sections include: what causes dizziness?, diagnosis
When we experience dizziness—an often confusing and difficult-to-describe sensation—it is because we are no longer certain of our position or motion in space, something that we ordinarily take for granted. To know where we are in space and how we are moving depends on accurate, reliable, and rapid perception by five senses:
- Vision, which uses the horizon and vertical objects for coordinates.
- Vestibular sensations from the inner ear, which perceive both angular acceleration, as when we turn our heads rapidly, and linear acceleration, such as gravity or the motion of a car as it gains speed.
- Touch and pressure sense, which identifies our weight pressing on the soles of our feet or the seat of our pants. Proprioception, which detects the movements of our limbs and neck.
- Hearing, which orients us to sound-emitting and sound-reflecting objects.
Our brains integrate these sensations to give us a complete picture of where we are and how we are moving. We rapidly and continually repeat the process of perceiving our environment, integrating the sensations, and moving appropriately. With this feedback of information, and appropriate motion in response, we can walk, run, cycle, or skate smoothly. As infants, we develop this process in our first years until it becomes so natural that we are rarely aware of it, or need to make conscious adjustments. When this “feedback loop” is disrupted for any reason, however, we can experience dizziness—due to our uncertainty of position or motion in space—and we may feel unsteady and light-headed, move awkwardly, or lose our balance.
When people say they feel dizzy, their symptoms can be of four quite distinct types:
- True rotational vertigo—a spinning sensation.
- A feeling as if you are about to faint, called presyncope.
- Disequilibrium, or unsteadiness of gait and balance without abnormal feelings in the head.
- Light-headedness—a vague, abnormal head sensation other than types 1–3.
Dizziness can be a spontaneous sensation, occurring without relation to position or motion, or it can be triggered by standing or certain movements, positions, or situations.
What Causes Dizziness?
Dizziness is either a complaint or a symptom, like pain or fever, and it has many possible causes. In fact, more than 60 different disorders can cause dizziness, including many conditions involving the brain, inner ear, heart, blood vessels, lungs, and other organs. In this section some of the more common neurological causes are discussed.
We start with two disorders that affect the inner ear and cause vertigo. They can occur at all ages.
Benign Paroxysmal Positional Vertigo
Benign paroxysmal positional vertigo (BPPV) is one of the most common conditions causing vertigo, and certainly the most easily treated and cured. A person with BPPV experiences vertigo—a sensation of rotation—on changing position, especially when lying on one side, rolling over in bed with the affected ear down, or reaching up to put something on a high shelf. The vertigo of BPPV is often described as spinning and may be violent; it usually lasts 30 to 45 seconds and can be accompanied by nausea or vomiting. If a person changes, then resumes, the provoking position several times, the vertigo diminishes on subsequent movements, but the susceptibility to vertigo returns after a short rest interval.
BPPV is due to the movement of tiny calcium carbonate crystals (otoliths) from a part of the inner ear where they are normally present (the utricle) to a part where they are not (the posterior semicircular canal). This condition can be easily cured in less than ten minutes with the “Epley canalith repositioning maneuver”: a physician trained in the maneuver moves the person through a series of four positions in order to roll the otoliths back into the utricle.
Ménière’s disease is due to the excessive accumulation of the normal endolymphatic fluid in the inner ear, usually on one side only. Three symptoms occur with Ménière’s disease: vertigo,hearing impairment, and tinnitus (ringing in the ear). Typically, attacks of vertigo recur several days to several years apart, while hearing often fluctuates but declines over time.
To relieve the vertigo, a doctor can prescribe medications that suppress peripheral (inner ear) or central (brain stem) vestibular function, such as meclizine and some benzodiazepines. Three medications also cause drowsiness, and methylphenidate is helpful to reduce that side effect. A variety of surgical procedures can relieve the fluid pressure but are not consistently effective. Some people with Ménière’s disease benefit from steroids. If the attacks of vertigo become frequent and disruptive, a physician can stop all vestibular function in the inner ear (and therefore all vertigo arising from that ear), without further damaging hearing, by injecting certain aminoglycoside antibiotics (gentamicin) into the ear canal.
Many elderly patients, especially those with diabetes, experience multisensory dizziness due to a combination of visual impairment, peripheral neuropathy, arthritic changes (especially in cervical joints), and often impaired inner ear function and hearing. When we lack the necessary sensations to know precisely where we are, or how rapidly and in what directions we are moving, we may experience dizziness when in motion, and feel much more stable when sitting, lying, or leaning against a stationary object.
Treatment for multisensory dizziness involves helping a person learn to use the senses that are intact more effectively. People who have been wearing bifocals can benefit from using singlevision distance glasses so they can look down for orientation. Using a cane that is dragged rather than lifted can provide additional balance clues. If cervical arthritis is a contributing factor, a soft cervical collar can help by limiting neck movements. Physical therapy with gait training, and other exercises to improve balance, can also be useful.
