Transoral Approach to Laser Thyroarytenoid Myoneurectomy for Treatment of Adductor Spasmodic Dysphonia: Short-Term Results

Chih-Ying Su. MD: Hui-Ching Chuang. MD; Shang-Shyue Tsai. PhD: Jeng-FenChiu,PhD

Objectives: The surgical technique for the resection of the recurrent larvngeal nerve for adductor spasmodic dysphonia (ASD) ha.s high late failure rates. During the pa.st decade, botulinum toxin has emerged as the treatment of choice for ASD. Although effective, it also has significant disadvantages, including a temporary effect and an unpredictable dose- response relationship. In this study we investigated the effectiveness of a new transoral approach to laser thyroarytenoid mynneurectomy for treatment of ASD. Methods: Fourteen patients with ASD underwent transoral laser myoneurectomy of bilateral thyroarytenoid muscles. Under general anesthesia, an operating miLTOscope and a carbon dioxide laser were used to pertorm myectomy of the mid-posterior belly of bilateral thyroarytenoid muscles together with neurectomy ofthe terminal nerve fibers among the deep muscle bundles. Care was taken not to damage ihe vocal is ligaments, arytenoid cartilages, and lateral cricoarytenoid muscles. Preoperative and postoperative videolaryngostroboscopy and vocal assessments were studied, Results: The 13 patients who completed more than 6 months follow-up were enrolled in this study. Moderate and marked vocal improvement was achieved in 92^;? of the patient.s (12 of 13) after laser surgery during an average tbllow-up period of !7 months (range. 6 to 31 months). No vocaifoldatrophy or paralysis was observed in any patient. None of the patients had a recurrence during the foilow-up period. I Conclusions: Transoral laser myoneurectomy of bilateral thyroarytenoid muscles is a relatively simple, effective, and valuable technique for the treatment ot ASD. The durability ot outcome achieved with this procedure is encouraging. Key Words: adductor spasmodic dysphonia, recurrent laryngeal nerve, thyroarytenoid muscle, transoral laser myoneurectomy. ventricular fold hypertunction.

INTRODUCTION ynx. However, its exact cause remains unknown.

Spasmodic dysphonia most often presents as Adductor spasmodic dysphonia tends to be resis- the adductor type. Adductor spasmodic dysphonia tant to voice therapy. Surgical procedures that have (ASD) is a focal form of adult-onset taryngeal dys- been used to treat this disorder include recurrent tonia. and is related to excessive adduction or ad- laryngeal nerve section and type II thyroplasty.^'^ ductor spasm ofthe vocal folds.' It is characterized However, the.se procedures have the disadvantages by a strain-strangled voice pattern that is husky, of- of high late failure rates and a tendency to leave the ten with tretnors and involuntary pitch breaks in patient with a persistent breathy voice.-^-''Therefore, voicing. The voice quality often deteriorates further botulinum toxin (Botox) chemodenervation remains during stressful speaking situations. This can have a the standard of care for ASD in most tertiary spe- negative impact on the patient's quality of life and cialty centers.' Botox injection in the thyroarytenoid may lead to social isolation. As a type of dystonia. muscles provides substantial though variable relief spasmodic dysphonia has been considered a chron- of symptoms with few or no side effects. Howev- ic tieurologic disorder of central motor processing er, the vocal improvement lasts for a limited time, causing action-itiduced muscular spasms of the lar- from several v^'eeks to several months, and then the

From the Department of Otolaryngology and the Voice Center. Chang Gung Memorial Hospital. Kaohsiung Medical Center. Chang Giing Universily College of Medicine (Su. Chuang). the Department of Health Care Adniinistralion. I-Shou Universily (Tsai). and [he Department of Medical Technology. Foo Yin Insiitnle of Technology (Chiu). Kaohsiung. Taiwan. Supported in part by grants from the National Science Council. Taiwan (NSC94-2314-B-182-05.1). and Chang Gung Memorial Hospital (NMRPDI40711). " Presented in part ai the XVIII IFOS World Congress. Rome. Italy. June 25-30. 2^)5. Correspondence: Chih-Ying Su. MD. Dept of Otolaryngology. Chang Gung Memorial Hospital. No. 123. Ta-Pei Rd. Niao-Sung Hsiang, Kao.<;hiung Hsien.Taiwan.

