Time course of saccade recovery in the VOR analyzed by video head impulse test

Introduction:

The video-head impulse test (V-HIT) allows to estimate the function of the vestibulo-ocular -reflex (VOR) separately for each side, especially the function of the high-frequency-sensible vestibular hair cells. Even small functional lesions can be detected. In this study it is asked, if and how deficits of the VOR, measured by V-HIT, recover.

Methods:

50 consecutive (31 men, 19 women) patients with unilateral or bilateral deficits of the VOR, diagnosed by the appearance of pathological saccades in the V-HIT, were examined. The sample comprised different diseases, the most frequent was the neuropathia vestibularis. The time windows of observation differed from 1 month to 75 months (mean 18,8 months). The chosen parameter was the evidence of correction saccades. The amplitudes were not taken into account, because they can vary with the strength of the stimulus.

Results:

The time course of deficits in the VOR shows two patterns: no change (n = 30), so no recovery, or a delayed appearance of saccades till to a complete disappearance (n = 20).

Conclusions:

An important part of patients with VOR deficits shows recovery. Although the VOR is a three neurons reflex arc with a central synapse, we understand the recovery of the VOR not as a sign of central compensation, but as a sign of a recovery at the level of the receptor, that is the high frequency sensible vestibular hair cells. The prolongation of the latency indicates that the lesion diminishes until a correction saccade is not necessary any more.

Publication History

Publication Date:
23 April 2019 (online)