Another tool we have for the study of vertigo of vestibular origin is the Video Head Impulse Test (vHIT), which allows us to evaluate the vestibulo-ocular reflex (VOR). Thanks to this reflex, we are able to keep the images we see stable during our daily movements. When a patient presents vertigo due to unilateral vestibular hypofunction, corrective saccades will appear on the affected side.
vHIT Goggles
The vHIT helps to quantify VOR gain and to detect saccades that are invisible to the naked eye.
The test itself is a simple procedure that usually takes no more than 10 minutes to perform. The patient sits 1–1.5 meters from a visual target on the wall (a sticker), and the goggles are placed and adjusted. These goggles are very lightweight and, for that reason, must be fitted very snugly to prevent slipping during head movements. When the goggles are fitted, a brief automatic calibration procedure is performed. Once calibrated, the patient is asked to fix their gaze on the target on the wall, trying not to blink.
vHIT procedure
At this point, the test begins, consisting of generating head movements to the right and left. Approximately 20 random impulses toward each side are required to complete the test. Once the test is finished, the recorded results appear on the screen. On one side, there is a diagram showing the gain of each head impulse performed, and on the other, a representation of head and eye movements for each turn.
Who is the Video Head Impulse Test (vHIT) indicated for?
The test is indicated for any patient in whom unilateral or bilateral vestibular hypofunction is suspected. Its result is independent of the condition of the external and middle ear and is especially useful in patients for whom caloric vestibular testing is contraindicated.