Parameters of Normalcy of Video Head Impulse Test Responses: Preliminary Results
Introduction: The video Head Impulse Test (vHIT) assesses and detects possible dysfunctions of the each one of the six semicircular canals (CSC) by measuring the eye-movement response to head impulse.
Objective: To determine the parameters of vHIT responses in normal subjects.
Methods: It evaluated 21 subjects, aged between 20 and 58 years, 5 men and 16 women. All underwent vHIT, computed Otometrics ICS Impulse, with the use of lenses with high-resolution and speed camera that gets the eye-movement response to head impulses in the lateral and vertical planes in this sequence Right lateral-Left Lateral (Lateral), Right Anterior-Left Posterior (RALP) and Left Anterior-Right Posterior (LARP). They used as values of speed: 100 to 250 degrees per second for lateral impulses and 50 to 200 degrees per second for vertical impulses.
Results: The mean values of the gain for right and left lateral CSC, right anterior, left posterior, left anterior, and right posterior were 1.00 , 0.99, 1.00, 0.99, 0.91, and 0.87, respectively, with a standard deviation: 0.078, 0.072, 0.115, 0.072, 0.095, and 0.105. The asymmetry was 3% compared to the synergistic pairs (CSC laterals, RALP, and LARP) of left and right ears, with a standard deviation of 0.018, 0.028, and 0.035, respectively.
Conclusion: The normal gain for the laterals must fall between 1.16 and 0.83, and for the verticals, it should fall between 1.23 and 0.66 in 95% of cases. The asymmetry varies from 0.00to 14%.
Keywords: neurotology, video Head Impulse test, vertigo.