The head impulse test (HIT) is a safe and quick way of assessing semicircular canal function in patients with peripheral vestibular loss at the bedside, first described in 1988. This test is practical even in sick patients and needs no equipment. The clinician identifies overt (=visible) catch-up saccades back to the target after passive head rotation as a clinical sign of canal paresis. However, it is known that some patients with absence of vestibular function do not make overt saccades, but instead make covert catch up saccades during the passive unpredictable head turn, which are extremely difficult for the clinician to detect with the naked eye. Recently, a new lightweight, nonslip, high-speed video-oculography system (vHIT; video head impulse test) has been developed that measures eye velocity during head rotations. This system is easy to use in a clinical setting, provides an objective measure of the vestibulo-ocular-reflex (VOR), and detects both overt and covert catch-up saccades in patients with vestibular loss.
