Local neurotoxins for prevention of laryngeal synkinesis after recurrent laryngeal nerve injury.
OBJECTIVE
Persistent vocal fold motion impairment after recurrent laryngeal nerve (RLN) injury is not characteristically due to absent reinnervation, but often results from spontaneous aberrant reinnervation (synkinesis). We administered local neurotoxins to selected laryngeal muscles after RLN injury to determine whether aberrant reinnervation could be selectively inhibited.


METHODS
Unilateral RLN transection was performed in 24 male rats. Three weeks later, the denervated laryngeal adductor complex was injected with phenol, high- or low-dose vincristine sulfate (VNC), or saline solution. One month later, rat larynges were evaluated via videolaryngoscopy and laryngeal electromyography (LEMG). Larynges from euthanized animals were analyzed via immunofluorescent staining for the presence of reinnervation.


RESULTS
One animal that received phenol and 3 animals that received high-dose VNC died of toxicity-related complications. In the surviving neurotoxin-treated animals, videolaryngoscopy showed increased lateralization of the immobile vocal fold. Only 1 phenol-injected rat had adductor complex motor recruitment (score of 3+) with LEMG. The other neurotoxin-treated animals demonstrated an absence of adductor complex reinnervation, with only insertional activity and fibrillations (no motor units/recruitment). Spontaneous ipsilateral abductor reinnervation was not affected by the adductor injections.


CONCLUSIONS
Low-dose VNC injections appear to be relatively safe and effective in selectively inhibiting spontaneous aberrant reinnervation after RLN injury in an animal model.
McRae
Bryan R
BR
Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, Indianapolis 46202, USA.
Kincaid
John C
JC
Illing
Elisa A
EA
Hiatt
Kelly K
KK
Hawkins
Jan F
JF
Halum
Stacey L
SL
D000818:Animals; D004576:Electromyography; D007821:Laryngeal Muscles / Q000294:innervation; D007828:Laryngoscopy; D008297:Male; D009416:Nerve Regeneration / Q000187:drug effects; D019800:Phenol / Q000627:therapeutic use*; D051381:Rats; D061226:Recurrent Laryngeal Nerve Injuries; D012597:Sclerosing Solutions / Q000627:therapeutic use*; D046608:Synkinesis / Q000517:prevention & control*; D050257:Tubulin Modulators / Q000627:therapeutic use*; D014750:Vincristine / Q000627:therapeutic use*; D014827:Vocal Cords / Q000503:physiopathology
D012597:Sclerosing Solutions; D050257:Tubulin Modulators; D019800:Phenol; D014750:Vincristine