There are different aspects of the balance system which can malfunction. In some people the problem is an irreversible injury to the nerves which serve the “gyroscope” of the inner ear, called the vestibular system. Fortunately, the brain has a remarkable ability to recognize when one of the vestibular systems is not working correctly. At first a person with a vestibular “weakness”, or vestibulopathy, feels disoriented and maybe sick to the stomach. With time the brain usually learns to disregard this faulty information. In other words, the brain “compensates” for the problem.
Videonystagmography (VNG) refers to a series of tests that evaluate the contribution of the three systems that keep us in balance, vestibular (inner ear), visual, and the somatosensory (input from contact with the surfaces we are walking on). The brain combines the information from each of these three systems and keeps us in balance as we walk, turn our head, read, drive, etc.
Our window into the balance system are the eyes. Goggles are worn while a series of simple tasks, such as following the movement of a light on a bar, changing head and body positions are performed. A separate portion of the test stimulates the vestibular system directly by delivering warm then cool air into each ear. Information from the tests is combined with other clinical information to determine if the balance disorder is ear related or not. Then a strategy for treating the disorder is formulated. This may include vestibular rehabilitation exercises or referral to other medical specialties.