Background. Denervation of skeletal muscle typically results in irreversibl
e denervation atrophy over time. This finding has generated controversy as
to the efficacy of reinnervation procedures for chronic vocal fold immobili
ty related to recurrent laryngeal nerve injury. Objective: To test the hypo
thesis that chronic vocal fold immobility after recurrent laryngeal nerve i
njury does not result in diminished maximal isometric force generation in t
he thyroarytenoid muscle. Study Design: Adult random-bred cats underwent ei
ther unilateral laryngeal denervation (n = 6) or sham surgery (n = 6). Afte
r 6 months, videolaryngoscopy was performed followed by in vitro measuremen
t of maximal isometric tetanic force produced by the thyroarytenoid muscle.
Results: All animals in the denervation group showed right vocal fold para
lysis after the initial denervation operation; none of these animals had re
turn of appropriately phased movement with respiration. Four had intermitte
nt disorganized twitching movements. One had these movements plus an occasi
onal weak adduction, and one had no movement. Normal vocal fold mobility wa
s observed in 6 of 6 animals undergoing sham surgery. The maximal isometric
tetanic force measured from the thyroarytenoid muscle in the sham group wa
s 438 MN (+/- 92 mN standard deviation [SD]). The maximal isometric tetanic
force measured from the thyroarytenoid muscle in the chronically immobile
group was 405 mN (+/- 107 mN SD). Differences were not statistically signif
icant. Conclusion: Maximal isometric force in the thyroarytenoid muscle is
not diminished in chronic vocal fold immobility after recurrent laryngeal n
erve injury. We conclude that the possibility for restoration of contractil
e force to the chronically immobile thyroarytenoid muscle exists. This find
ing supports the pursuit of reinnervation procedures in the treatment of ch
ronic vocal fold immobility.