Normative vestibulo-ocular reflex data in yaw and pitch axes using the video head-impulse test

oleh: Narges Naderi, Fahimeh Hajiabolhassan, Saeed Farahani, Nasrin Yazdani, Shohreh Jalaie

Format: Article
Diterbitkan: Tehran University of Medical Sciences 2016-05-01

Deskripsi

Background and Aim: The video head-impulse test (vHIT) measures the vestibulo-ocular reflex (VOR) driven by each semicircular canal, follo­wing high-acceleration head rotations. The main measurable response is the ratio of eye mov­ement velocity to the angular head velocity, which reflects canal function. Although norma­tive data is available for VOR gain, most studies only report horizontal VOR characteristics, ignoring variations in vertical plane VOR gains. The purpose of this study was to establish nor­mative data for future comparisons of vesti­bulopathy patients. Methods: Vestibulo-ocular reflex gain and refi­xation saccades were assessed across 50 healthy individuals between the ages of 20 and 64, without any previous or current vestibular dis­orders, by applying and measuring horizontal and vertical head impulses. Results: The mean VOR velocity gain was 0.96 (SD=0.11) and 0.93 (SD=0.17) for the hori­zontal and vertical canals, respectively. The variation of the gain in right anterior/left pos­terior and left anterior/right posterior move­ments appeared to be wider than in the laterals, but the results were not influenced by direction (p>0.05). Refixation saccades occurred in 7.2 percent of all impulse trials, with a majority occurring covertly in lateral canals. Unlike saccades (more often observed in subjects older than 50), the VOR velocity gain varied independently of age. Conclusion: The findings suggest these gain values can be used to determine VOR deficits in patients. vHIT values are affected by diff­erent factors, especially in the vertical plane, so further study is needed to confirm normal ranges of vertical vHIT values.