II 12 Su el al. Liser Myoneurectomy for Spasmodic Dysphonia

Fig 1. Inlraopenilive endoscopie \ icws uf (ransoni! kiser thyroarylenoid mynneurectumy. A) Endolaryiigciil apixMritnce prior to operation. B) Laser partial resection of left ventricular fold to expo.se whole line v(Kal fold. C) Reseclion of mid- posterior belly of left thyroarytenoid muscle. D) Completion of bilateral thyroar>'tenoid myoneurectomy. effect gradually subsides. Despite efforts to refine stitutional Review Board) included 14 consecutive both surgical and Botox treatments, symptom re- patients who had the presumptive diagnosis of ASD lief in ASD with tremor remains suboptimal.^' None when referred. Informed consent was obtained from of the available interventions at the nerve and end all patients before surgery. Detailed history-taking organ offer a definitive cure. As the outcome after and physical examinations were performed before all of these procedures is less than optimal, new ap- operation, including subjective and objective vocal proaches to the treatment of ASD that may offer a function assessments and videolaryngostroboscopy. long-term solution need to be developed. Surgical Procedure. All 14 patients underwent The ideal treatment for ASD would improve both transoral laser partial resection of the ventricular sound production and voice quality without interfer- folds, followed by myoneurectomy of bilateral thy- ence with the sphincter function of the glottis, and roarytenoid muscles. Under general anesthesia, a would provide long-lasting benefit. In an attempt to direct laryngoscope was inserted to expose the true achieve this goal, we designed a transoral approach vocal folds and ventricular folds (Fig IA). An op- to laser partial resection of ventricular folds fol- erating microscope and a carbon dioxide laser (10 lowed by myoneurectomy of bilateral thyroaryte- W, continuous mode, and slightly defocused) were noid muscles. This procedure has not been fully ad- used to perform partial resection of the ventricular dressed in the literature. fold to expose the entire true vocal fold (Fig IB). PATIENTS AND METHODS Then the middle and posterior thirds of bilateral thy- Clinical Data. This study (approved by our In- roarytenoid muscles were vaporized or resected (Fig Su el al. La.ser Myoncurcctoiny for Spasmodic Dxsphonhi 13

