Vestibular Function Testing - What to Expect

Some patients with dizziness and imbalance might need vestibular function testing. Vestibular function testing is a battery of tests to assess the function of all aspects of the vestibular system. When remembering the anatomy of the vestibular system, it is clear why there is no one test to assess the entire apparatus. Therefore, we use the a combination of the following tests to get a clearer idea of the health of the entire system.

Videonystagmography (VNG)

Videonystagmography, or VNG, testing is one of the most common vestibular functions tests patients encounter. This test is usually performed by an audiologist and uses eye movements to assess the function of the vestibular system. Remember our eyes and our vestibular system are intimately linked via the Vestibular Ocular Reflex (VOR). The patient wears video goggles that record specific eye movement while the patient undergoes a series of tests, including:

• Oculomotor exam - how your eyes track an object either on a light bar or TV screen

• Positional testing - how your eyes move in various positions such as laying down or with your head rotated

• Caloric testing - how your eyes move when cold and warm air or water is placed in your ear. This test can be the most provoking test and patients can get quite dizzy. However, that's not necessarily a bad sign! In many cases that means your vestibular system is functioning very well. Here's a short video on what to expect with calroic testing.

Vestibular Evoked Myogenic Potentials (VEMP)

Vestibular Evoked Myogenic Potentials, or VEMP, testing is a test that measure muscle activity to assess the health of the vestibular system. Ocular VEMPs measure eye muscle activity (remember the VOR) and Cervical VEMPs measure neck muscle activity. This is because the vestibular system is also connected to our neck movement via the Vestibular Collic (neck) Reflex and the Vestibular Spinal Reflex (VSR). Here is a video on what to expect form VEMP testing.

Rotational Chair Testing

Some patients will also require further testing using a rotational chair. Patients are seated in the chair, usually in a dark room, and as the chair slowly rotates back and forth, the patient's eye movement is tracked. This testing is the gold standard for determining if you have weakness or loss in both the left and right vestibular system. This is what Rotational Chair Testing looks like.

Video Head Impulse Test

Video Head Impulse Test, or vHIT, is another test that looks at the function of your semi-circular canals and the Vestibular Ocular Reflex (VOR). Remember the semicircular canals sense rotational acceleration. When rotational acceleration is sensed in a specific direction, your eyes move at the same velocity in the opposite direction. This is the Vestibular Ocular Reflex at work! Here is what to expect from vHIT testing.

Subjective Visual Vertical

Subjective Visual Vertical, or SVV, testing assess your vestibular system and brain's ability to discern true vertical in reference to gravity. Here, you are in a dark room and asked to rotate a beam of light to the vertical position without visual reference to your environment.

Computerized Dynamic Posturography

Computerized Dynamic Posturography, or CDP, is another battery of tests to assess your balance. There are three components to CDP testing:

1. Sensory Organization Test (SOT) assesses your brains ability to integrate information from your visual, vestibular, and somatosensory (sensation through your legs) systems to maintain balance. Here's is what the SOT looks like:

   
   

2. Motor Control Test (MCT) assesses your ability to maintain balance when there is an external perturbation or force. In this case, a force plate that unpredictably moves forward or backward from under you. Here's what MCT looks like:

   
   

3. Adaptation Test assesses your ability to maintain balance on a sloped surface. Here, the force plate tilts forward or backward. Here's an example of the Adaptation Test:

   
   

   In the end, vestibular function testing is a great set of tools to help providers hone in on why you may be experiencing dizziness and imbalance. However, it can take 3-4 hours to perform and is not required for every patient. A skilled vestibular therapist can assess most of these aspects of your vestibular system in a 30 minute office visit. However, if more information is necessary to make a diagnosis, they may recommend you get vestibular function testing. Be sure to ask your doctor or vestibular therapist what to expect so you feel prepared and comfortable the day of testing.