Clin Exp Otorhinolaryngol.  2013 Dec;6(4):209-213.

Capacity of Rectified Vestibular Evoked Myogenic Potential in Correcting Asymmetric Muscle Contraction Power

• Kim KW
• Jung JY
• Lee JH
• Suh MW

Abstract

OBJECTIVES
Rectified vestibular evoked myogenic potential (rVEMP) is new method that simultaneously measures the muscle contraction power during VEMP recordings. Although there are a few studies that have evaluated the effect of the rVEMP, there is no study that has evaluated the capacity of rVEMP during asymmetrical muscle contraction.
METHODS
Thirty VEMP measurements were performed among 20 normal subjects (mean age, 28.2+/-2.1 years; male, 16). VEMP was measured in the supine position. The head was turned to the right side by 0degrees, 15degrees, 30degrees, and 45degrees and the VEMPs were recorded in each position. The interaural amplitude difference (IAD) ratio was calculated by the conventional non-rectified VEMP (nVEMP) and rVEMP.
RESULTS
The nVEMP IAD increased significantly according to increasing neck rotation. The IAD in rVEMP was almost similar from 0degrees to 30degrees. However, the IAD was significantly larger than the other positions when the neck was rotated 45degrees. When IAD during 0degrees was set as a standard, the IAD of the rVEMP was significantly smaller that the nVEMP only during the 30degrees rotaion.
CONCLUSION
Rectified VEMP is capable of correcting asymmetrical muscle contraction power. In contrast, it cannot correct the asymmetry if muscle contraction power asymmetry is 44.8% or larger. Also, it is not necessary if muscle contraction power asymmetry is 22.5% or smaller.

Keyword

Rectified vestibular evoked myogenic potential; Muscle contraction power; Otology; Vestibular diseases

MeSH Terms

Head
Humans
Male
Muscle Contraction*
Muscles*
Neck
Otolaryngology
Supine Position
Vestibular Diseases

Figure

• 

  Fig. 1 Position of the subject to induce asymmetric muscle contraction. First, the ceiling was marked for 0°, 15°, 30°, and 45° rotations. The vestibular evoked myogenic potential (VEMP) was measured in the supine position while the head was elevated 2 cm from the bed. The head was then turned towards the right at 0°, 15°, 30°, and 45°. The VEMP was recorded in each position.

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  Fig. 2 Asymmetry between right and left muscle contraction power. The asymmetry of muscle contraction power increased in a linear pattern as the head was turned more towards the right side. This difference was quantified with the following formula: muscle contraction power asymmetry (%)=(left muscle contraction power-right muscle contraction power)/(left muscle contraction power+right muscle contraction power)×100.

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  Fig. 3 Interaural amplitude difference (IAD). The IAD of non-rectified conventional vestibular evoked myogenic potential (nVEMP) increased as the head rotation angle increased but plateaued at 30° and 45° (A). IAD during asymmetric muscle contraction (15°, 30°, and 45°) was significantly different from the 0° condition. The IAD of rectified VEMP (rVEMP) was stable with minimal differences from 0° to 30°, but significantly increased at 45° (B).

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  Fig. 4 Relative increase in interaural amplitude difference ratio (ΔIAD). In order to quantify the perturbation of IAD solely due to asymmetric muscle contraction, the IAD at 15°, 30°, and 45° was compared with that at the 0° condition. The ratio of IAD at each position relative to 0° was expressed as ΔIAD (ΔIAD=IAD at each position / 0° IAD). The ΔIAD of rectified conventional VEMP was significantly smaller than that of the non-rectified conventional VEMP at 30°. VEMP, vestibular evoked myogenic potential.

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