声帯筋を含む甲状被裂筋における横断面の100ポイントから求めた単位面積1mm²あたりの筋線維数は, 男女25例 (♂14, ♀11) の平均値で639.8±48.6であった.収縮機能が異なる筋線維型の比率の平均値は, 緊張性収縮と持久力を有するタイプIの赤筋線維が43.7%で最も高かった.次いでタイプIとIIの両形質を示すタイプIIIの中間筋線維が28.8%, 速動性と瞬発力を発揮するタイプIIの白筋線維が27.6%となり, タイプIの赤筋線維の割合は有意に高かった.また筋線維型の性差を比較すると女性ではタイプIIIの中間筋線維が, わずかに高いのに対し, 男性ではタイプIの赤筋線維とタイプIIの白筋線維が高かったが, それぞれ有意差はみられなかった.また甲状被裂筋と前脛骨筋との比較では, 甲状被裂筋の赤筋線維が有意に高かった.以上の結果よりヒトの発声に関与している声帯筋を含む甲状被裂筋はタイプI型の赤筋線維の比率が多い筋であることが示された.

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Adductor spasmodic dysphonia is a vocal disorder of uncertain etiology. Section of recurrent laryngeal nerve or injection of botulinum toxin has been used as an effective treatment. But they are not satisfactory long-term treatments. Bilateral thyroaritenoid muscle myectomy is performed by microlaryngoscopic method to four patients of adductor spasmodic dysphonia. Good speech results are obtained immediately after the operation, and no side effect is observed. No patient has experienced a return of symptoms, after one-year follow-up. Bilateral thyroaritenoid myectomy may be a hopeful new long-term approach to spasmodic dysphonia treatment.

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Injection laryngoplasty is a reliable surgical procedure to correct laryngeal incompetence caused by vocal fold paralysis. Although autologous fat has become a popular injection material in recent times, there are numerous problems that need to be addressed in its application in laryngoplasty; such as, injection site of the vocal fold, quantity of injection material, possibility of improvement for glottal gap, and resorption of injected autologous fat. The purpose of this study is to investigate the problems of autologous fat injection in laryngoplasty.
The clinical study involved 31 patients with unilateral vocal fold paralysis who had received treatment at the Kurume University Hospital between 2000 and 2003. The pathological study was comprised of 23 patients whose autologous fat harvested by liposuction was utilized as injection material during laryngoplasties between 2000 and 2005.
In patients with a small degree of vocal fold bowing, autologous fat was injected locally into the thyroarytenoid muscle lateral to the oblong fovea of the arytenoid cartilage. As a result, the glottal gap decreased and postoperative voice functions, maximum phonation time (MPT) and mean airflow rate during phonation over comfortable duration (MFRc) improved. In patients with a large degree of vocal fold bowing, the autologous fat was injected not only into the thyroarytenoid muscle lateral to the ob-long fovea of the arytenoid cartilage but also into the thyroarytenoid muscle at the membranous portion of the vocal fold. As a result, the glottal gap decreased and postoperative voice functions, MPT and MFRc improved.
The fat cell membranes had not been damaged during liposuction harvesting or microinjection by our technique. The diameters of fat cells ranged from 41.3±8-117.1±15.2μm. A few patients with large diameter fat cells showed less improvement compared to those with smaller diameters for the postoperative voice functions, MPT, MFRc, and pitch perturbation quotient (PPQ).
These results indicate that fat injection into the thyroarytenoid muscle lateral to the oblong fovea of the arytenoid cartilage produced good postoperative voice function and this procedure can improve a large degree of glottal gap. Resorption of autologous fat may be related to not only the size and density of fat cells but also their proliferation.