Fig 2. A) Diagrani demonslrates ihiit left veiuricular fold ;itid middle belly of thyroarytenoid muscle are partially resecled by laser. Terminal fibers of recurrent laryngeal nerve among muscle bundles are also vaporized. B) Terminal neurovascular bundle (arrow) among deep muscle bundles was visualized during laser surgery. Laser vaporization of nerve fibers usually elicited strong twitching of muscle. IC.D). Care was taken not to damage the vocalis Laboratory (core model CSL4300B. KayPENTAX, ligaments, arytenoid cartilages, or lateral cricoary- Lincoln Park, New Jersey). The aerodynamic pa- tenoid muscles {Figs ID and 2A). During laser sur- rameters of mean airflow rate and maximal phona- gery on the deep muscle bundles, terminal nerve fi- tion time were measured with the circumferential- bers were frequently found among the musele bun- ly vented pncumotachograph mask and differential dles. The nerve fibers, if any. were vaporized as well transducers of the Aerophone system (Aerophone 11. (Fig 2B. arrow). Laser vaporization of the nerve fi- model 6800. KayPENTAX). bers usually elicited a strong twitching of the muscles. In some cases, bleeding from the small vessels Perceptual assessments were determined by con- occurred, which could be readily stopped by cauter- sensus of a speech pathologi.st and a senior laryngol- ization. Fibrin glue or suture material was not ap- ogist who listened to the recorded speech samples. plied to the surgical wound in any patient. The pro- Judgments of voice quality and ability to commu- cedure was usually accomplished within 1 hour. Tbe nicate were made on the basis of overall grade (G). patients were requested to maintain voice rest for roughness (R), breathiness (B). interruption or break several days to 1 week after the operation. (I), .strain (S). and tremor (T). Clinical severity before and after surgery was evaluated with a 3-point Vocal Function Studies. Vocal function studies ordinal scale on which "()"" indicated normal. "1" and videolaryngostroboscopy were performed as mild dysfunction. "2" moderate dysfunction. "3" previously described.^""^ The patients were assessed severe dysfunction, and "4" profound dysfunction. 1 or 2 weeks after operation and again approximate- Clinical subjective judgment of the improvement of ly 1.3.6. 12. 18, and 24 months after operation. All voice quality and communication after surgery was data were prospectively recorded in a database, in- assessed by a patient self-rating scale. The findings cluding associated symptoms, surgical procedures, were classified into categories of normal, markedly complications, vocal function test results, and surgi- improved, moderately improved, slightly improved, cal outcomes. The vocal assessments involved per- not changed, and worse. ceptual judgment of voice quality, acoustic analysis, and aerodynamic measurements. AM of the assess- Laryngostroboscopy was performed with a Kay- ments occurred a minimum of 6 months after op- PENTAX Stroboscopy Unit (model 8100). Video eration. and audio data were loaded onto the computer disk (RLS 9100B. KayPENTAX) to facilitate duplicate Acoustic and aerodynamic parameters were ap- evaluation by 2 judges experienced in laryngostro- plied to recordings of each subject producing sus- boscopy. The mucosal wave patterns, wave ampli- tained vowel productions in a soundproof room. tude, periodicity, glottal and supraglottal closures, Acoustic variables including mean fundamental fre- and presence of tremors during phonation were as- quency, noise-to-harmonics ratio, jitter, and shimmer sessed. Each parameter of specific laryngeal move- were measured by use of a Computerized Speech ment disturbance was rated on a 5-point scale, with 14 Su et al. Laser Myoneurectomy for Spasmodic Dysphonia

TABLE I. SUMMARY OF FOURTEEN PATIENTS WITH ADDUCTOR SPASMODIC DYSPHONIA Voice Ventricular Aryienoid A-P Glottal Grade* Tremor* Strain* Hypcrfiinction* Overadduction* Compres.sitm* Postop Case Age Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Preop Postop Follow- No.

0 as normal appearance and 3 as the most severe Yideolaryngostroboscopic Findings. Before op- dysfunction. eration, the most frequent abnormal laryngostro- boscopic findings of the 13 patients were mucosal Statistical analysis used the SPSS for Windows waves with aperiodic and rigid vibration patterns, package {SPSS Inc. Chicago. Illinois). Simple de- excessive arytenoid adduction, ventricular fold hy- scriptive statistics (means and .standard deviations) perfunction, anterior-posterior compression of the were calculated for each variable. Statistical analy- glottis, and tremors with phonation (Table 1). The ses used the paired /-test and the Wilcoxon signed dysfunctions and their patterns varied greatly. After rank test for paired measurement of ordinal vari- operation, the abnormalities of the parameters were ables. improved in 12 patients, but unchanged in 1. None ofthe patients developed significant vocal fold atro- RESULTS phy, bowing, or paralysis after laser surgery. Post- operative assessment of the vibratory patterns of From September 2003 through February 2006, a each vocal fold revealed a significant trend toward total of 14 patients with ASD underwent transoral increased vibration waves. laser myoneurectomy of bilateral thyroarytenoid muscles. One ofthe 14 patients was excluded from Perceptual Assessment and Subjective Ratings. the study because she was followed up for less than The patients perceived an overall voice improve- 6 months. The data of 13 patients are summarized ment after surgery (Tables I and 2). The assess- in Table I. There were 2 men and 11 women. Their ment was nonparametric. because it was based on ages ranged between 33 and 69 years, with a mean the ranks of the observations. The nonparametric age of 51 years. The average duration of dysphonia test that is analogous to the paired /-test is the Wil- was 41 months (6 months to 13 years). The post- coxon signed rank test. There was a significant de- operative follow-up ranged from 6 to 31 months crease (improvement) in the scales of grade, rough- (mean, 17 months). ness, strain, interruption or break, and tremor after operation (p < .05). but no significant change in the In the early postoperative period, the laryngeal scale of breathiness. Self-ratings and independent mucosa had an edematous and injected appearance. ratings of the outcome of the surgery indicated that The patients usually had hoarseness and slight as- marked and moderate improvement was obtained in piration. As the acute inflammatory reactions re- 92% of the patients (12 of 13). There was no recur- solved, the aspiration and voice quality greatly im- rence noted during follow-up ranging from 6 to 31 proved within I to 4 weeks after operation. Within months. One patient (case 12) who had no symp- 3 months after surgery, the voice began to reach its tomatic improvement al^er surgery took Artane. an best quality. antiparkinsonism drug prescribed by a neurologist Su et al. Laser Myoneurectomy for Spasmodic Dysphonia 15

