The vestibular system in the inner ear is the primary sensory system when it comes to balance. If this system malfunctions, the patient will likely experience balance problems such as vertigo. When this happens, an audiologist can test the vestibular system using videonystamography (VNG) or electronystagmography (ENG) methods. These tests can determine the health of the balance system and which ear may be affected.
With VNG, goggles are placed over the eyes with wires that connect them to a computer. The goggles contain a camera that monitors eye movement. With ENG, electrodes placed beside each eye also monitor eye movements and send results to a computer. The computer analyzes the eye movements and the results are interpreted by an audiologist to determine if problems are present with the vestibular system.
There are three parts to the test. First, the patient sits up in a chair and watches moving lights. The purpose of this is to assess the visual system. Second, the patient lies back and moves their eyes while in various head and body positions. This assesses the effect changing orientation has on the patient. Third, the patient lies back at an angle. Short bursts of warm and cool air are blown into the patient’s ear. The purpose of this is to assess the balance system.
The purpose of VNG and ENG is to test the vestibulo-ocular reflex. This system in the eye and inner ear generates eye movements that maintain steady vision when the body, particularly the head, is moving. VNG and ENG can detect if there is a disconnect between the ocular and visual systems.