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After denervation of the recurrent laryngeal nerve (RLN), the innervated laryngeal muscles are atrophied. We have reported that functional electrical stimulation (FES) delivered to the thyroarytenoid (TA) muscle prevents muscle atrophy after denervation. The reason why FES prevents atrophy of the muscle is not yet clear.
In this study, we tried investigating a hypothesis that the superior laryngeal nerve (SLN) might have a role in preventing muscle atrophy by FES. We used 23 adult rats in this study. Resections of the left SLN with the left RLN, or bilateral SLNs with the left RLN were performed. A pair of thin wire stimulation electrodes (50 u m) was placed in the left TA muscle. The animals were divided into two groups : a stimulated group and a non-stimulated group. In the stimulated group, FES, with 2 mA rectangular pulses of 0.2 ms duration at 2 Hz lasting for 1 hour, was delivered to the TA muscle once every 2 days. After the stimulation periods of 2 or 4 weeks, frontal sections of the larynx 8 pm in thickness were prepared. The differences in the area of the TA muscle, the area of the TA muscle fiber and the density of the TA muscle fiber were compared between the denervated (left) side and the non-denervated (right) side.
Atrophy of the TA muscle was observed in spite of the ipsilateral and/or bilateral denervation of the SLN. The effect of FES to prevent muscle atrophy was also observed regardless of SLN resection. The results obtained from this study suggested that the information to the central nervous system through the SLN was not indispensable for preventing muscle atrophy after denervation of RLN.

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フォルマリン注入屍(男•女各2例)から得られたヒト喉頭筋について,筋腹横断面の筋線維数および筋線維の太さを検討し,四肢およびその他の筋と比較してその特徴を明らかにした。組織標本はセロイジン包埋,H•E 染色標本によった。ヒト喉頭筋については,筋の大きさは筋腹横断面積および筋線維数から見て非常に小さい部類に入ったが,筋線維の太さは最小1.000μ2で,咬筋,舌骨筋群,手の大部分の筋より大であり,太い方の喉頭蓋筋とでは抗重力筋に匹敵した。すなわち,喉頭筋は一般に小さいが,筋線維は大であり,筋線維構成は各例間の個体差が著しく,性別的傾向は見られなかった。これらの中で,声帯の緊張と弛緩に関する輪状甲状筋とでは筋線維総数においては個体差が著しく,発声の個人差との関係が考えられた。

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We had previously demonstrated that an immediate nerve-muscle pedicle (NMP) transplantation to denervated thyroarytenoid (TA) muscle was effective in the recovery from atrophic changes due to successful reinnervation in rats. However, in a clinical situation, we usually treat patients suffering from persistent unilateral vocal fold paralysis. The objective of this study was to examine the effects of NMP transplantation on long-term denervated TA muscle in rats.
Ten Wistar rats were divided into two groups; animals treated with left recurrent laryngeal nerve (RLN) transection alone (DNV group) and animals treated with NMP method at 16 weeks after RLN transection (NMP group). Both groups were euthanatized at 26 weeks after RLN transection. We evaluated the status of the neuromuscular junction (NMJ) and the muscle area histologically.
In the NMJ, the ratio of the number of nerve terminals to that of acetylcholine receptors in the NMP group was significantly higher than that in the DNV group (p<0.01). With reference to the muscle areas, the ratios of the treated side to the normal side of the entire muscle and that of the individual muscle fibers in the NMP group were significantly higher than those in the Denervated group (p<0.01, p<0.05, respectively).
Our study supported that up to 16 weeks after denervation, successful reinnervation can be established in denervated TA muscle by the NMP method.

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The present study evaluated the clinical application of functional electrical stimulation (FES) to restore the laryngeal function in patients with vocal fold paralysis.

Canines were used in this study. We designed an electrode array consisted of 8 active platinum disk electrodes, mounted on a 10 × 8 × 1 mm silicone plate. This electrode array was placed between the thyroid cartilage and thyroarytenoid muscle. The vocal fold angle from the anterior commissure to the vocal process was measured endoscopically in the anesthetized animal. To clarify the influence of FES on reinnervation, the animals were divided into reinnervated and denervated groups. In the reinnervated group, the right recurrent laryngeal nerve was sectioned and repaired immediately. In the denervated group, the right recurrent laryngeal nerve was sectioned and not repaired.

