Physicians at the clinic conduct clinical research to learn more about vestibular function in people who suffer from balance disorders such as Ménière's disease, migraine-associated vertigo, and viral inner-ear diseases. Several ongoing studies will provide insight to help improve therapies.
In addition, we are conducting research into chronic, disabling disequilibrium after Ramsay-Hunt syndrome and Meniere’s disease.
The clinic employs doctoral-level audiologists who conduct comprehensive vestibular testing that, until recently, was not possible.
- Videonystagmography (VNG)/ caloric testing
- Rotational chair
- Vestibular-evoked myogenic potential testing
VNG/caloric testing is the standard for measuring vestibular function. It allows for a bilateral comparison of the vestibular responses induced by bithermal irrigations, as well as measuring spontaneous, gaze, and positional nystagmus. Through computerized recording of the saccadic, smooth pursuit, and optokinetic eye movements, we are also able to assess the integrity of the central structures of the vestibular-oculomotor pathways.
While the VNG/Caloric test allows us to identify asymmetry of function between the two sides, the stimulation parameters are such that it mimics only slow head movements. This limits the VNG/Caloric test to assessing one aspect of the vestibular system, and, therefore, some cases of peripheral vestibular dysfunction may be missed by the test.
Rotational Chair Testing
Rotational chair testing tests the vestibular system at higher, more natural, frequencies. The individual sits in a chair which is capable of rotating around a vertical axis. When the chair is rotated in the dark, it induces nystagmus. The individual's eye movements are recorded during this rotation, and the velocity of the slow phase of the nystagmus is compared to the chair rotation at a variety of frequencies to derive a measure of the gain, or function of the vestibular system. The gain can be compared to established norms to determine if there is vestibular hypofunction or hyperfunction.
When tested at higher velocities of rotation, it is possible to determine a measure of asymmetry (or unilateral weakness). In addition to these measures of vestibular system gain, the rotational chair test also allows us to determine the duration of the vestibular response through measures of the time constant. The interaction of the gain and time constant measures are useful in determining whether the vestibular loss is an acute or chronic condition. A prolonged vestibular response may also be found in individuals who suffer from motion sickness. This finding in this particular population can be used to design a treatment program to alleviate the motion sickness. Rotational chair testing is also the most useful method to document bilateral vestibular loss.
Vestibular Laboratory Contacts
David M. Kaylie, MD