How to Uncover the Covert Saccade During the Head Impulse Test.

OBJECTIVE: The appearance of "covert" saccades in the head impulse test in patients with vestibular loss may lead to diagnostic misinterpretations. Here, we demonstrate a procedure that can convert covert eye saccades to overt when performing the head impulse test. PATIENTS: Patients with known vestibular deficits that have covert saccades during head impulse test. INTERVENTION: Diagnostic: random and sudden changes of the amplitude (degree of head turn) when performing the head impulse test. MAIN OUTCOME MEASURE: Evaluation of bedside test with video recording and registration from video head impulse test (v-HIT). RESULTS: A video recording and registration from v-HIT that demonstrate the covert saccades of a subject and how the overt saccade is uncovered by changing the amplitude of the head impulse. Five cases are briefly presented. CONCLUSION: By performing the head impulse test with random amplitudes, overt saccades may become detectable and advance accuracy in bedside diagnosis of vestibular deficits.