In the reinnervated group, FES induced optimal glottal closure with a low current. The vocal fold easily adducted to the midline. Even in the denervated group, FES was able to induce vocal fold adduction. However, the induced adduction was very small, and a high current was required to move the vocal fold. The vocal fold gradually moved from the medial to the lateral side over 3 minutes of continuous stimulation, but adduction of the paralyzed vocal fold have sustained and positioned over the midline for 2 minutes.

This study showed that paralyzed adductor muscle stimulation with new shaped electrodes was able to induce optimal glottal closure. Vocal fold adduction by FES was assumed to be sufficient to improve the voice sounds in cases of unilateral vocal fold paralysis.

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The purpose of this study is to analyse the effect of recurrent laryngeal nerve denervation on postnatal developement of intrinsic laryngeal muscle fibers. The composition of muscle fiber types in the medial component of thyroarytenoid muscle (m-TA), the lateral component of thyroarytenoid muscle (1-TA) and the posterior cricoarytenoid muscle (PCA) has been compared between normal and denervated rats using myosin ATPase stain method.
With denervated rats, Type 1 fibers disappear rapidly after denervation. Type 2A fibers do not appear through the observed period. On the other hand, the developmental changes of Type 2B fibers are almost similar to those of normal rats. The denervation prevents the differentiation of Type 1 and 2A fibers, but almost does not change the differentiation of Type 2B fibers.
These results suggest that the recurrent laryngeal nerve has an important role at its specified course of postnatal differentiation of intrinsic laryngeal muscle fibers.

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Bilateral thyroarytenoid myectomies were performed on 14 patients with adductor spasmodic dysphonia. During the operation bleeding was controlled by use of a Laser. Fat tissue was removed from abdomen and inserted into vocal fold to fill in the defect after myectomy procedures and to prevent scarring. The patients' voices were restored to normal without recurrence of dysphonia. This operation is one of the most effective treatment for adductor spasmodic dysphonia.

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A rare case of adductor spasmodic dysphonia treated with a botulinum toxin injection after a bilateral thyroarytenoid myectomy is reported. We discuss the difficulty of diagnosis and therapy of spasmodic dysphonia. The patient was a 60 year-old male, whose profession depended on his voice. He had felt dysphonia over 20 year period. He had tried voice therapies and folk remedies at otolaryngological and psychopathological hospitals; however, the symptom had not improved. Later he read an article regarding spasmodic disphonia in a newspaper and subsequently visited Osaka University Hospital. He was then diagnosed with adductor spasmodic dysphonia. A bilateral thyroarytenoid myectomy was performed in March of 2001. After the operation, the dysphonia had improved and he was able to spend dairy life with better vocalization. Although it initially appered that there would be no recurrence, he gradually came to sense dysphonia slightly. This dysphonia however was to a degree that couldn't be objectively recognizeed. He hoped this symptom could be remedied because of his occupation as a Buddhist priest and singer of Japanese court music. Boturinum toxin injection therapy was recommended to him. After this treatment, the symptom improved. He presently continues this therapy.

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Six adult cats weighing 2.2kg-4.7kg were anesthetized with intramusclar injection of ketamine hydrochloride. The left recurrent laryngeal nerve (RLN) was transsected at the level of the second tracheal ring and both cut ends were ligated. Electrically induced vocalization was performed after Kanai's method. (Horsley-Clarke coordinates AP : 0, L4.5-5.5, H-3.0--6.0) (stimulation 0.2ms, 50-100 μA, lasting 5-10s) Then EMG of the throarytenoid muscle (TA) and the posterior cricoarytenoid muscle (PCA) were recorded. Besides, single afferent discharges from laryngeal sensory receptors of paralyzed vocal cord were recorded during evoked vocalizations.
In this study, 25 weeks after transection of RLN the EMG of left TA showed recruitment, but the electromyographical activity of the left PCA was not observed. 20 weeks after neurorraphy of the left RLN and the left Ansa cervicalis, the activity of the left TA was almost the same as that of the control side. The EMG of left PCA showed the continuous activity during vocalization. However, in all cases, no return of vocal cord mobility was observed. The rate of single afferent discharge from laryngeal sensory receptors on paralyzed side was corresponded to fundamental frequency change during evoked vocalization. This result suggests that the central nervous system has received informations about paralyzed vocal cord vibrations from larynx during evoked vocalization.

