Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

12-2010

Committee Chair or Co-Chairs

Owen Murnane, Ronald H. Baisden

Committee Members

Faith Akin, Uta Schambra

Abstract

The vestibular evoked myogenic potential (VEMP) has been shown to be clinically useful in providing diagnostic information regarding the function of the otolith receptors, inferior vestibular nerve, and vestibulospinal pathways. The VEMP is a biphasic response elicited by loud clicks or tone bursts and recorded from the tonically contracted sternocleidomastoid (SCM) muscle. Because the VEMP is an inhibitory response, it is important to investigate stimulus and parameter characteristics in order to determine the optimal test protocol and maximize clinical usefulness. The aims of this study were 1) to evaluate the effects of 4 different methods of SCM muscle activation and the effect of visual biofeedback on VEMP latency, amplitude, asymmetry ratio, mean rectified EMG level, and difficulty ratings, and 2) to determine the influence of SCM muscle activation pattern and visual biofeedback level on test-retest reliability. Forty-eight healthy volunteers between the ages of 18 and 50 underwent VEMP testing using each of the following muscle activation patterns: supine with the head raised (SE), supine with the head turned away from the test ear (SR), supine with the head raised and turned away from the test ear (SER), and sitting with the head turned away from the test ear (SitR). Testing subjects with the SER method yielded the most robust amplitude response and sternocleidomastoid EMG activity. No statistically significant differences were found in interaural asymmetry ratios among the 4 methods of SCM activation. Subjects rated the SE and SER methods as more difficult than the SE and SitR methods at each of the 3 target levels. Test-retest reliability was high for P1/N1 amplitude and mean rectified EMG levels when subjects were provided visual biofeedback to monitor the level of tonic SCM muscle activity. The study demonstrates the importance of providing patients a means of monitoring and maintaining the amplitude of the rectified EMG at a constant target level during SCM muscle activation. Although no evidence to reject or strongly favor a specific method was found, monaural-ipsilateral recording with the SitR method was found to be advantageous for individuals with weakness or decreased endurance for sustained muscle contraction.

Document Type

Dissertation - Open Access

Copyright

Copyright by the authors.

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