TABLE 2. COMPARISON OF PREOPERATIVE AND reduces the effect of adductor spasms on voice pro- POSTOPERATIVE PERCEPTUAL ASSESSMENTS duction. In an animal study by Genack et al,'' an ex- No. of Two Related P ternal approach to partial unilateral thyroarytenoid Parameters Patients Samples Test Z (2-Tailed} myectomy through a thyroplasty cartilage window Grade 14 El postop/preop -3.27 .001* was used to as.sess the surgical effects on larytigeal 14 E2 postop/preop -2.85 .004* function. They found that thyroarytenoid muscle ac- Roughness 14 El postop/preop -3.27 .001* tion potential atnplitudes were reduced on the side 14 E2 postop/preop -2.23 .026* of the myectomy. Histologically, the excised muscle Breathiness 14 El postop/preop -1.73 .083 was replaced with fibroareolar tissue without evi- 14 E2 postop/preop -1.41 .157 dence of muscle regeneration. However, preserva- Strain 14 El postop/preop -2.99 .003* tion of glottal competence with good true vocal fold 14 E2 postop/preop -2.7! .007* adduction was observed. In a retrospective, unblind- Tremor 14 El postop/preop -2.95 .003* ed study by Koufman et al,'-^ an external approach 14 E2 postop/preop -3.08 .002* to myectomies ofthe thyroarytenoid and lateral cri- Interruption or 14 El postop/preop -2.97 .003* coarytenoid muscles was performed on 5 ASD pa- break 14 E2 postop/preop -2.89 .004* tients. (One ofthe procedures was performed endo- *Statistically significant at p < .05 {Wilcoxon signed rank lesi). scopically.) Their preliminary results showed improved voice fluency in all patients. By using a di- in another hospital. She obtained symptom relief rect laryngoscope and a carbon dioxide laser, Dedo during medication. Unfortunately, a deterioration of and Izdebski'^ perfortned a vocal fold thinning pro- vocal symptoms was noted when she ceased taking cedure to release the recurrent spasticity after a uni- the medicine because of the side effect of general lateral section of the recurrent laryngeal nerve. In weakness. 1990, Woo'"* described a new thyroplasty approach to laser-assisted thyroarytenoid myectomy; in recent Acoustic and Aerodynamic Analyses. The results literature, partial immobility of one vocal fold was of acoustic and aerodynamic analyses are summa- also obtained by transoral radiofrequency coagula- rized in Table 3. There was a statistically significant tion. Similar to the above techniques, the transoral decrement (improvement) in the mean jitter and laser myoneurectotny procedure used in this study maximal phonation time from the preoperative to also intervenes on the end organ (ventricular folds, the postoperative performance (p < .05). No signifi- thyroarytenoid muscles, terminal nerve fibers, and cant differences were noted on paratneters of mean neuromuscular junctions; Figs 1 and 2). After la- fundamental frequency, shimmer, noise-to-harmon- ser vaporization, the wound over the thyroarytenoid ics ratio, or mean airflow rate. muscle heals and is replaced with fibrous or fibroareolar tissue. This is postulated to result in a sig- DISCUSSION nificant decrease in the numbers of ihe thyroarytenoid muscle fibers and the motor unit end plates af- Most ASD patients suffer from uncontrolled vo- ter laser surgery. To create an effect similar to that cal spasms during phonation. The spasms produce of the external myectomy method, laser myoneurec- a constrained voice quality with intermittent breaks tomy is also designed to weaken the contraction of or interruptions of voicing.' In addition, the voice the thyroarytenoid muscle and thereby reduce the pattern may also be tremulous. Botox chemodener- excessive adduction and spasm of the vocal folds vation weakens neuromuscular contraction by inter- (Fig 3). Because muscle regeneration is not evident fering with release of acetylcholine at the motor end after myectomy, a long-lasting benefit of laser myo- plates (neuromuscular junctions), resulting in a tem- neurectomy on symptom relief of ASD is expected. porary paresis or paralysis of the vocal folds.**' This

