Active Head Impulse Test

Active head impulse test (HIT): instruct the patient to fix their eyes on the camera and turn their head 20o to the right/left, and then make a rapid movement toward the midline to align their head with the camera again, keeping their eyes fixed on the camera throughout. A simple instruction is to ask the patient to move the head from the initial eccentric position back to a neutral position as quickly as they can. The test can also be completed with rapid movements away from the midline (thus making the maneuver less predictable for the patient - however, it is not clear that one method is superior to the other for the purposes of the active HIT). In the case of an acute right peripheral vestibulopathy (e.g., vestibular neuritis), a rightward HIT will result in the eyes moving to the right with the head initially, so that a corrective re-fixation saccade will be needed to move the eyes back to the target, or to the left. This is considered an abnormal or positive HIT and generally suggests a peripheral process (although there are exceptions). Note that a mildly abnormal HIT may not be detectable virtually, as patients may struggle to achieve the same rapid velocity of head movement and rapid deceleration that are controlled by the examiner during the passive bedside HIT (https://collections.lib.utah.edu/details?id=187678). Also, the unpredictability of the passive (bedside) HIT makes it more challenging for patients to make compensatory (covert) saccades during the head movement. Even a patient with known severe vestibular loss may or may not have an abnormal active HIT (see example - https://collections.lib.utah.edu/ark:/87278/s6d84xrj).