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and denervation duration using multivariate logistic

regression analysis method in a large series of 349

UVFP patients who underwent delayed laryngeal rein-

nervation. We also performed further stratification anal-

ysis aimed at one of the identified significant variables—

denervation duration—in order to investigate the effect

of denervation duration on the surgical outcome of

laryngeal reinnervation.

MATERIALS AND METHODS

Patient Characteristics

Our study was approved by the institutional review board

of Second Military Medical University, Shanghai, People’s

Republic of China. The medical records of 349 UVFP patients

(94 males and 255 females; mean age 44.0 years, ranging 17–69

years) who underwent anastomosis of the main branch of the

ansa cervicalis to the RLN between January 1996 and January

2011, and who were followed for at least 2 years, were reviewed.

The etiology of UVFP in this series of patients was RLN injury

during thyroid surgery. Informed consent was obtained from all

patients involved in this study. Patients who were lost to follow-

up were excluded. There was a minimum waiting period of 6

months following onset of RLN injury to allow for possible spon-

taneous recovery or compensation. The median denervation

course was 16.1 months (range, 6–45 months). When stratified

by denervation duration, the number of patients in each dener-

vation duration group was: 172 (49.3%) patients with a dener-

vation duration 6 to 12 months (group A); 108 (30.9%) patients

with a denervation duration 12 to 24 months (group B), and 69

(19.8%) patients with a denervation duration

24 months

(group C). The median follow-up period after laryngeal reinner-

vation was 70.8 months (range, 24–156 months).

Surgical Procedure

The surgical procedure has been elaborated in our previ-

ous report.

Briefly, under general anesthesia, the ipsilateral

ansa cervicalis was explored, and the main branch was trans-

ected at the bifurcation and freely mobilized for preparation of

anastomosis. The RLN was dissected at a point sufficiently far

from the injury site to provide a tension-free anastomosis and

then transected. Under an operating microscope, the distal

RLN stump was anastomosed to the main branch of the ansa

cervicalis using nylon 11-0 thread in three to five epineural

sutures.

Videostroboscopy

All patients were observed via a videostroboscope (RICH-

ARD WOLF GmbH, model 5570, Knittlingen, Germany) during

“eee” phonation at a comfortable loudness and pitch for as long

as possible, and dynamic videos were recorded preoperatively

and postoperatively. Three experienced laryngologists who had

not performed any of the surgeries reviewed all of the videos.

The videos were randomized, and the reviewers were blinded to

whether the videos were preoperative or postoperative. Visual

laryngeal analysis included glottal closure (0, complete; 1,

slightly incomplete; 2, moderately incomplete; 3, severely

incomplete), vocal fold position, vocal fold edge of paralyzed

side, phrase symmetry, and regularity. Consensus of the

reviewers was reached on the visual appearance of the larynx.

Our previous studies demonstrated that the above parameters

were consistent in presenting reinnervation outcome of vocal

fold paralysis, among which the parameter glottal closure was

the most representative one

; therefore, only the parameter

“glottal closure” was included when performing statistical anal-

ysis using a univariable analysis and multivariable logistic

regression analysis.

Vocal Function Assessment

Vocal function assessment included perceptual evaluation,

acoustic analysis, and maximum phonation time (MPT) mea-

surement. Preoperative and postoperative voice samples con-

taining sustained vowels /a/ and connected speech samples were

used for perceptual evaluation and acoustic analysis. The

recording equipment consisted of a digital audiotape recorder

and a dynamic microphone (Tiger Electronics Inc., North Read-

ing, MA). Five laryngologists who had been trained in grade,

roughness, breathiness, asthenia, and strain (GRBAS) rating

performed voice perceptual evaluation using a perceptual rating

scale (GRBAS) for voice quality and characteristics. The ratings

were accomplished in a blinded fashion, with patient voice sam-

ples arranged in a random manner. Each listener was asked to

score connected speech samples for overall grade, roughness,

breathiness, asthenia, and strain using a voice-quality scale for

each parameter (0, normal; 1, mild; 2, moderate; 3, severe). The

values were averaged among the five listeners. Our previous

studies demonstrated that the interrater and intrarater reliabil-

ity was acceptable (interrater reliability

0.76; intrarater

reliability

0.81).

4,9

In addition, the above five parameters of

perceptual evaluation were consistent in presenting vocal out-

come of vocal fold paralysis, among which the parameter overall

grade was the most representative one.

Therefore, only the

parameter “overall grade” was included when performing statis-

tical analysis using a univariable analysis and multivariable

logistic regression analysis.

The acoustic parameters of sustained vowel /a/ were eval-

uated using Praat software (Boersma, Paul & Weenink, David

(2011). Praat: doing phonetics by computer [Computer pro-

gram]. Version 5.1.12, retrieved from

http://www.praat.org/

The acoustic parameters were mean noise-to-harmonics ratio

(NHR) and measures of phonatory stability—jitter (local) and

shimmer (local). MPT was defined as the duration of sustained

phonation of the vowel /a/ after maximum inspiration and was

measured preoperatively and postoperatively.

Laryngeal Electromyography

A four-channel electromyograph and concentric needle

electrodes (Dantec Counterpoint, Copenhagen, Denmark) were

used for the laryngeal electromyography (EMG) recordings. To

test for proper needle position, the unaffected vocal fold was

examined first. The electromyographic activity of the bilateral

thyroarytenoid (TA) muscles was recorded during the following

two stages: while breathing quietly when relaxed, and while

pronouncing the vowel /eee/ with the greatest exertion, then

sniff. One board-certified otolaryngologist performed the EMG,

and a neurologist operated the EMG machine and interpreted

the EMG results. The neurologist rated the VMUR using the

following scale: 0, full interference; 1, mixed interference; 2,

simple interference; and 3, without motor unit potential.

Statistical Analysis

The perceptual evaluation, acoustic analysis, and MPT

data did not follow normal distribution and were presented as

median (low quartile, upper quartile). We sought to evaluate

influencing factors for the surgical outcome of laryngeal rein-

nervation using multivariable logistic regression methods.

Potential influencing factors were examined in univariable

Laryngoscope 124: August 2014

Li et al.: Denervated Duration on Reinnervation for UVFP