Video Head Impulse Test- An Overview

By Author: Alok Gupta
Total Articles: 6
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The video Head Impulse Test (vHIT) integrates a new technology that uses a high pace, lightweight video frenzel goggle system to measure eye velocity and record catch up quick simultaneous movements and other abnormalities in patients with impaired vestibular ocular reflex (VOR) function. This test provides a quick and objective measure of the vestibular ocular reflex in response to head movements in the natural range of daily motions. The test results in vHIT give way or yield instant information regarding side-specific vestibular function. It allows the healthcare professionals to efficiently assess the dizzy patient and quickly decide if the dizziness is related to a vestibular disorder.

Head impulse testing (HIT) in various forms using several protocols has been available for more than twenty years. In its simplest form, the head impulse test provides fast, consistent, bedside screening of semicircular canal (SCC) function with no equipment needed. It also allows a three-dimensional analysis with respect to the three pairs of semicircular canals, and Head impulse testing complements other traditional vestibular tests. ...
... Magnetic-field coil systems or search coil techniques were previously used as the gold standard to determine and record head impulse testing. These systems included 2 or 3 magnets worn similar to contact lenses to gauge eye position in tandem with head position. Search coils were technically challenging and not easy to use. They were also expensive and time-consuming, and slippage plus comfort made them unlikely to be used in routine clinical practice.

Later after many studies and efforts, it was found that video horizontal head impulse test is successful in detecting overt and covert catch-up saccades (quick simultaneous movements) in all patient groups assessed. It was also found that vHIT is equivalent to search coils in identifying peripheral vestibular deficits and it is easier to use than previously used systems, and also when working with patients experiencing acute vestibular neuritis. It was seen and reported that vHIT results using a camera while recording 250 frames per second attached on a lightweight spectacle to prevent slippage of the camera relative to the head. It determined corrective saccades overt as well as covert and were easily detectable in patients with reduced horizontal canal vestibular ocular reflex gain when delivering manually graded head impulses and then objectively analyzing the stimulus-response characteristics of the VOR. vHIT was noted to be easy and practical to apply.

To check the validity of vHIT, subjects were tested. The subjects’ heads were rotated rapidly in the horizontal plane. Eye movements were recorded via VOG goggles to enumerate eye and head movements and to calculate gain as a ratio of angular eye velocity to angular head velocity. Their results revealed VOR gain measurements were reliable and comparable to the previous search coil method.

Now, in the present day, video head impulse test is extensively used to determine the related disorders. It has gained momentum and popularity in the medical world and has helped immensely in diagnostics and research.