Detection of peripheral vestibular disorders by the pendular rotation test in cats

Unilateral vestibular disorders were induced in 3 cats by means of the injection of a small amount of sodium hydroxide into the middle ear, and vestibulo-ocular responses (VOR) to various kinds of pendular stimulation were investigated at 1 week and at 1, 2, 3, 4, and 5 months after the operation. The pendular rotation test was performed at frequencies of 0.025, 0.1, 0.25 and 0.5 Hz, and peak velocities of 50, 100, 150, and 200 degrees/s, and the directional preponderance of the VOR gain (DP%) was measured using a computer. DP% 1 week after the operation was still very high at each frequency and velocity of the stimulation. On the other hand, DP% more than 1 month after the operation had decreased markedly, although it increased with an increase in the velocity of stimulation at all frequencies except at 0.5 Hz, and DP% at a velocity of 200 degrees/s was still high even 5 months later. This suggests that high velocity pendular stimulation should be used to detect unilateral vestibular disorders.