Reply to the response by Dr. S. J. Xie

Excerpt

I appreciate Dr. Xie’s interest to our letter [1]. However, Dr. Xie’s response contains misunderstanding and confusion. First of all, I did not conclude that oVEMP reflects utricular functions while cVEMP reflects saccular functions. I presented a patient who was considered to show that oVEMP to 500 Hz air-conducted short tone bursts (STB) could reflect functions of different vestibular population than cVEMP to 500 Hz air-conducted STB. As one of explanations of this finding, I proposed the hypothesis that oVEMP might reflect utricular functions while cVEMP might reflect saccular functions. I also proposed an alternative explanation. Of course, other explanations also should be considered. Although Dr. Xie hypothesized that oVEMP related 500 Hz STB-sensitive saccular afferents might be different from cVEMP related 500 Hz STB-sensitive saccular afferents, it is physiologically unlikely and there is no available clear evidence. Although Dr. Xie cited my previous paper concerning cVEMP to STB and clicks [2], that paper has nothing to do with the current issue, because in the current case [1], we recorded oVEMP and cVEMP using the same stimulation (500 Hz air-conducted STB). Dr. Xie also pointed out that we did not perform subjective visual vertical (SVV) tests or SVV tests with eccentric rotation. I agree that these tests are good tests for otolith function assessment. However, results of these tests are not conclusive. Even though one utricle had damages, these tests could be normal because of vestibular compensation [3]. Even though these tests were abnormal, the results would not definitely point out the abnormal side. Finally, I want to emphasize that the most important point at the current stage is to prove sound-sensitivity of utricular afferents to air-conducted sound neurophysiologically. …