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Improvement of breathy dysphonia due to unilateral vocal fold paralysis (UVFP) is usually achieved by implementing various kinds of phonosurgical procedures, including intracordal injection, type I thyroplasty, arytenoid adduction (AA), and combinations thereof. However, some patients do not recover their “normal” voices after surgery. Normal voices can be attained by providing the immobile vocal fold with the median location and symmetrical bulk and tension of the unaffected vocal fold. Because phonosurgical procedures offer “static” adjustment of these features, the thyroarytenoid muscle (TA) does not work as the body of the immobile vocal fold, resulting in little contribution to voice production and tuning. The authors refined the technique of nerve-muscle pedicle (NMP) flap implantation onto the TA muscle and have applied this innovative method, together with AA, in the treatment of breathy dysphonia due to UVFP since July 2002. Ninety-six patients had undergone NMP flap transfer and AA as of July 2016. The operative procedures are described in detail. Long-term follow-up over 2 years in 47 patients revealed significant improvement in the phonatory function after surgery. Furthermore, most parameters showed significant improvement during the follow-up period.

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The injection of botulinum toxin into the thyroarytenoid muscle (BT injection) is the standard therapy used around the world in the treatment of adductor-type spasmodic dysphonia (ADSD) ; however, in Japan BT injection is not approved at all institutions. Thyroarytenoid muscle myectomy-Muta method (TAM) and type 2 thyroplasty (TP2) are the main surgical procedures currently undertaken for treatment of ADSD. The choice between the two procedures is difficult.We reviewed the operative methods of surgical treatment of ADSD. The voice was evaluated preoperatively and postoperatively using the Mora method. The spasmodic ratios (%) were calculated based on the Mora score and then compared. Both operative methods yielded satisfactory results in terms of treatment outcome and satisfaction level of the patients. In surgical therapy for ADSD, TAM and TP2 yield approximately equivalent treatment outcomes. When selecting between the two operative methods, the merits and demerits of each method for each individual patient should be considered.

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We reported previously that when the internal branch of the superior laryngeal nerve (ISLN) of generally anesthetized cats was electrically stimulated, short latency response (early response, ER) and long latency response (late response, LR) emerged in the thyroarytenoid muscle (TA). Vibratory stimulation, applied to the contralateral subglottic mucosa as a conditioning stimulation, enhanced LR, particularly in phase I (the transitional phase from inspiration to expiration). When the vibratory frequency was elevated from 100 Hz to 350 Hz at 50 Hz interval in phase I, vibration effect was observed in all frequencies investigated. Maximum effect was obtained at 300 Hz. Following denervation of ISLN, the vibration effect was minimized, and it did not depend on the vibratory frequency.
In the present study, the data processing technique was partly modified : the sampling time of integrated EMG of LR was shortened. As a result, LR was occasionally divided into two responses L₁R and L₂R. The effect of vibratory stimulation on the subglottic mucosa differed for L₁R and L₂R.
The effect of subglottic vibration upon LR as a function of vibratory frequency may reflect frequency characteristics of the mechanoreceptors to vibration in the subglottic mucosa. If this is the case, the aforementioned results indicate that there are two groups of mechanoreceptors having different frequency characteristics against vibration. The mechanoreceptors in the laryngeal mucosa play an important part in auto monitoring systems of vibration.

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