The Video Head Impulse Test, or vHIT, is an instrumented technique that is used to help diagnose reduction in vestibular function in one ear versus the other. Using a lightweight, high-speed video goggle to measure left or right eye velocity and record any abnormalities, vHIT gives hearing health professionals the ability to quickly and objectively measure the vestibular ocular reflex (VOR) in response to a patient’s head movements within the normal range of daily motions.
Head impulse testing, in several forms including magnetic-field coil systems, has been available for more than twenty years. The vHIT brings modern technology into the equation to provide immediate information about side-specific vestibular function and the ability to detect covert saccades. The goggles worn by the patient are imbedded with a camera that is capable of high frame rates for capturing eye movement and an accelerometer/gyroscope that captures head movement. Several head impulses are collected during the duration of the test. The results allow the hearing health professional to compare eye and head movement data to look for any signs of VOR loss. At the same time, gain values are calculated automatically through the vHIT software.
In a study published in 2013, MacDougall et al1 recorded video horizontal head impulse test results at 250 Hz and concluded that vHIT was successful in detecting both overt and covert catch-up saccades in all patient groups that were evaluated. The research also concluded that vHIT “is equivalent to search coils in identifying peripheral vestibular deficits ….” They reported that vHIT was easier to use than any of the previous systems, including when working with patients that were experiencing acute vestibular neuritis.
As a leader in the balance screening and diagnostic market, e3 Diagnostics supplies the most cutting-edge vestibular testing equipment available, including the EyeSeeCam vHIT from Interacoustics. This instrument provides fast and objective measurements of the vestibulo-ocular reflex. The test results allow a hearing health professional to effectively assess a “dizzy” patient and determine if their symptoms are caused by a vestibular disorder.
Also available from e3 Diagnostics is the innovative VORTEQ from Micromedical Technologies, designed to provide simple and inexpensive methods to evaluate VOR gain, phase, and symmetry. VORTEQ is available as a standalone system or as an option on the Micromedical VisualEyes VNG.
Not meant as a substitute for the rotatory chair or VNG tests, vHIT is valuable as a complement to those tried-and-true, vestibular testing methods. Where the rotatory chair disseminates low-frequency information, vHIT provides very high-frequency data. Hearing health professionals, after using vHIT, have reported finding substantial levels of VOR loss in patients that had previously been diagnosed as having nothing wrong with their vestibular system.
Investing in a vHIT system to upgrade your practice should involve performing your due diligence prior to purchasing one of the available systems. Be assured that your local e3 Diagnostics representative can offer hands-on demonstrations of vHIT equipment and help you make the correct decision. And, after the purchase, you can rely on your e3 rep to be there to answer any questions and offer input throughout your period of adjustment and beyond.
Interested in learning more about vHIT? Get in touch with your local e3 office today!
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References
1MacDougall HG, Weber KP, McGarvie LA, Halmagyi GM, Curthoys IS (2009) The video head impulse test: diagnostic accuracy in peripheral vestibulopathy. Neurology 73: 1134–1141