated with anxiety. Overbreathing (hyperventilation) can cause lightheadedness and a sense of unsteadiness, as well as tingling around the mouth and fingertips. This can be relieved by breathing in and out of a paper bag to increase the level of carbon dioxide in the blood.
Vertigo is a term reserved for a sense of motion, when the body is really at rest. Most often, vertigo is experienced as a spinning sensation like that experienced after getting off of a merry-go-round. Linear motion or rocking motions are also described.
Angular motion (turning) is sensed by the inner ear balance mechanism, specifically the semicircular canals (pictured on the top of the home page). There are three canals in each ear, so motion in three dimensions can be detected. Each canal is like a bicycle tire inner tube filled with fluid (endolymph). At one point, however, there is a membrane (cupula) which goes across the inside of the tube attached to the inner wall. This membrane is flexible enough to be deflected by any movement of the fluid in the tube. Just as an ice cube in a glass of water stays in the same place if the glass is turned, the fluid inside the canal tries to remain stationary even if the tube is turned as happens during a head movement, since the canals are really tunnels in the temporal bone of the skull. So when the head turns, the cupula is pushed up against a column of endolymph which is at rest, and is deflected. There are special (hair) cells which detect this bending and alter the signals going into the brain (via the eighth cranial nerve). There are also contributions from the visual system and sensation from the body which can influence the perception of motion.
The cupula has its own blood supply, whereas the endolymph is made by cells which pull fluid from the bloodstream and secrete it into the canals. When someone drinks alcohol, it is absorbed into the blood, making it more dilute, or less dense (lower specific gravity) than usual. Now imagine, for instance, the horizontal semicircular canal sitting in the inner ear. As our overindulgent imbiber lays down in the barcolounger, the canal becomes oriented such that the cupula is about at 3 o’clock. The cupula, which is surrounded by endolymph (most of which was made prior to the firstdrink) is filled with the dilute blood. Normally, the cupula is neither heavier nor lighter than the endolymph, and doesn’t try rise or sink. However with less dense blood inside, it floats up in the denser endolymph, deflecting the cupula as during head rotation, and causing the same signal change in the nerve to the brain, which it incorrectly interprets as a spinning motion. But our unfortunate reveler is not out of the woods yet. The endolymph produced while under the influence is itself influenced by the specific gravity of the blood when it was made. Several hours after he bars close, and the first bout of spinning is over, the blood is back to its normal specific gravity, or even a bit denser if the drinker is, as is often the case, a bit dehydrated. The endolymph, however, is a little less dense than usual, reflecting the state of the dilute blood when it was made. So now the cupula will sink in the endolymph, and the spinning, although perceived in the opposite direction as before, is back until blood and endolymph again become equilibrated to their normal specific gravity.
Warning signs associated with stroke and dizziness includes double vision, numbness or clumsiness on one side of the body, hiccups that won’t go away, unequal pupils and jaw weakness. How can a physician determine if dizziness is due to a vestibular problem? Dizziness is a symptom, something of which the sufferer is aware, prompting a complaint to the physician. Vertigo, a symptom, is frequently associated with a sign, something an examining physician can observe. A sign of vertigo can be ataxia (walking as though intoxicated) with a tendency to turn to one side. A very important finding is a type of eye movement called nystagmus. From the Greek word meaning to nod, these movements consist of a drift of both eyes in the same direction followed by a rapid movement in the opposite direction. One can’t really observe these movements in oneself (except with a video camera) but they are easily observed in others; simply watch the eyes of someone looking out of a car window at the scenery moving past.
Benign Paroxysmal Positional Vertigo (BPPV)–a brief, intense sensation of vertigo that occurs because of a specific positional change of the head. An individual may experience BPPV when rollingover to the left or right upon getting out of bed in the morning, or when looking up for an object on a high shelf. The cause of BPPV is not known, although it may be caused by an inner ear infection, head injury, or aging. Labyrinthitis–an infection or inflammation of the inner ear causing dizziness and loss of balance. Ménière’s disease–an inner ear fluid balance disorder that causes episodes of vertigo, fluctuating hearing loss, tinnitus (a ringing or roaring in the ears), and the sensation of fullness in the ear. The cause of Ménière’s disease is unknown. Vestibular neuronitis–aninfection of the vestibular nerve, generally viral. Perilymph fistula–a leakage of inner ear fluid to the middle ear. It can occur after head injury, physical exertion or, rarely, without a known cause.