Takahiko Yamagata

Causes of recurrent laryngeal nerve paralysis

OBJECTIVE Persistent hoarseness due to recurrent laryngeal nerve paralysis (RLNP) reduces the quality of life unless it is adequately treated. This study examined the indications for phonosurgical intervention in patients with RLNP. MATERIALS AND METHODS The medical records of the Ehime University Hospital, Ehime, Japan, from October 1976 until December 1997 were reviewed retrospectively to identify patients with RLNP. The data collected included age, gender, paralyzed side, and cause of paralysis. RESULTS Four hundred and sixty-six patients with RLNP were identified: 262 males and 204 females. Unilateral RLNP was present in 422 patients, while 44 presented with bilateral RLNP. The incidence was relatively high in the 7th and 8th decades, and was twice as high in male patients as in female patients. The 466 patients were divided into 2 groups: Group 1 included 225 patients seen before January 1987, and Group 2 included 241 patients seen after this date. The number of patients with postoperative RLNP was significantly higher in Group 2 (124 of 239 patients) than in Group 1 (65 of 227 patients) (P<0.05). Surgery for cardiovascular disease, esophageal cancer, and skull base and thyroid gland tumors contributed to this increased incidence of postoperative RLNP. CONCLUSIONS Patients with persistent unilateral RLNP require appropriate treatment for hoarseness, regardless of its cause. Since the incidence of RLNP related to surgery was significantly increased in Group 2, phonosurgery has become more important for improving the quality of life of these patients.

Restoring Vocal Fold Movement after Transection and Immediate Suturing of the Recurrent Laryngeal Nerve with Local Application of Basic Fibroblast Growth Factor: An Experimental Study in the Rat†

Objective: To evaluate the effects of basic fibro‐blast growth factor (bFGF) on the recovery of vocal fold movement and the attenuation of laryngeal muscle atrophy after transection of the recurrent laryngeal nerve (RLN).

Age-Related Remodeling of the Hypopharyngeal Constrictor Muscle and Its Subneural Apparatuses: A Scanning Electron Microscopical Study in Rats

Age-related remodeling of the hypopharyngeal constrictor muscle was studied by comparing the morphological features of the subneural apparatus (SNA) of the thyropharyngeal (TP) and cricopha ryngeal (CP) muscles in young and old rats. Scanning electron microscopy revealed that the TP and CP muscles had both gutter- and depression-type SNAs, although different proportions of the two types of apparatus were found in each muscle. In young-adult rats, the gutter-type SNA was predominant in the TP muscle, whereas in the CP muscle the depression type was predominant. By contrast, in old rats, the depression-type SNA was predominant in the TP muscle, while no such transformation of the dominant SNA was noted in the CP muscle. In addition, the number of type IIb and type I muscle fibers was lower and greater, respectively, in older animals compared with those of younger animals. Furthermore, there were more type IIc fibers in the TP muscle of old rats, but no difference in the CP muscle between young and old animals. These findings suggest that the transformation of SNAs and the muscle fibers of the hypopharyngeal constrictor muscle takes place during aging and that their remodeling processes differ in the TP and CP muscles.

Scanning Electron Microscopic Study of the Neuromuscular Junctions of the Cricothyroid and Thyroarytenoid Muscles in Rats

