VOR Cancellation at the patient's bedside: how to avoid another cause of false positive

Abstract

There is little literature on the semiological aspects of the clinical Vestibulo-Occulomotor Reflex (VOR) cancellation technique. This study aims to determine which would be the best head movement frequency cutoff to perform the VOR cancellation clinical test. Materials and methods: 98 horizontal semicircular canals with normal gains from normal individuals were included. The VOR was cancelled by placing a headband with a fixed target over the individual's head, and the patient was told to keep their eyes on the target while the examiner recorded the presence and number of saccades that were evident with the naked eye by performing sinusoidal cephalic rotations at different frequencies. The head rotation frequency was compared with the following variables: 1-Saccades that are evident with the naked eye -SHIMP (+) clinical-, 2-The presence of saccades performed for a period of 2 seconds, 3- The presence of saccades performed in every cycle, 4- Amplitude in º/sec. of the performed saccades, 5-Percentage of VOR cancellation and 6-Age. Conclusion: To avoid a false positive caused by SHIMP saccades during the clinical evaluation of the VOR cancellation at the patient's bedside, we recommend performing cephalic rotations with frequencies lower than 0.5Hz - 0.6Hz for the age group under 67 years old. In patients older than and equal to 67 years old, the interpretation of the VOR cancellation using this method should be cautious, and it should be performed with glasses if worn. Keywords: vestibulo-cular reflex cancellation, SHIMP saccades, SHIMP headband