The Changes of Vestibulo-Ocular Reflex after Acute Peripheral Unilateral Vestibular Loss

Chung, Woon Kyo; Lee, Won Sang; Han, Jae Wook; Chi, Jang Hoon; Hong, Hyun Jung

Abstract

BACKGROUND AND OBJECTIVE: It is well known that compensation begins after acute unilateral peripheral vestibular function loss. The change of vestibulo-ocular reflex (VOR) is variable and affected by many factors. But there is no studies reported on the changes of individuals with the lapse of time. Using the rotation chair test and caloric test, we wanted to know the individual compensatory process of VOR as time progresses following an acute unilateral peripheral vestibular loss.
MATERIALS AND METHODS
Subjects were patients of acute peripheral vestibular neuritis (n=19) whose nystagmus showed more than 24 hours. The follow up period was 10 weeks until the head shake nystagmus (HSN) disappeared. We measured the duration of each spontaneous nystagmus (SN) and HSN. Sinusoidal harmonic acceleration (SHA) was tested at 0.04 and at 0.08 Hz level, with the step velocity of 100 degrees per second. We also performed caloric test after HSN disappeared.
RESULTS
SN and HSN each lasted 25 days and 50 days. VOR changes had an irregular pattern among individuals with gain increasing after decrement and phase lead decreasing after increment. Furthermore, the gain asymmetry was more irregular and lasted longer as well at the step velocity. Even though compensation has been reached, the caloric test revealed continuous abnormal values, which is quite different from the recovery of VOR in the rotatory test.
CONCLUSION
During the early compensation period, we could recognize that the individual VOR changes recovered with a irregular pattern. On the other hand, the caloric test was not altered even after compensation.