Neuromuscular junctions were observed in the cricothyroid (CT) and thyroarytenoid (TA) muscles of adult rats by scanning electron microscopy after removing the intramuscular connective tissue components using the HCI hydrolysis method. Morphologically, the junctions were classified into three types in the CT muscle and two types in the TA muscle, based on the structural characteristics of the subneural apparatuses, including junctional folds. In the CT muscle, type 1 junctions (32%) consisted of more than 15 cup-like depressions with slit-like junctional folds. Type 2 junctions (20%) were characterized by approximately 10 cup-like depressions with a small number of pit- or slit-like junctional folds. Type 3 junctions (48%) had irregular labyrinthine gutters with slit-like junctional folds. In the TA muscle, type 1 (82%) and 2 (18%) junctions had similar structures to type 1 and 2 junctions in the CT muscle, respectively. Histochemical studies using myosin adenosine triphosphatase staining showed that both CT and TA muscles predominantly consisted of type II muscle fibers (78% and 82%, respectively), and that the diameter of type II fibers was larger than that of type I fibers. These findings suggest that the type 2 junction belongs to type I muscle fibers, while both type 1 and type 3 junctions belong to type II fibers, and that the type 3 junction is a structural variation of the type 1 junction. The significance of the structural differences of the subneural apparatuses in the intrinsic laryngeal muscles is discussed briefly.Neuromuscular junctions were observed in the cricothyroid (CT) and thyroarytenoid (TA) muscles of adult rats by scanning electron microscopy after removing the intramuscular connective tissue components using the HCl hydrolysis method. Morphologically, the junctions were classified into three types in the CT muscle and two types in the TA muscle, based on the structural characteristics of the subneural apparatuses, including junctional folds. In the CT muscle, type 1 junctions (32%) consisted of more than 15 cup-like depressions with slit-like junctional folds. Type 2 junctions (20%) were characterized by approximately 10 cup-like depressions with a small number of pit- or slit-like junctional folds. Type 3 junctions (48%) had irregular labyrinthine gutters with slit-like junctional folds. In the TA muscle, type 1 (82%) and 2 (18%) junctions had similar structures to type 1 and 2 junctions in the CT muscle, respectively. Histochemical studies using myosin adenosine triphosphatase staining showed that both CT and TA muscles predominantly consisted of type II muscle fibers (78% and 82%, respectively), and that the diameter of type II fibers was larger than that of type I fibers. These findings suggest that the type 2 junction belongs to type I muscle fibers, while both type 1 and type 3 junctions belong to type II fibers, and that the type 3 junction is a structural variation of the type 1 junction. The significance of the structural differences of the subneural apparatuses in the intrinsic laryngeal muscles is discussed briefly.

Postnatal changes in the types of muscle fibre in the canine inferior pharyngeal constrictor

Deglutition is considered to be immature in infants and to mature postnatally. We evaluated postnatal changes in muscle fibre type composition in the canine inferior pharyngeal constrictor muscle, which consists of the thyropharyngeal (TP) and cricopharyngeal (CP) muscles, using ATPase staining with respect to the maturation of deglutition. In the TP muscle type IIA and type IIB fibres, the main components in the adult, were already predominant at 1 week postnatally. The percentage of primitive type IIC fibre showed a rapid reduction and reached the adult level within 6 weeks. In the CP muscle, the majority of fibres were type IIC at 2 weeks. At 2 months, more than 20% of the fibres were still type IIC and the proportion of type I fibres as a main component in the adult was smaller than that of the adult. None of the puppies younger than 9 weeks old had a fibre type composition similar to that of the adult. In the extensor digitorum longus and flexor digitorum superficialis, the compositions of muscle fibre types became similar to that of the adult at 6 and 9 weeks of age, respectively. Thus, the TP muscle matured more rapidly than the limb muscles, while the CP muscle matured more slowly. We speculated that the TP and CP muscles have specific individual differentiation patterns associated with their functional roles before and after birth, compared with the limb muscles.

A complex muscle fiber network in the cricothyroid muscle: a scanning electron microscopic study.

Objectives: To examine the three‐dimensional ultrastructure of cricothyroid (CT) muscle fibers to elucidate their morphologic characteristics with regard to the specific functions of the muscle.

Scanning electron microscopic study of the muscle fiber arrangement in the rat cricopharyngeal muscle.

