2022 年 81 巻 1 号 p. 16-21
The Video Head Impulse Test (vHIT) is an excellent technique for evaluating the function of the vertical semicircular canals, in addition to that of the lateral semicircular canals.
vHIT to evaluate the function of the lateral semicircular canals involves the use of a single method (the neck is rotated on around the yaw plane), and there is little difference in result by the difference of the model the results are scarcely affected by differences in the model used. However, testing of the vertical semicircular canals by vHIT is more difficult, and the test method differs depending on the vHIT model used.
There are two EyeSeeCam (ESC) methods used to determine the functioning of the vertical semicircular canals. One is to rotate in the pitch direction in head while watch the mark in the front of subject after 45 degrees made it rotate on yaw plane In the first, the head is abruptly rotated around the yaw axis up to 45 degrees in the pitch direction while the subject watches the mark in front of him. In the other, is head rotating on the head is rotated in the stimulation reception plane of each vertical semicircular canal while watch the mark in the front of subject the subject is asked to fix his/gaze on a mark in front of him. In generally, the examiner chooses the method that is easier to use. In Japan, ICS impulse (ICS) is also used for vHIT, besides ESC.
Testing of the vertical semicircular canal function test by ICS is done by a single method to rotate in the pitch direction in head after 45 degrees made it rotate on yaw plane: the head is rotated around the pitch axis after it is rotated 45 degrees around the yaw plane.
The results of testing of the vertical semicircular canal function could vary according to the device model used, and the method was unified so that we thought it would be desirable to unify the method of stimulation.
As a preliminary step to unify the stimulation methods, we examined the effect of the difference between the two types of vertical semicircular canal stimulation methods by ESC.
Subjects were healthy subjects without dysequilibrium. Using ESC, on the same day, the examiner examined the lateral semicircular canal function test and the vertical semicircular canal of two kinds. We compare with an obtained gains of the Vertical canal of two kinds. There were no differences in the results of testing of the vertical semicircular canal function between the two stimulation methods in the test of either the vertical or horizontal semicircular.