When people with orthostatic hypotension stand up, their blood pressure falls, resulting in insufficient blood flow to the brain, and they may feel faint. This can be due to multiple system atrophy (also known as Shy-Drager syndrome), which is a disorder involving the autonomic nervous system. Other symptoms of multiple system atrophy include Parkinsonism, unsteadiness of gait, impotence, and peripheral neuropathy. Physicians can treat the low blood pressure with fluorohydrocortisone or midodrine. Occasionally symptoms improve with nonsteroidal anti-inflammatory drugs (NSAIDs).
Strokes (ischemic, hemorrhagic) may cause vertigo when they involve the areas of the brain stem to which the inner ear sends signals—the vestibular nuclei. Nearly all people with this problem also have additional neurological symptoms and signs, such as facial numbness or weakness, clumsiness, or weakness of a limb, and so on. In transient ischemic attacks, in which blood flow to a part of the brain is diminished or stops temporarily, the same symptoms may last minutes to hours, then disappear. That experience is a warning that one is at risk for a stroke. Strokes are more easily prevented than treated; see ischemic strokes for preventive steps, such as controlling blood pressure, reducing cholesterol, and not smoking.
Among young adults, panic state, agoraphobia, and hyperventilation syndrome are common causes of dizziness. Panic state and agoraphobia produce severe nonrotational dizziness, often in crowded places (supermarkets, cocktail parties, elevators, and so forth). This problem can lead people to avoid these settings, becoming reclusive. The disorder can be treated with certain benzodiazepine tranquilizers; some of the antidepressant selective serotonin reuptake inhibitors (SSRIs), such as paroxetine; and behavior modification. Treatment is often quite successful.
Hyperventilation refers to breathing too deeply or rapidly, thereby reducing the normal amount of carbon dioxide in the body. People who hyperventilate are usually anxious or depressed, or may have panic attacks. They are rarely aware of hyperventilating, however; typically they sigh deeply and frequently. The loss of carbon dioxide causes their cerebral blood vessels to constrict and produces a feeling of type 4 dizziness—that is, light-headedness without vertigo. While the effects of hyperventilation can be frightening, most people can learn to recognize their onset and take preventive steps (including rebreathing into a small plastic bag) when an attack begins.
Dizziness can also result if a person is excessively aware of normal sensation. Our five senses are capable of perceiving and accurately reporting a broad, but limited, range of physical experiences. When this sensory capacity is exceeded, we normally experience dizziness—for example, on the tilt-a-whirl in an amusement park, or while watching a car chase in a wraparound movie theater. Some people are more sensitive than others to brief, everyday sensations of dizziness and may regard these momentary uncertainties as possibly pathologic. Small doses of methylphenidate can reduce this symptom for some individuals, but most benefit just from understanding that the feeling is normal.
Other possible causes of dizziness include:
- Irregular heartbeat; anemia; hypothyroidism.
- Certain neurological disorders, including multiple sclerosis, Parkinsonism, and diseases involving the cerebellum or frontal lobes.
- Many medications, especially those with sedative or other central nervous system effects (see substance abuse and chemicals).
Treating the dizziness that accompanies these medical problems should always begin by identifying the underlying disease and treating it directly (for example, irregular heartbeat or hypothyroidism).
To determine why a person feels dizzy, the physician must start by taking a detailed neurological and medical history and performing a physical examination focused on the particular causes of dizziness.
Four questions in particular help with the diagnosis:
- How old are you? Certain conditions typically occur at young or old ages: for example, strokes and multisensory dizziness occur in the elderly, while hyperventilation, panic states, and agoraphobia are most common in young women; multiple sclerosis usually affects young adults. Thus, a person’s age suggests some of the most likely explanations for dizziness.
- Do you feel as if you’re spinning? True rotational vertigo indicates a disorder of the inner ear or its brain stem connections.
- Do you feel as if you’re going to faint? Faintness suggests a cardiovascular cause.
- Do you feel unsteady on your feet even though your head is clear? Disequilibrium of this sort is common in patients with neurological disorders affecting balance and coordination.
A person whose complaint is light-headedness may have hyperventilation or a psychiatric disorder, or may have a limited form of one of the other types of dizziness. Because many people have difficulty describing their symptoms accurately, however, the doctor may use a Dizziness Simulation Battery of eight maneuvers that reproduce these varied symptoms, allowing a person to choose the best match for his or her complaint.
Routine laboratory studies for diagnosing the cause of dizziness include a complete blood count, a chemistry survey, thyroid function tests, an electrocardiogram (ECG) with a rhythm strip, an electronystagmogram (inner ear test), an audiogram, and the MMPI, a psychological screening test. Specialized tests that may answer specific diagnostic questions (but are not routine) include an MRI/MRA (magnetic resonance imaging/magnetic resonance angiography) scan, a Holter monitor to evaluate cardiac rhythm, a five-hour glucose tolerance test for hypoglycemia or diabetes, a tilttable (which monitors whether a person can keep a stable blood pressure when tilted from a horizontal to a vertical position), an electroencephalogram (EEG), and a battery of psychological tests.
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