The VNG test assesses the vestibular function of the inner ear and helps determine if a disorder in the vestibular system is contributing to a patient's dizziness or imbalance. For this test the patient must wear a pair of goggles which records eye movements. The test has three main parts:
- Ocular mobility testing entails following a moving dot with your eyes to look for any slowness or inaccuracies in your ability to follow visual targets.
- Positional testing looks at eye movements during different positions of moving the head and body.
- Caloric testing involves stimulating both ears with warm and then cool air. This change in temperature stimulates the inner ear which in turn causes reflex movements of the eyes.
From the three main parts of VNG, eye movements are recorded and measured. Analyzing these eye movements reveals how well the balance mechanism is functioning and may indicate if a central or neurological problem or problem in the inner ear exists.
Rotational Chair Testing
The rotational chair testing is typically done in conjunction with the VNG test and measures whether or not a disorder of the inner ear may be contributing to a patient's dizziness and imbalance. For this test, electrodes are placed near each eye and on the forehead. The patient is rotated slowly back and forth in the test chair, which is located in a darkened room. Unlike the VNG test, the rotational chair test is able to assess both the right and left ears at the same time to determine how they are working together.
Vestibular Evoked Myogenic Potential (VEMP) Testing
VEMP testing assesses a portion of the vestibular system separate from those of the VNG or rotational chair testing. During VEMP testing, electrodes are placed on the neck muscles and insert earphones are placed in the ears. The presentation of the stimulus through the headphones produces a response that is measured from the neck muscle.