TABLE 3. COMPARISON OF PREOPERATIVE AND POSTOPERATIVE MEASURES OF ACOUSTIC AND AERODYNAMIC PARAMETERS No. of Preoperative Postoperative Parameters Patients (Mean±SD) (Mean ± SD) Fundatnental frequency (Hz) 14 197.51 ± 33.82 194.85 ±42.16 0.22 .830 Maximum phonation time (s) 14 I4.14± 8.49 18.79 ± 7.49 -2.39 .033* Jitter (%) 14 2.69 ± 1.89 1.33± 1.03 2.40 .032* Shimmer (dB) 14 033 ± 0.42 0.45 ± 0.40 0.54 .595 Noise-to-harmonics ratio 14 0.26 ± 0.23 O.I7± 0.12 1.46 .168 Mean airflow rate (Us) 14 0.05 ± 0.05 0.08 ± 0.14 -0.81 .434 •^Statistically significant at p < .0.5. 16 Su et al. iMser Myoneurcclnmy for Spasmodic Dysphonia

Fig 3. (Case 3) Endoscopic view of larynx in 61 -year-uld Icmale patient with adductor spasmodic dysphonia before (A. inhalation; B, phonation) and after (C, inhalation; D, phonation) laser thyroarytenoid myoneurectomy. Hyperadduction of false and true vocal folds and anterior-posterior glottal compression were markedly improved after laser surgery.