Conclusions. Myomyous junctions comprise a complex muscle fiber network, which is thought to synchronize the activity of the cricopharyngeal (CP) muscle fibers. Myomyous and myotendinous junctions explain the heterogeneity in muscle fiber length which contributes to the efficient behavior of the muscle. This scanning electron microscopy (SEM) study demonstrated the complex muscle fiber arrangement of the CP muscle and improved on the previous description of its morphological specificity. Objective. To examine the 3D ultrastructure of the inferior pharyngeal constrictor muscle fibers to obtain further knowledge of their morphological characteristics with regard to the specific functions of the muscle in deglutition. Material and methods. Six adult rats were used. Their CP and thyropharyngeal (TP) muscles were obtained and processed using the HCl hydrolysis method to remove i.m. connective tissue. The fine muscle fiber structure was observed by means of SEM. Results. Multifaceted muscle fiber interconnections (myomyous junctions) were identified in the CP muscle. The myomyous junctions were characterized by the tight connection of many finger-like processes at the ends of a lateral branch or bifurcating trunk of the muscle fibers. In addition, muscle fibers occasionally tapered and ended within the muscle belly, forming myotendinous junctions. The TP muscle lacked these structures.

Ganglion cells in the posterior cricoarytenoid muscle of the rat following experimental denervation.

Objective —To investigate morphological changes of the i.m. ganglion cells in the posterior cricoarytenoid (PCA) muscle of the rat following denervation of the recurrent laryngeal nerve. Material and Methods —The recurrent laryngeal nerve on the left side of the rat was resected. Three weeks after transection, the PCA muscle was removed for morphological study using light and electron microscopy. Results —No morphological changes were found in the i.m. ganglion cells in the PCA muscle, even though the myelinated nerve fibers were destroyed and had disappeared in ramified i.m. bundles. Around the cell body, numerous non-myelinated nerve fibers were found; these contained a large number of clear, spherical synaptic vesicles ≈50 nm in diameter and several dense-cored vesicles ≈100 nm in diameter. In contrast, neuromuscular junctions in most muscle fibers with partially disoriented and/or disintegrated myofibrils showed degenerative figures. In some instances, however, multiple nerve terminals were detected in contact with the postsynaptic membrane. Like the varicose swellings of non-myelinated nerve fibers around the ganglion cell body, these nerve terminals contained, in addition to clear synaptic vesicles (50 nm in diameter), several dense-cored vesicles (100 nm in diameter). Conclusion —We suggest that i.m. ganglion cells in the rat PCA muscle may supply postganglionic nerve fibers to the denervated neuromuscular junctions after transection of the nerve.

Laryngeal Paralysis in Children

Masamitsu Hyodo, Takahiko Yamagata, Kazumi Motoyoshi and Aki Taguchi Recurrent laryngeal nerve paralysis in children is a relatively rare disease. Its clinical features in children are considered dissimilar to those in adults. Here we present 11 cases of children with recurrent laryngeal nerve paralysis and discuss the manner of treatment for this disease. Clinical features compared and found to differ with those in adults are summarized as follows: 1) congenital paralysis is the most common cause, 2) bilateral paralysis is frequent, 3) congenital systemic abnormalities are frequently combined, 4) respiratory disorder is the most critical symptom especially in infants, 5) vocal cord movement ordinarily recovers in a few years especially in patients with congenital paralysis. Management strategies should be focused on the maintenance of a safe and stable airway and the acquisition of intelligible speech. Less traumatic laterofixation of the vocal cord by Ejnells procedure is a preferable surgical treatment for prolonged respiratory disorder due to bilateral laryngeal paralysis.

Neurotrophic factors on regeneration of denervated recurrent laryngeal nerve

motion and MHC composition characteristic of denervation were observed in all animals, despite evidence of reinnervation by EMG. Following joint fixation, alteration in MHC composition consistent with denervation was observed only at 30 days, as seen in the nerve crush model. Conclusion: Temporary injury and vocal fold immobilization result in transient shifts in MHC composition. Nerve transection and repairs and subsequent reinnervation result in persistent alteration of MHC composition and vocal fold dysfunction. Clinical Significance: These findings suggest that expression of normal MHC composition is dependent on the condition of appropriate neural contact and functional reinnervation. In subsequent studies, MHC composition will be used as a biological marker to evaluate future strategies for the management of laryngeal paralysis. (Supported by NIDCD grant K08DC0081.)