An ultrastructural study of the neuromuscular junctions of the cat intrinsic laryngeal muscles. II. Synapse formation by autonomic nerves

The purpose of this study is to identify the origin of the nerve terminals of unknown origin observed at the previously denervated neuromuscular junctions in the cat intrinsic laryngeal muscles. The results were as follows: 1. Until 3 weeks after the transection of the recurrent laryngeal nerve, no nerve terminals were found at the neuromuscular junctions of the intrinsic laryngeal muscles except for the cricothyroid muscle, and no nerve fibres were detected in the Schwann tubes formed by Schwann cells and perineural cells. In addition, autonomic nerves around the vessels in the muscles were markedly decreased. 2. At 6 weeks, accompanied by an increase of autonomic nerves around the vessels, nerve fibres and nerve varicosities containing a number of large granular vesicles were observed in the Schwann tubes. 3. From 9 to 30 weeks, nerve terminals containing large granular vesicles were found at the neuromuscular junctions in all cases, even though the superior laryngeal nerve or the vagal nerve was transected on the ipsilateral side. 4. A spontaneous discharge was recognized in 6/8 cases after 6 weeks, but an evoked electromyogram could not be recognized. 5. The synaptic vesicles of the nerve terminals were labelled by 5-hydroxydopamine (5-OHDA), which was used as a marker for the sympathetic nerve. From these results, it was indicated that if the transected recurrent laryngeal nerve was prevented from regenerating, the autonomic nerves around the vessels entered into the Schwann tubes and reached the denervated neuromuscular junctions, instead of the motor nerve. The effect of autonomic nerves on muscle fibres was discussed.     

Regeneration of the laryngeal sensory nerves

A study of reflex movements of the vocal cords induced by electrical stimulation of the mucous membrane of the larynx or by stimulating the internal branch of the superior laryngeal nerve (evoked EMG) in normal dogs was done. The internal branch was sectioned subsequently, and the progress of regeneration was studied over a period of months by the same techniques. Return of reflex movement to the vocal cords and soft palate indicated that the nerve was completely regenerated between 60 and 75 days, and reinnervation of the mucous membrane was accomplished by 79 days. The evoked EMG induced by stimulation of the nerve showed abnormal threshold and wave form. Secretion of the laryngeal mucous membrane glands never returned during stimulation. These observations are discussed in relation to surgery of this area.     

Afferent activity in the external branch of the superior laryngeal and recurrent laryngeal nerves.

We investigated the presence of respiratory-modulated receptors in the recurrent laryngeal nerve (RLN) and the external branch of the superior laryngeal nerve (ExtSLN) in anesthetized, spontaneously breathing dogs. Of 39 receptors recorded from the ExtSLN, the vast majority responded with a slowly adapting discharge to compression of the cricothyroid muscle, and only 1 responded to probing of the laryngeal mucosa. Ten receptors showed a respiratory modulation. All 30 receptors recorded from the RLN responded to probing of the laryngeal lumen, most of them (60%) with a rapidly adapting response. Seven of the slowly adapting receptors exhibited a respiratory modulation; 38% of the receptors tested were stimulated by water, and only 15% by smoke. No receptors stimulated by laryngeal cooling were identified in either nerve. Our study indicates that in the RLN and the ExtSLN there are relatively few afferents responding to changes in transmural pressure and mechanical irritation, as compared to the internal branch of the SLN. The relative scarcity of receptors responding to transmural pressure and irritant stimuli is consistent with previous observations in dogs that indicate a preponderant role for afferents in the internal branch of the SLN in the reflex responses to laryngeal stimulation.     

Functional laryngeal abduction following reimplantation of the recurrent laryngeal nerves

Functional reinnervation was established in a patient following complete laryngo-tracheal separation with avulsion of both recurrent laryngeal nerves. Following reattachment of the larynx to the trachea, the severed stumps of the recurrent laryngeal nerves were implanted into the laryngeal abductors (the posterior crico-arytenoid muscles). One year later the patient had good abduction and adduction of her vocal cords. The abduction is thought to be a result of reinnervation by the recurrent laryngeal nerves, the adduction due to the action of crico-thyroid muscle whose innervation was undisturbed by the original injury.     

An epidemiological study of laryngeal cancer in Japan.

This report presents the findings of an epidemiological study of laryngeal cancer in Japan, based on 6,360 cases treated and registered during the 10-year period from 1960 through 1969. The number of the patients increased 1.5 times from 1960 to 1969. Geographically the absolute number of recorded cases was proportional to the population density; in other words, it was larger in heavily urbanized areas and smaller in rural regions. An anatomical classification revealed that the incidence of supraglottic and glottic cancer was about equal (3,121 and 3,176 cases), and subglottic cancer was only 1 percent of the total. Histologically, 98.6 percent were of the squamous cell carcinoma and 1.4 percent were of the basal cell carcinoma, adenocarcinoma, transitional cell carcinoma, etc. As to the age and sex distribution, the majority of the patients were 50 to 70 years old, and those in their 60's were most numerous. The ratio between men and women was 9.6 to 1. 56.1 percent of the patients surveyed were found to have a blood relation with a history of cancer and 31 percent were engaged in occupations where they used their voices frequently. Smoking habits were found in 96 percent of the patients surveyed and as many as 52 percent came under category of heavy smokers. Cigarette smoking might be regarded as a significant factor in laryngeal cancer, while alcohol consumption was not as significant a causal factor as smoking. The living environment had no explicit relationship to laryngeal cancer in the above-mentioned period of years.     

