Electronystagmography(ENG) is an indispensable otoneurologic test with which we can record the eye movements. However, because its results are greatly influenced by the various test conditions, it is very important to establish the standard test
method
and normal data of their own laboratories.
Authors performed several vestibular function tests using ENG on 20 normal volunteers and the following results were obtained.
1) The calibrating amplitude of 20 degrees in eye movement was 26.5μV in average. In calibration test, the overshoot was noted in 11 of 20 subjects and was 4.1% in average. The undershoot was noted in 9 of 20 subjects and was 3.5% in average.
2) In sinusoidal eye tracking test with frequencies of 0.33, 0.42, 0.50, 0.58 Hz, significant differences were not present between the eye speed of both directions(p>0.05) and the gains were 0.85, 0.90 and 0.95 respectively.
3) In optokinetic nystagmus test with target velocity of 18, 23 and 32deg/sec. of both directions, significant differences were not present between the slow phase eye velocities(SPEV) of right and left direction and gains were 0.37, 0.39 and
0.38,
respectively. Optokinetic after nystagmus was observed in 9 of 20 subjects, among which the average duration was 8.1 seconds and average SPEV was 2.0 deg/sec.
4) In bithermal caloric test, the average latency of nystagmus was 29 seconds and the average duration was 119 seconds and the average SPEV 60 seconds after caloric stimulation(60-sec SPEV) was 28.4 deg/sec. We observed that the negative
correlation
was present between latency and duration(r=-.6064) and the positive correlation was present between duration and maximum SPEV (r=.5484).
5) The SPEV of 40, 60 and 80 seconds after caloric stimulation were 20.9, 28.4 and 21.6 deg/se, respectively, which showed 60-sed SPE was the greatest among them, Unilateral vestibular weakness and directional preponderance, calculating from
nystagmus
duration, 60-sec SPEV and maximum SPEV did not show significant differences. The average suppression of 60-sec SPEV by ocular fixation(Fixation Index) was 67%. Nystagmus frequency before and after ocular fixation was 28.8/sec, and 37.7/sec, which
showed
significant increase of frequency of ocular fixation(p<0.01).
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