How Audiologists Assess Balance Function
Summary of a public talk given at a BC Balance and Dizziness Disorders Society meeting at St. Paul's Hospital in Vancouver on September 18, 2013.
Speaker: Jolene Harrington
Jolene Harrington is a registered audiologist with the College of Speech and Hearing Health Professionals of BC and is a full member of BCASLPA and CASLPA. Since receiving a master's degree in audiology from the University of British Columbia (UBC) in 2008, Jolene has worked as a clinical audiologist. After a course on VNG/ test administration in Chicago, Jolene has been providing vestibular assessment and management services at St. Paul's Hospital in Vancouver since 2009.
Why go to an audiologist?
Audiologists test hearing - what does hearing have to do with balance? The inner ear includes not only the hearing organ but also the semicircular canals that are part of the balance system. Thus it makes sense for audiologists to assess balance and not just hearing.
What does an audiologist test?
Audiologists assess balance function through a variety of tests including videonystagmography (VNG). This is the main assessment performed by Jolene at St. Paul's. The VNG testing can assist in determining the cause of dizziness. It is done with the patient wearing special goggles fitted with cameras that track eye movements. The tester is looking for nystagmus - an involuntary movement of the eye - which is an indication that something is wrong with the balance system.
VNG assessments are comprised of three parts:
- Ocular motor testing - tests a patient's ability to focus on stationary and moving targets.
- Positional testing - patients are basically flipped around on a bench into different positions while the audiologist looks for abnormal eye movements that indicate loose crystals in the inner ear. The audiologist can often manipulate the patient's head to move the crystal back where it belongs.
- Caloric testing - warm and cold water - 7 degrees above or below body temperature - is poured into the patient's ear while they're wearing the goggles. If the balance sensor is working properly, it will be stimulated and the patient will feel dizzy.
Vestibular evoked myogenic potential (VEMP) testing tests a particular part of the inner ear balance sensor that used to be our hearing organ before we were land animals. This test indicates a bone thinning or hole above the balance sensor; patients with this problem get dizzy when they hear loud sounds or experience changes in pressure.
The balance system is so complex that current technology is still unable to test everything. Sometimes test results may be normal; however, unfortunately, this doesn't necessarily mean that everything is normal.
It is important for the audiologist to get a case history from the patient and perform a hearing test as well as give the vestibular assessments. These all work towards a getting a management plan for the patient, keeping in mind that the balance system is very complex. Sometimes there is more than one cause for a balance problem, thus patients may be looking at more than one type of treatment.