Get access

Quantitative laryngeal electromyography: Turns and amplitude analysis§


  • Melissa McCarty Statham MD,

    1. Division of Pediatric Otolaryngology , Head and Neck Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, U.S.A.
    Search for more papers by this author
  • Clark A. Rosen MD, FACS,

    1. University of Pittsburgh Medical Center Voice Center , Department of Otolaryngology, Head and Neck Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, U.S.A.
    Search for more papers by this author
  • Sanjeev D. Nandedkar PhD,

    1. CareFusion , Middleton, Wisconsin, U.S.A.
    Search for more papers by this author
  • Michael C. Munin MD

    Corresponding author
    1. Department of Physical Medicine and Rehabilitation , University of Pittsburgh, Pittsburgh, Pennsylvania, U.S.A.
    • Department of Physical Medicine and Rehabilitation, University of Pittsburgh, 3471 Fifth Avenue, Suite 201, Pittsburgh, PA 15213
    Search for more papers by this author

  • Presented at the American Laryngological Society April 28, 2010, Las Vegas, NV.

  • The authors declare that they did not receive any financial support.

  • §

    The authors declare that there are no conflicting interests.



Laryngeal electromyography (LEMG) is primarily a qualitative examination, with no standardized approach to interpretation. The objectives of our study were to establish quantitative norms for motor unit recruitment in controls and to compare with interference pattern analysis in patients with unilateral vocal fold paralysis (VFP).


Retrospective case–control study


We performed LEMG of the thyroarytenoid-lateral cricoarytenoid muscle complex (TA-LCA) in 21 controls and 16 patients with unilateral VFP. Our standardized protocol used a concentric needle electrode with subjects performing variable force TA-LCA contraction. To quantify the interference pattern density, we measured turns and mean amplitude per turn for ≥10 epochs (each 500 milliseconds). Logarithmic regression analysis between amplitude and turns was used to calculate slope and intercept. Standard deviation was calculated to further define the confidence interval, enabling generation of a linear-scale graphical “cloud” of activity containing ≥90% of data points for controls and patients.


Median age of controls and patients was similar (50.7 vs. 48.5 years). In controls, TA-LCA amplitude with variable contraction ranged from 145–1112 μV, and regression analysis comparing mean amplitude per turn to root-mean-square amplitude demonstrated high correlation (R = 0.82). In controls performing variable contraction, median turns per second was significantly higher compared to patients (450 vs. 290, P = .002).


We first present interference pattern analysis in the TA-LCA in healthy adults and patients with unilateral VFP. Our findings indicate that motor unit recruitment can be quantitatively measured within the TA-LCA. Additionally, patients with unilateral VFP had significantly reduced turns when compared with controls. Laryngoscope, 2010