A novel model for examining recovery of phonation after vocal nerve damage.
OBJECTIVE
Recurrent laryngeal nerve injury remains a dominant clinical issue in laryngology. To date, no animal model of laryngeal reinnervation has offered an outcome measure that can reflect the degree of recovery based on vocal function. We present an avian model system for studying recovery of learned vocalizations after nerve injury.


METHODS
Prospective animal study.


METHODS
Digital recordings of bird song were made from 11 adult male zebra finches; nine birds underwent bilateral crushing of the nerve supplying the vocal organ, and two birds underwent sham surgery. Songs from all the birds were then recorded regularly and analyzed based on temporal and spectral characteristics using computer software. Indices were calculated to indicate the degree of similarity between preoperative and postoperative song.


RESULTS
Nerve crush caused audible differences in song quality and significant drops (P<0.05) in measured spectral and, to a lesser degree, temporal indices. Spectral indices recovered significantly (mean=43.0%; standard deviation [SD]=40.7; P<0.02), and there was an insignificant trend toward recovery of temporal index (mean=28.0%; SD=41.4; P=0.0771). In five of the nine (56%) birds, there was a greater than 50% recovery of spectral indices within a 4-week period. Two birds exhibited substantially less recovery of spectral indices and two birds had a persistent decline in spectral indices. Recovery of temporal index was highly variable as well, ranging from persistent further declines of 45.1% to recovery of 87%. Neither sham bird exhibited significant (P>0.05) differences in song after nerve crush.


CONCLUSIONS
The songbird model system allows functional analysis of learned vocalization after surgical damage to vocal nerves.
Bhama
Prabhat K
PK
Department of Otolaryngology-Head & Neck Surgery, University of Washington School of Medicine, Seattle, Washington, USA. pbhama@gmail.com
Hillel
Allen D
AD
Merati
Albert L
AL
Perkel
David J
DJ
D000818:Animals; D020209:Cranial Nerve Injuries / Q000209:etiology / Q000503:physiopathology*; D004195:Disease Models, Animal; D046369:Finches; D007858:Learning; D008297:Male; D010699:Phonation; D011446:Prospective Studies; D020127:Recovery of Function; D012009:Recurrent Laryngeal Nerve / Q000503:physiopathology*; D061226:Recurrent Laryngeal Nerve Injuries; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013239:Stereotyped Behavior; D013997:Time Factors; D014828:Vocalization, Animal