Videonystagmography, or VNG, is a diagnostic test used to determine if inner ear functions are the cause of dizziness and balance disorders. Interestingly, VNG is a series of tests that examine the involuntary movement of the eyes known as nystagmus, to monitor and diagnose problems with the ears. The movements are recorded through infrared cameras in the form of goggles placed over the eyes. The only discomfort from this comprehensive exam comes as a result of wearing goggles. VNG is one of the only tests that can determine if the problem is unilateral, related to one ear, or bilateral, related to both ears.
Types of VNG Tests
The VNG exam measure the movement of the eyes in a variety of situations and include the following varieties of tests:
The gaze test records eye movements as the patient looks straight ahead, to the left, to the right, up and down with eyes open and closed. This test looks for the presence of nystagmus, or involuntary motion.
The saccades test records eye movement as the patient looks back and forth between two horizontal points, as in reading. This test looks for defects of saccadic eye movement.
Pendular Tracking Testing
Pendular tracking testing records eye movement as the patient follows a moving visual target. This test looks for abnormalities of pursuit eye movement.
With the optokinetic test, eye movements are recorded as the patient looks at vertical stripes moving at different speeds. This test determines the presence of nystagmus, which becomes stronger as stimulus speed increases.
During the positional test, the patient's head and body are moved into various positions and the eyes are then recorded while both open and closed to detect the presence of any nystagmus.
With the hallpike maneuver, the patient's head is moved rapidly and the presence of any nystagmus is checked after each movement.
During the caloric test, each ear is irrigated with air or water above body temperature and then below body temperature. This test provokes nystagmus and then examines the responses of each ear to determine if one vestibular mechanism is more sensitive than the other.
While this test is comprehensive, it is completely non-invasive with no side effects. Patients can drive themselves home immediately following the exam. A doctor will determine whether a VNG test is appropriate for diagnosing each patient's condition.