Effect of Electrical Stimulation on Vestibular Compensation in the Unilateral Labyrinthectomized Rats

Kang, Jun Myung; Yoon, He Ro; Chae, Sayong; Bang, Choong Ill; Lee, Chang Hoon; Lee, Heung Youp

Abstract

BACKGROUND AND OBJECTIVES
The effect of electrical stimulation (ES) on vestibular compensation was investigated for 28 days after unilateral labyrinthectomy (Lx) in 24 rats. MATERIALS AND METHOD: The rats were divided into 4 groups and were treated as follows: A) Lx only, B) Lx with ES (0.6 mA) for 2 days, C) Lx with ES (0.6 mA) for 7 days, D) Lx with ES (1.2 mA) for 2 days. ES with pulse wave (10 Hz) was applied to temporal portion bilaterally (8 hr/day). Cathodal currents were transmitted to the electrode on the destructive side, anodal to that on the intact side. Postoperatively, spontaneous nystagmus (SN) was recorded with the video camera and yaw and roll head tilt (YHT, RHT) were measured using photo images. Horizontal vestibulo-ocular reflex (VOR) was evaluated at various frequencies (0.05, 0.1, 0.5, 1, 2, 3 Hz with peak angular velocity of 40degrees/sec) with the magnetic search coil system. Locomotor movement was monitored with a video camera. RESULTS: The ES groups showed faster compensation in SN, YHT, and RHT than the Lx group. At 3 days after Lx, the ES groups showed significant improvement in the gain over the whole frequency and asymmetry at low frequency compared to that of the Lx group. But the ES group had no effect on compensation of gain and asymmetry on and after 7 days of post-labyrinthectomy. There was no significant difference in vestibular compensation with respect to duration and intensity of ES. ES had no significant effect on the mean velocity and mean deviation of locomotor movements. CONCLUSION: These results suggest that ES has a favorable effect on the suppression of early static symptoms but has no effect on the compensation of dynamic symptoms after the recovery of resting discharge of the vestibular nuclei neurons.