An in vivo model of external superior laryngeal nerve paralysis: laryngoscopic findings.
OBJECTIVE
For over 100 years, a controversy has existed regarding the laryngeal signs that should be considered pathognomonic of unilateral external superior laryngeal nerve (ESLN) paralysis. By selectively blocking the ESLN using lidocaine, we attempted to identify the salient laryngeal features associated with acute, unilateral cricothyroid (CT) muscle dysfunction.


METHODS
Prospective, repeated measures, experimental design.


METHODS
Ten vocally normal adult males underwent lidocaine block of the right ESLN with laryngeal electromyography verification. Flexible videolaryngostroboscopic (FVLS) recordings were acquired before and during the block. Eleven blinded, expert judges, rated randomized pre- versus during block recordings of 10 vocal tasks using standardized FVLS rating protocols.


RESULTS
Contrary to recent clinical reports, no evidence of hypomobility/sluggishness of the ipsilateral vocal fold, or a consistent pattern of axial rotation of the larynx was observed. Instead, the analysis revealed: 1) deviation of the petiole of the epiglottis to the side of weakness in 60% of participants during a glissando up maneuver produced at normal volume, and 2) axial rotation of the posterior commissure to the left and the anterior commissure to the right in 50% of participants during a maneuver which rapidly alternated between a maximum vocal fold abduction task (sniff) and a high-pitched "ee" production.


CONCLUSIONS
Neither of these laryngeal findings has been reported previously. They potentially represent valuable diagnostic markers of acute, unilateral CT paralysis. Clinical populations need to be explored to better appreciate the diagnostic value and precision of these laryngeal signs.
Department of Communication Sciences and Disorders, the University of Utah, Salt Lake City, Utah 84112-0252, USA. nelson.roy@health.utah.edu
Nelson
N
Roy
Michael E
ME
Barton
Marshall E
ME
Smith
Christopher
C
Dromey
Ray M
RM
Merrill
Cara
C
Sauder
D000328:Adult; D004576:Electromyography; D006801:Humans; D007821:Laryngeal Muscles / Q000294:innervation*; D007823:Laryngeal Nerves / Q000187:drug effects / Q000503:physiopathology*; D007828:Laryngoscopy; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D009407:Nerve Block; D011446:Prospective Studies; D014826:Vocal Cord Paralysis / Q000139:chemically induced / Q000503:physiopathology*
D008012:Lidocaine