Balance disorders, particularly those of vestibular origin, can cause dizziness, vertigo, imbalance, unsteadiness, rocking, tilting, blurred vision, nausea and/or falls. Identifying the exact cause of the disorder often requires diagnostic testing in order to make the proper diagnosis. As such, your doctor may order any number of the following evaluations to help determine the cause.
Balance disorders are often accompanied by changes in hearing, tinnitus (ringing in the ears) or aural fullness. As such, your evaluation may begin with testing of the outer, middle and inner ear. These tests are carried out in a sound-treated room with a set of headphones which also allow voice contact with the audiologist through a microphone.
ENG/VNG is a group of tests that look for signs of vestibular dysfunction or neurological deficits by measuring nystagmus and other physiologic responses. ENG/VNG tests are the most common procedures administered to people with dizziness, vertigo, and/ or balance disorders, although the test protocol and methodology may vary. The first ENG/VNG subtest evaluates the movement of the eyes as they follow specific targets. The second subtest observes eye movement as the head is positioned in different directions. And lastly, during the caloric test, warm and/or cold water or air is circulated in the ear canal to test the vestibular response stimulated by the temperature change.
Rotational tests are another way of evaluating how well the eyes and inner ear work together. For every head movement in one direction, there is eye movement in the opposite direction. With rotational tests the examiner can record eye movement while the head is moving at various speeds. This provides additional information, beyond the ENG/VNG, about how well the balance organs are functioning. Not all people will need rotational tests.
VEMP testing is used to evaluate whether the saccule and the inferior vestibular nerve are intact and functioning normally. During VEMP testing, insert earphones are placed in the ears and small electrodes are attached to the skin over the neck muscles. When sound is transmitted through the earphones, the electrodes record the response of the muscle to the vestibular stimuli. VEMP are useful at identifying canal dehiscence (SCCD), fistulae and enlarged vestibular aqueduct (EVAS) among other conditions.
CDP tests postural stability. While ENG/VNG and rotation tests assess visual-vestibular interactions, CDP provides information about motor control or balance function under varying environmental conditions. This is important because the ability to maintain balance depends not only upon sensory information from the vision and the vestibular systems, but also on sensory information that the brain receives from the muscles and joints. These somatosensory signals provide clues such as the direction of head turn and the texture and slope of the walking surface. CDP tests the relationships among these three sensory inputs and records the balance and posture adjustments made by a person in response to variations in reliable information provided by the vision and somatosensory systems. This test involves standing on a platform, typically with some form of visual target to watch. The platform and/or the visual target move while pressure gauges under the platform record shifts in body weight (body sway) as the person being tested maintains balance. A safety harness is worn to prevent falling during the test. Posturography gives information about how well balance is maintained during challenging situations. It can help doctors plan other vestibular testing, as well as assist in treatment design.
ECoG measures how sound signals move from the ear along the beginning of the hearing nerve. An EcoG involves the patient lying still and listening to a series of clicks while surface electrodes measure the response. This test is useful in evaluating for cochlear hydrops.
The ABR measures how hearing signals travel from the ear to the brain and then within parts of the brain. Under certain circumstances, this test can indicate the presence of an acoustic neuroma (a rare, benign tumor of the vestibulo-cochlear nerve). It may also help identify conditions such as multiple sclerosis if they have affected the auditory pathway to the brain.
Most balance problems can be treated medically, surgically or with therapy once they have been accurately diagnosed. Rehabilitation therapy is now successfully reducing or eliminating dizziness, vertigo and unsteadiness for many patients.