1993 Volume 52 Issue 3 Pages 461-465
We developed a new type of rotatory chair system to examine vertical semicircular canal-stimulative postrotatory nystagmus in normal ears. The subjects sat on the rotatory chair with their heads and backs tilting backward 60 from the vertical line, and their heads at 30°, 45°, or 60°to the plane of rotation. The rotation was performed with an initial acceleration of 10°/sec 2 for 10 sec and a terminal acceleration of 100° or 180°/sec 2 following a period of constant velocity for 20 sec in each position with either clockwise or counter-clockwise rotation. In this position, we were able to examine isolated excitatory single canals for all four of the vertical semicircular canals. The postrotatory nystagmus was analyzed with an infrared video recording system. There were no remarkable differences in the maximum slow phase eye velocity and the duration of postrotatory nystagmus between terminal acceleration of 100°/sec 2 and that of 180°/sec 2. Moreover, there were no obvious differences in the balance of nystagmic reactions, after stimulative rotation for the anterior or posterior semicircular canal, between the left and the right sides.
However, the degree of postrotatory nystagmic reaction in each posterior semicircular canal was usually much more than that in each anterior semicircular canal in most normal subjects.