During a mean of 17 months (range, 6 to 31 months) able. The recurrent laryngeal nerve tertninates in of foi lovv-up, there was no evidence of recurrence of the thyroarytenoid muscle. The terminal branching vocal symptoms in this series. Compared to Botox pattern is that of the anatomic neural networks sur- chemodenervation and external surgical methods, rounding the muscle fascicles and within the muscle the iransoral laser technique has the advantages of (Fig 2). In the thyroarytenoid muscles, the.se neural time- and cost-effectiveness with low morbidity. It networks become dense and complicated, especial- is a relatively simple and effective procedure with a ly in the medial part of the thyroarytenoid (voca- durable outcotne. lis muscle) at the vocal fold margin.'"^ An immuno- histochemical study of human true vocal folds by There are two main issues of concern in per- Sheppert et al"^* revealed that the most neuromus- forming laser myoneurectomy of the thyroaryte- cular junctions (74%) were located in the middle noid muscle: 1) determination of the most appropri- third ofthe thyroarytenoid muscle, followed by the ate location and volume ofthe muscle vaporized or posterior third, and the least (7%) were found in the resected; and 2) assessment of whether significant anterior third. Rossi and Cortesina'^ also reported vocal fold atrophy, vocal fold paralysis, or glottal that approximately 70% to 80% of the fibers in the incompetence will occur after laser surgery. From medial two thirds of the thyroarytenoid muscle had an anatomic and neurophysiological perspective, multiple motor end plates. These findings suggest the design of the transoral approach to laser vapor- that the tnedial thyroarytenoid has a much ftner neu- ization focusing on the tniddle and posterior thirds ral control that probably offers an increased rate of ofthe thyroarytenoid muscle is feasible and reason- rise of tension in vocalization." Because neuromus- Sti et al. Laser Myoneurectomy for Spasmodic Dysphonia 17 cular junctions are most highly concentrated within treatment for the correction of ventricular fold hy- the mid-posterior belly of the muscle, laser surgery perfunction and anterior-posterior glottal compres- on ASD patients should be targeted to this region sion in voicing (Table 1 and Fig 3). (Figs I and 2). After laser resection of a significant amount of muscle tissue just lateral to the vocal lig- Because mild endolaryngeal edema and tem- ament, fibrous or scar contracture created in heal- porary laryngea! dysfunction is an inevitable con- ing may serve lo pull the free edge of the vocal fold sequence of laser surgery, transient aspiration and away from the midline. and thereby eliminate the ex- hoarseness were noted in mosi of our patients. The cessive adduction of the vocal folds in voicing. La- symptoms and signs gradually subsided, and the pa- ser vaporization extending to the anterior portion of tients* voice quality stabilized within 1 to 3 months the thyroarytenoid muscle is not recommended, be- after surgery. cause it offers little further benefit on control of vocal spasms and may also increase the risk of anteri- The postoperative complications were minimal in or glottal incompetence after surgery. We advocated this series. One of our patients developed hemopty- the use of laser myoneurectomy on bilateral thyroar- sis immediately after the operation. Revision laryn- ytenoid muscles. It is assumed that laser weakening gomicroscopy revealed a small bleeder at the right of a unilateral vocal fold may result in abnormally ventricular wound, which was successfully stopped asymmetric vibrations of the vocal folds. Although by cauterization. Four of the 13 patients developed most patients had had various degrees of temporary granulomas at the wound site in the ventricular area. aspiration and husky voice during the initial postop- All of the granulomas gradually disappeared within erative period, none of them developed significant 3 to 4 months of operation. vocal fold atrophy (bowing) or glottal incompetence Moderate to marked improvement in speech fol- during follow-up. The absence of postoperative vo- lowing laser thyroarytenoid myoneurectomy was cal fold paralysis in this series may be attributed to reported by 92% of patients (12 of 13) in this se- the routine preservation of the lateral cricoarytenoid ries. Eight of them obtained a near-normal to nor- muscle during the procedure (Fig 2B). mal voice quality after operation. Our results dem- onstrated that this new transoral approach to laser Patients with ASD often exhibit glottal and ven- thyroarytenoid myoneurectomy for the treatment of tricular fold (false vocal fold) hyperadduction orhy- ASD effectively improved both perceptual assess- perfunction. The ventricular folds are composed of ment and subjective ratings of voice production. elastic connective tissue containing fat cells and a The patients' voice quality and glottal configura- few muscular fibers derived from the vocaiis mus- tion achieved a stable and persistent status at 6 to 31 cle of the corresponding side. A substantial number months after surgery. of motor end plates are scattered in the ventricular fold.'^ On the basis of the hypothesis that a "ventricular muscle" may contribute to the hyperfunc- CONCLUSIONS tion in these cases, Schonweiler et al'** treated 8 Transoral laser myoneurectomy of bilateral thy- ASD patients with bilateral injection of botulinum roarytenoid muscles is a relatively safe, effective, toxin type A into the ventricular folds. They found and technically simple surgical procedure for treat- that ventricular fold hypertunction had resolved in ment of ASD. It results in a sustained weakening but all patients at 4 weeks after treatment. In the cur- adequate functioning of tlie thyroarytenoid muscles. rent series, partial laser resection of the ventricular This technique has excellent potential to provide an fold (Figs I and 2) was also shown to be an effective alternative for management of ASD patients.