Morphometry of the recurrent laryngeal nerves of the rat

In mammals the recurrent laryngeal nerves are dissimilar in length between both sides. This asymmetry involves different time of arrival of the stimulus to the laryngeal musculature controlled by each nerve. Thus, several explanations have been addressed to elucidate the closest of the glottis at the same time despite the unlike length of the nerves. However, previous works on the topic lack of several important data. The present study compares, in two groups of 10 and 6 rats, the length and the composition of myelinated fibers in the recurrent laryngeal nerves of both sides, by means of light microscopy and a computerized morphometric analysis. The results show a mean difference of 0,84 cm longer the left than the right recurrent laryngeal nerve. No statistical differences were observed in the number of myelinated fibers between both sides. However, the myelinated fibers of the right side were statistically bigger in diameter than the fibers of the left side. The data are discussed in the context of the mechanisms for the compensation of the dissimilar length of both recurrent laryngeal nerves.     

Juvenile laryngeal papillomatosis. An epidemiological study from the Copenhagen region

All 23 patients treated for juvenile laryngeal papillomatosis (JLP) in the Copenhagen region during a 4-year-period were identified for this epidemiological study. The incidence of JLP was 0.6/100,000 among the population at risk, children aged 0-14 years, and the prevalence was 0.8/100,000. It is concluded that the condition in most cases has a good prognosis, i.e., short duration and low morbidity. Only in a few cases JLP will take a long-lasting course. Regression before or during puberty does not in all cases ensure complete recovery. Thus, 7 of 12 adult patients experienced a quiescent period of 21 years (median). Spread of papillomas to the bronchogenic system seems to be a serious prognostic sign.     

耳内镜下实验解剖内耳门区血管神经

目的利用不同角度耳内镜对内耳门区的血管、神经进行解剖观测,为临床开展桥脑小脑角区微创外科手术提供解剖学依据。方法10%甲醛固定的成人头颅标本(正常完整颅底)15例(30侧,性别不限),模拟迷路后进路操作,分别以0°、30°、70°耳内镜对内耳门区的血管、神经进行解剖观测、分析。结果①内耳门区动脉袢出现率为70%(21/30),而且大部分需借助30°或70°内镜方能明确;②前庭耳蜗神经裂隙界面在内耳门区出现率为60%(18/30),其中12侧此裂隙界面位于内耳道外、Ⅷ脑神经束的外表面,用0°内镜即可直接看到;另外6侧此裂隙界面位于内耳道内、Ⅷ脑神经束的下表面,只有用30°或70°的内镜才能看到,与Ⅷ脑神经束进入内耳道前所形成之前庭耳蜗神经裂隙界面恰成90°旋转。结论应用多角度耳内镜才能清晰观察并确认内耳门区的动脉袢及定位前庭耳蜗神经裂隙界面。     

Systematization and histomorphometry of human laryngeal nerves

Laryngeal nerves were dissected from 100 fresh subjects in order to compare right and left superior and inferior laryngeal nerves. The origin and the distribution of the vascularization was studied. The structure of these nerves was precised through an histomorphometric approach (distribution number of myelinated fibers per mm2, diameter of myelinated fibers). A cartographic study of the laryngeal nerves confirmed the structure of this innervation. The main conclusion of this study is the importance of the plexis structure of the laryngeal innervation and the variations of the nerve fibers diameter as a function of the length of the fiber.     

The superior laryngeal nerve and the interarytenoid muscle in humans: an anatomical study

The course and distribution of the rami perforantes of the superior laryngeal nerve was studied in 12 human larynges. Dissections utilized a Zeiss operating microscope. All branches were found to perforate the muscle; none terminated in the muscle. This eliminates anatomically any possibility of motor supply to the mterarytenoid muscle from the superior laryngeal nerve. The rami perforantes also contribute to mucosal innervation on the posterior surface of the larynx. Histologic studies of whole fetal larynges corroborated the findings from the dissections. No evidence of innervation across the midline was found. No extra-laryngeal division of the recurrent laryngeal nerve into abductor and adductor branches was found. A ganglion around the superior laryngeal nerve was described.     

Microvascular anastomoses. An evaluation of laser-assisted technique

The carbon dioxide milliwatt laser was used to perform microvascular anastomoses in 23 rat femoral arteries and 21 femoral veins. This technique was compared with conventionally sutured controls and then evaluated histologically at intervals of three to four days and 1, 2, 3, 4, 6, 8, and 12 weeks postoperatively. Patency rates in both methods, for arteries and veins, were comparable, confirming the feasibility of laser-assisted microvascular anastomoses. Moreover, the major benefit of the laser procedure was to allow for fewer sutures, thereby diminishing a foreign body reaction.     

Anastomosis between the two facial nerves.

A case of traumatic facial palsy incurred during the removal of an acoustic neuroma via a sub-occipital craniectomy is presented. The palsy was rehabilitated to a satisfactory degree by anastomosing the normal to the paralyzed facial nerve using an autoplastic peripheral nerve graft of suitable length to join the two.