The Usefulness of Rectified VEMP.
- Author:
Kang Jin LEE
1
;
Min Soo KIM
;
Eun Jin SON
;
Hye Jin LIM
;
Jung Hwan BANG
;
Jae Goo KANG
Author Information
- Publication Type:Original Article
- Keywords: Vestibular evoked myogenic potential; Rectification; Amplitude
- MeSH: Contracts; Dietary Sucrose; Fatigue; Head; Humans; Individuality; Jaw; Lifting; Muscles
- From:Clinical and Experimental Otorhinolaryngology 2008;1(3):143-147
- CountryRepublic of Korea
- Language:English
- Abstract: OBJECTIVES: For a reliable interpretation of left-right difference in Vestibular evoked myogenic potential (VEMP), the amount of sternocleidomastoid muscle (SCM) contraction has to be considered. Therefore, we can ensure that a difference in amplitude between the right and left VEMPs on a patient is due to vestibular abnormality, not due to individual differences of tonic muscle activity, fatigue or improper position. We used rectification to normalize electromyograph (EMG) based on pre-stimulus EMG activity. This study was designed to evaluate and compare the effect of rectification in two conventional ways of SCM contraction. METHODS: Twenty-two normal subjects were included. Two methods were employed for SCM contraction in a subject. First, subjects were made to lie flat on their back, lifting the head off the table and turning to the opposite side. Secondly, subjects push with their jaw against the hand-held inflated cuff to generate cuff pressure of 40 mmHg. From the VEMP graphs, amplitude parameters and inter-aural difference ratio (IADR) were analyzed before and after EMG rectification. RESULTS: Before the rectification, the average IADR of the first method was not statistically different from that of the second method. The average IADRs from each method decreased in a rectified response, showing significant reduction in asymmetry ratio. The lowest average IADR could be obtained with the combination of both the first method and rectification. CONCLUSION: Rectified data show more reliable IADR and may help diagnose some vestibular disorders according to amplitude-associated parameters. The usage of rectification can be maximized with the proper SCM contraction method.