Ackno>^ ledgmcnts: The authors thank Ben-Hua Wang and Wei-Han Su for prtKluction of the Figures. Wei-Wei Su for contribuling to this project, and Chu-An Cheng for perlbrining ihe vocal function tests and voice assessments. :

REFERENCES 1. Blitzer A. Brin MF, Stewart CF. BotLilinuni toxin man- enilization thyroplasty for adductor spasmodic dysphonia. Ann agement of spasmodic dysphonia (laryngeiil dyslonia): a 12- Otol Rhinol Laryngol 201)0:109:1S7-93. year experience In more than 900 patients. Laryngoscope 5. Chan SW. Baxter M. Oates J. Yorston .A. Long-lenm re- I998;1()8;I435-4I. sults of type II thyropiasty for adduclor spasmodic dysphonia. 2. Dedo HH. Recutrenl larvngeal nerve section for spastic Laryngoscope 2004; 114:1604-8. dysphonia, Ann Otol Rhinol Laryngol 1976;8ri:4.'il-y. 6. Sulica L. Contemporary management of spasmodic dys- 3. Aronson AE. De Santo LW. Adduction spastic dyspho- phonia. Ciirr Opin Oloiaryngol Head Neck Surg 2()O4:i2:.'S43- nia: three years after recurrent laryngeal nerve resection. Laryn- 8. goscope 1983;93;l-8. 7. Su CY. Lui CC. Lin HC, Chiu JF, Cheng CA. A new 4. Isshiki N.Tsuji DH. Yamamoto Y. lizuka Y. Midline lat- paramedian approach to arytenoid adduction and strap muscle 18 Su et al. ixLser Myoneurectomy for Spasmodic Dysphonia

transposition for vocal fold medialization. Laryngoscope 2002; tion) treatment of spastic dysphonia. Laryngoscope !983;93: 112:342-50. 268-71. 8. Su CY.TsaiSS.Chiu JF. Cheng CA. Medialization laryn- 14. Woo P. Carbon dioxide laser-assisted thyroarytenoid my- goplasty with strap muscle transposition for vocal fold atrophy omectomy. Lasers Surg Med 1990:10:438-43. with or without sulcus vocalis. Laryngoscope 2004;! 14:1106- 12. 15. Sanders L Wu BL, Mu L, Li Y. Bilier HF. The tnnervation of the human larynx. Arch Otolaryngol Head Neck Surg 9. Su CY.Tsai SS. Chuang HC. Chiu JF. Functional signifi- 1993;119:934-9. cance of arytenoid adduction with the suture attaching to cricoid cartilage versus to thyroid cartilage for unilateral paralytic dys- 16. Rossi G.Cortesina G. Morphological study of the laryn- phonia. Larj'ngoscope 2005; 115:1752-9. geal muscles in man. Insertions and courses of the muscle fi- 10, Sheppert AD.SpirouGA.Berrebi AS.GitrnettJD.Three- bres, motor end-plates and proprloceptors, Acta Oiolaryngol dimensional reconstruction of imniunolabeled neuroniuscular (Stockh) 1965;59:575-92. junctions in the human thyroarytenoid muscle. Laryngoscope 17. Bendiksen FS. Dahl HA, Teig E. tnnervation pattern of 2003:113:1973-6. different types of muscle fibres in the human thyroarytenoid IL Genack SH.WooP.Coilon RH.Goyette D. Partial thyro- muscle. Acta Otolaryngoi (Stockh) 1981:91:391-7, arytenoid myectomy: an animal study investigating a proposed 18. Rosen M, Malmgren LT, Gacek RR. Three-dimensional new treatment for adductor spasmtxlic dysphonia. Otolaryngol computer reconstruction of the distribution of neuromuscular Head Neck Surg 1993;108:256-64. junctions in the thyroarytenoid muscle. Ann Otol Rhlnol Laryn- 12. Koufman JA. Rees CJ. Halum SL. Blalock D.Treatment go! 1983:92:424-9. of adductor-type spasmtjdic dysphonia by surgical myectomy: 19. Schonweiler R, Wohlfarth K, Dengler R, Ptok M. Su- a preliminary report. Ann Otol Rhinol Laryngol 2(K)6;115:97- praglottal injection of botulinum toxin type A in adductor type 102, spasmodic dysphonia with both intrinsic and extrinsic hyper- 13. Dedo HH. lzdebski K. Problems with surgical (RLN sec- function. L^aryngoscope 1998:108:55-63.