title: Quantitative laryngeal electromyography: turns and amplitude analysis.
abstract: OBJECTIVE
  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).
  
  
  METHODS
  Retrospective case-control study
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Pediatric Otolaryngology, Head and Neck Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 15213, USA.
authors.forename: Melissa McCarty
authors.initials: MM
authors.lastname: Statham
authors.forename: Clark A
authors.initials: CA
authors.lastname: Rosen
authors.forename: Sanjeev D
authors.initials: SD
authors.lastname: Nandedkar
authors.forename: Michael C
authors.initials: MC
authors.lastname: Munin
mesh_terms: D016022:Case-Control Studies; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D012008:Recurrence; D012044:Regression Analysis; D012189:Retrospective Studies; D014826:Vocal Cord Paralysis / Q000209:etiology / Q000503:physiopathology*