Audiologists are concerned with more than just the ears. With an estimated half of all Americans expected to deal with balance problems at some point in their lives, many of these potentially debilitating conditions, there is a strong demand for diagnostic testing and treatment of vestibular disorders. Audiologists are clinically trained to provide these services to patients experiencing dizziness and vertigo in order to help prevent falls and other serious complications resulting from inner ear disorders.
The inner ear serves dual functions: it is responsible for both hearing and balance. It contains the labyrinth, a network of bony fluid-filled tubes divided into three sections—the cochlea, semicircular canals, and vestibule. Sensory information is transmitted from the vestibular system to the brain, and helps the body determine its position in relation to gravity and other objects. Abnormalities in the vestibular system can lead to dizziness, vertigo, and balance disorders such as labyrinthitis, BPPV and Meniere’s disease.
Diagnostic testing is aimed at evaluating the underlying cause of a patient’s dizziness in order to come up with a treatment plan. Audiologists may administer a number of clinical and electrophysiological balance tests to help assess equilibrium. These include any or all of the following:
- Videonystagmography (VNG). Videonystagmography (VNG), the most common (and accurate) type of balance test, is actually a series of individual tests that use an infrared camera to measure involuntary eye movements indicative of a balance disorder. Most VNG tests consist of four parts: a rapid eye movement test, a tracking test, a positional test and a caloric test.
- Vestibular Evoked Myogenic Potentials (VEMP). Evoked potential tests measure electrical activity in the brain in response to external stimuli such as sight, sound and touch. The VEMP utilizes electrodes to measure signals in the brain and can determine whether the nerves of the inner ear are functioning normally.
- Vestibulo-Ocular Reflex (VOR). VOR testing measures reflexive eye movement in response to a rapid movement of the head to one side. It is normal for the eyes to move in the opposite direction of the head in order to stabilize images; a lack of corresponding eye movement when this exercise is performed indicates balance system dysfunction.
- Video Head Impulse Testing (VHIT). VHIT testing utilizes a pair of video goggles to measure eye velocity and record abnormalities in patients exhibiting VOR dysfunction. This allows the audiologist to determine whether a vestibular disorder is the reason for dizziness.
Any patient with unexplained dizziness will benefit from an evaluation comprised of these common balance tests.