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525022 research-article 2014

AOR XXX10.1177/0003489414525022Annals ofOtology,Rhinology&Laryngology Croake et al Reprinted by permission of Ann Otol Rhinol Laryngol. 2014; 123(4):271-278.

Article

Annals of Otology, Rhinology & Laryngology 2014, Vol. 123(4) 271–278 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/0003489414525022 aor.sagepub.com

Reliability of Clinical Office-Based Laryngeal Electromyography in Vocally Healthy Adults

Daniel J. Croake, MM, MS 1 , Joseph C. Stemple, PhD 1 , Timothy Uhl, PhD 1 , Sanford Archer, MD, FACS, FAAOA 2 , and Richard D. Andreatta, PhD 1

Abstract Objective: This study aimed to conduct a 3-session reliability assessment of the laryngeal electromyography (LEMG) signal in healthy participants during intensity controlled vocalization tasks. We hypothesized that vocal intensity level and testing session would affect LEMG measures. Methods: This prospective study used a 2-factor repeated measures design. Seven participants underwent bipolar needle LEMG of the right thyroarytenoid muscle. Data were collected over 3 testing sessions using vocalization tasks performed with visually guided intensity feedback targets (65 and 75 dB SPL). Root mean square amplitudes in microvolts were analyzed for within-session and between-session reliability. Results: The main effect for intensity was found to approach significance ( F = 5.71, P = .054). However, intraclass correlation coefficients (ICCs) using a 2-factor mixed random effect model indicated poor to fair signal reliability between testing sessions (ICC = 0.56 at 65 dB, 0.40 at 70 dB). Intraclass correlation coefficients for within-session data indicated excellent reliability for all testing conditions (0.84–0.98). Conclusion: Using a quantitative analysis protocol to inform an essentially qualitative technique, our results indicated that there was generally poor to fair reliability in the LEMG signal over testing sessions. Vocal intensity was an important variable that affected LEMG signal reliability. Standardization of LEMG protocols using vocal control parameters and quantitative analyses may help improve LEMG reliability in clinical settings.

Keywords LEMG, motor units, neuromuscular, thyroarytenoid

Introduction Laryngeal electromyography (LEMG) is commonly used for the assessment of neuromuscular disorders of the lar- ynx. 1 Laryngeal electromyography is the only direct mea- sure of laryngeal muscle activity, and although it provides general information about the function of the laryngeal musculature, its in-office clinical utility beyond general appreciation of gross neuromuscular function is debat- able. 2,3 Studies regarding clinical usefulness of LEMG have not addressed the question of LEMG reliability both within a patient and across clinical testing sessions. Nonclinical and experimental investigations using LEMG have the advantage of signal processing software, control of environ- mental conditions to reduce electromagnetic field noise, tasks that provide graded control of laryngeal muscle recruitment, and less constrained time frames under which to perform LEMG. Because many variables may affect LEMG reliability, it remains unknown whether clinical office-based LEMG, often performed qualitatively, without

vocalization control parameters and under less than optimal recording conditions, can be considered a reliable and clini- cally meaningful diagnostic tool. Laryngeal electromyography has been used for research and assessment of the function of the intrinsic laryngeal muscles for more than 60 years and has been shown to be useful in revealing the function of the laryngeal muscula- ture and demonstrating the dynamic control of this muscu- lature during voicing. 4-7 Laryngeal electromyography is frequently used in conjunction with stroboscopic/ 1 College of Health Sciences, University of Kentucky, Lexington, Kentucky, USA 2 College of Medicine, University of Kentucky, Lexington, Kentucky, USA Corresponding Author: Daniel J. Croake, MM, MS, Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, Room 120H Wethington Building, 900 South Limestone Street, Lexington, KY 40536- 0200, USA. Email: djcroa2@uky.edu

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