Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Graduation

5-7-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Communication Sciences and Disorders

Advisor(s)

Erin G. Piker

Christopher Clinard

Christopher Zalewski

Abstract

Cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs, respectfully) are considered objective tests of vestibular function measured using surface electromyography (EMG). In addition, VEMPs are visually detected by an examiner, often requiring a high level of stimulation to the ear to easily visualize a waveform plotted across time. However, a high level of stimulation, like those used during routine VEMP testing, is problematic since it has been shown to be unsafe in children when compared to adults. Visual interpretation can also vary between examiners in cases of reduced vestibular function or when the level of required muscle contraction is low. One method to alleviate the burden of visual detection is to use objective detection algorithms – introduced as an alternative to visual detection of the auditory brainstem response (ABR). An algorithm known as fixed single point (Fsp) estimates the signal-to-noise ratio (SNR) and statistically determines if a response is present. Fsp has multiple clinical applications including a profound impact on the identification of hearing loss; yet, our understanding of how this algorithms behaves in VEMPs remains limited.

The purpose of this investigation was to characterize the behavior of Fsp in cVEMPs and oVEMPs and compare Fsp to visual detection in a group of young healthy participants. Air-conducted cVEMPs and oVEMPs were elicited using 500 Hz tonebursts. For both responses, the effect of stimulus level on Fsp was assessed. For cVEMPs, the additional effect of EMG activation was assessed by varying EMG targets between 10 – 150 µV.

When applied to VEMP detection, Fsp values increased as stimulus level increased in cVEMPs and oVEMPs, however Fsp values remained significant at lower stimulus levels. In cVEMPs, Fsp values were comparable across different levels of EMG activation and maximum EMG activation did not yield larger Fsp values. Finally, Fsp was comparable to visual detection when detecting VEMP threshold. These results showed the feasibility of Fsp when applied to VEMPs and have the potential to shift conventional thinking about the role of stimulus level and muscle contraction during routine VEMP testing.

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