Detection of Vestiular Lesional Side by Passive Impulsive Head Rotation Testing

A passive impulsive head rotation test was performed to evaluate the affected side of the labyrinth.A device reported by Tokita (1993) was used to record head and eye movements. Displacements and velocities of head and eye movements were respectively recorded by terrestrial magnetism sensor and an electronystagmographic technique. To examine vestibulo-ocular response (VOR), passive impulsive head rotations to the right and left at irregular intervals were performed repeatedly similar to the maneuver reported by Halmagyi et al (1993). From the record, latency and VOR gain ratio (VOR gain on the affected side rotation/VOR gain on the healthy side rotation) at 40ms and 80ms after onset of head rotation were measured.Twenty-two patients with unilateral vestibular disorders were examined in this manner. The affected side of the labyrinth was determined by caloric test.Seventeen patients showed VOR gain ratios less than 0.8 indicating hyporeaction of the affected labyrinth. Three patients including one with a slight canal paresis on caloric test showed ratios within 1±0.2. Two patients including one with a prolonged course showed ratios greater than 1.2. Examination of the VOR gain ratio on passive impulsive head rotation was a useful rotation test to evaluate the affected side of the labyrinth.