Part 2 of 3
    Last month we discovered that dizziness is more common than most people think. In fact, it’s the second most common complaint people bring to their doctors (lower back pain is first). It’s estimated that as many as 40% of all adults experience dizziness severe enough to warrant reporting it to their doctors. Diagnosing dizziness can be complex, and the process usually requires several tests. In most cases, you’ll start with a detailed medical history and a physical examination. Because the balance system is located primarily in the inner ear, a hearing test is a common diagnostic procedure, as is eye movement testing.
The diagnostic process
    The more specific you can be about when your dizziness began, when episodes are most likely to occur, and what sensations you experience, the more information your physician will have to develop an accurate diagnosis.
 Sometimes, a specific cause for dizziness can’t be identified. But, by eliminating the more serious possibilities, you and your physician can confidently manage your symptoms and enable your body’s self-correcting capabilities to take effect. The diagnostic process is both an art and a science ––a partnership between you, your physician, and any other specialists, typically an audiologist, enlisted for diagnostic support.
The anatomy underlying eye movement testing
 Although your balance system is located primarily in the inner ear, it is connected with the brain and brainstem, the eyes, and the sensory nerves throughout your body. Each of these centers sends and receives messages that permit you to maintain your balance. When a disorder is present, these messages cause you to feel abnormal dizziness. One clearly measurable sign of what’s going on with your balance system is a rapid, involuntary eye movement called nystagmus.
By stimulating the nervous system in various ways that usually affect balance, and then carefully measuring your eye movements, your physician can learn much about any abnormalities in your vestibular system. This procedure is called an ENG, which is typically performed by an audiologist. ENG, or electronystagmography, is the recording of eye movements from electrical signals. This is a common test requested, following the hearing test, to further investigate the inner ear balance mechanism. With advancement in today’s diagnostic procedures, it is not the last piece of the puzzle.
A series of tests for a wealth of information ENG is really a group of tests that can contribute significantly to the information your doctor needs to diagnose your dizziness. One test is the saccade test, which looks at rapid side-to-side eye movements. Another is the pursuit test, to measure your ability to follow moving targets. A positioning maneuver test is performed for motion-induced dizziness. Caloric tests involve introducing warm, and then cool, air or water into the ear; and then measuring the resulting changes in eye movement.
If testing is performed via ENG, electrodes are placed near the eyes, to carefully monitor your eye movements. For some of the tests you will be seated, observing light targets whose movements are precisely planned and controlled to evoke normal or abnormal eye movements. For other procedures, such as the caloric test, you will be lying down. The entire sequence usually takes about 45 minutes. Each contributes distinct, valuable information to your overall diagnostic picture, which may not be available through any other means.
    Part 3 — Next Month: Other tests to investigate the cause of dizziness.