HSC Section 6 Nov2016 Green Book

the most representative one 4 ; therefore, only the parameter “glottal closure” was included when performing statistical anal- ysis using a univariable analysis and multivariable logistic regression analysis.

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.

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. 4 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. 4 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. 4 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

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. 4 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

Laryngoscope 124: August 2014

Li et al.: Denervated Duration on Reinnervation for UVFP

6