Dizziness, Imbalance and BPPV Testing

Dizziness and Imbalance Testing

ENG or VNG Overview:

Electronystagmography (ENG) or Videonystagmography (VNG) is a test of your balance or vestibular system that is located in your inner ears. Both tests examine responses to visual stimuli and positional changes to determine the responsiveness of the balance system in each ear. It is important to note that the vestibular system and visual system are very closely related and those two systems work together to give you your perception of balance. Changes in your vestibular system will result in compensating eye movements and thus we are able to effectively evaluate the health of your vestibular system by looking at your visual responses.

The difference between ENG and VNG tests is the recording method used. ENG utilizes five electrodes placed on the skin around your eyes to record muscle responses from eye movements and VNG utilizes video cameras inside goggles you wear to directly record eye movements. VNG is the preferred test method because it gives us a clear picture of the eye movements, while ENG is a more indirect measure of eye movement. However, in rare cases VNG goggles cannot be used and therefore ENG testing will be done instead.

VNG and ENG testing is mostly done sitting in a chair in a semi-dark room. We do ask that you arrive make-up free and wearing comfortable clothing. If doing a VNG, eye make-up will interfere with the video cameras in the goggles. If doing an ENG, base make-up or powder will interfere with the electrodes. During the test you'll also be asked to change body position and head positions (some examples include moving from sitting to lying down and rolling onto your side and changing head position from looking left to looking right). These movements are easier to achieve if you are wearing comfortable clothing. Intake of certain medications, alcohol, nicotine and caffeine prior to the test can negatively affect the test results so the audiologist will review a set of pre-test instructions to be sure you are not taking anything that would cause problems with the test before the test is scheduled.

The entire ENG or VNG test takes about 90 minutes to complete. The subtests involved in the ENG and VNG test battery can be broken down into the following categories: bedside exam, oculomotor tests, positional tests and caloric tests. Test results will not be immediately available, as most of the subtests require further review. The final ENG or VNG test report will be delivered to the ordering physician within 2 business days of your test and that physician or their representative will call you with the results and treatment plan.

BEDSIDE EXAM:

The bedside exam starts with a thorough case history assessment. You will be asked many questions about your dizziness symptoms that include when the symptoms began, the duration the symptoms typically last, how the symptoms make you feel, what situations cause the symptoms to worsen, and what you do to help ease the symptoms. Some patients find it helpful to bring along a spouse or close friend to help them answer these questions. The bedside exam also consists of several vestibular screening assessments that evaluate your ability to maintain your balance, your ability to move your eyes together, your ability to move your head and neck, and your perception of vertical (up or down).

OCULOMOTOR TESTS:

The oculomotor tests evaluate your ability to correctly follow a visual stimulus. The visual stimulus used is a red dot. Different oculomotor subtests evaluate the speed and accuracy of your eye movements compared to the movements of the red dot, your ability to focus correctly on a stable red dot in different positions, and your ability to accurately follow multiple moving red dots. These tests give us information on how your visual system is communicating with your vestibular system.

POSITIONAL TESTS:

The positional tests involve moving you into different positions on our exam table and evaluating the message your balance system sends regarding those positional changes through various eye movements. If we are able to identify that you are experiencing a specific type of positional vertigo called benign paroxysmal positional vertigo (BPPV), a simple repositioning maneuver to treat that condition will be done following the completion of the ENG or VNG test.

CALORIC TESTS:

Caloric tests consist of irrigating each ear with warm and cool water. The irrigations last around 30 seconds per irrigation and most patients report a sensation of movement following the irrigation that lasts for just a few minutes. The movement sensation is typically very slight. The caloric tests tell us how responsive the vestibular system is in each ear. Our brain depends on equal input from the right and left ear vestibular systems for our sense of balance.

Testing for Benign Paroxysmal Positional Vertigo (BPPV)

BPPV is a condition where particles, called otoconia or calcium carbonate crystals, inside the otoliths (balance organs sensitive to gravity and acceleration) get displaced inside one of the semicircular canals in the inner ear. This causes a brief and sometimes intense feeling of vertigo or dizziness that occurs when a person moves in a way that stimulates the semicircular canal with the displaced otoconia. BPPV can be easily identified in the office with a simple test where the patient is placed in positions that stimulate the different semicircular canals. If the symptoms can be provoked while in the office, we can identify the canal that has the displaced particles and can do a series of simple maneuvers to get those otoconia to move out of the semicircular canal.

Patients typically feel much better after one maneuver, called a canalith repositioning procedure (CRP), but in some cases, a repeat CRP may need to be scheduled approximately one week later to achieve full resolution of symptoms. In rare cases of bilateral BPPV, a condition where otoconia are displaced in semicircular canals in both the left and right ears, we have to treat the side that has the most severe symptoms first and then the opposite side can be treated once the symptoms have resolved on the original side treated.