The muscular tissue of the vestibular folds of the larynx

The muscular tissue of the vestibular folds was investigated in plastinated serial sections of 32 normal adult larynges. Three muscular systems could be distinguished. A posterolateral muscle layer was found to be developed at the lateral margin of the posterior part of the vestibular fold. Its fibers extended in a sagittal direction, and their contraction probably resulted in an adduction of the entire tissue of the vestibular fold towards the midline. Within the anterior part of the vestibular fold, an anterolateral muscle sheet was seen to attach to the thyroid cartilage. An anteromedial muscular system consisted of scattered groups of muscle fibers situated medially and dorsally to the laryngeal ventricle and saccule. These fibers were presumed to exert a downward pressure on the vestibular folds, in addition to an adductor function. According to clinical experience, adductor movements of the vestibular folds can be trained, even in cases with a recurrent laryngeal nerve lesion, in order to produce a compensatory voice. Thus, the muscles of the vestibular folds are probably innervated by the superior laryngeal nerve.

Visualization of the human larynx: a three-dimensional computer modeling tool

The larynx is a complex compact organ. A detailed understanding of the anatomical relationships of its various structures is critical to the various workers in the field. To facilitate this goal, a 3-D model of the human larynx has been developed using multiple thin section MRI and CT images taken through a cadaver larynx. A databank of individual laryngeal structures ('units') has been built up. A software package has then been utilized which allows for representation of any of the stored 'units'. In this manner, elements of the larynx can be viewed from any direction, with the larynx static or in motion. Similarities and differences from current CD-ROM packages of the larynx are discussed.

Management of the N(0) neck

Paramount among the challenges and controversies among the head and neck surgeon is the proper treatment of the N0 neck. Therapeutic intervention for the N0 neck usually involves any of two treatment modalities alone or in combination: surgery or radiation therapy. This article discusses the potential treatment strategies for possible subclinical neck metastasis and the rationale for their use on a site by site basis for head and neck primary tumors.

Magnetic resonance imaging of the normal canine larynx

The purpose of this study was to define the normal anatomic structures in the canine larynx with magnetic resonance images. TI-weighted images were taken in the sagittal and transverse planes. The MR images were obtained comparing MR images to dissection planes. Magnetic resonance imaging provides excellent anatomic detail of laryngeal structures. Therefore, it is of value of diagnostic imaging of some respiratory diseases in the dog.

[Subepithelial glands in the hamster's larynx]

We have performed, with light microscope, a study about the distribution and morphology of the subepithelial glands of the hamster's larynx. The results are: at the base of the tongue the great deal of the glands are mucous, at the epiglottic base seromucous and at the subglottic space (at the level of cricoid cartilage) serous.

Use of a lighted stylet for intubation via the laryngeal mask airway

PURPOSE

To assess a new technique for intubation via the laryngeal mask airway (LMA) in which a lighted stylet is used to optimise the position of the LMA before intubation.

METHODS

In 114 patients, following LMA insertion, the lighted stylet (Trachlight Wand) with mounted tracheal tube (TT) was advanced 1.5 cm beyond the mask aperture bars and the anterior neck observed for a distinct central point of light at the cricothyroid membrane (CTM). If this was not seen, the LMA was repositioned in the pharynx, depending on the location of the light, by manually advancing, withdrawing or rotating the device, manipulating the head/neck or trying an alternative size. Tracheal intubation was attempted only when transillumination was correct. The TT with lighted stylet was advanced until the supra-sternal notch was transilluminated.

RESULTS

In 89 patients (78%) the CTM was transilluminated without repositioning, in 12 (10%) a single positional adjustment was required, and in 10 (9%) a change of LMA size was required. In three patients (3%) transillumination of the CTM was impossible. In the 97% of patients in whom transillumination was correct, tracheal intubation was successful in all at the first attempt without the need for further repositioning or size change.

CONCLUSION

The lighted stylet is useful in facilitating intubation via the LMA in anaesthetised adult patients when used as a guide to optimal LMA position.

[Physiology of the larynx]

The larynx consists of the cartilaginous-osseous framework, elastic membranes and ligaments, joints, muscles, nerves, vessels, and interior cavity. The laryngeal functions are the protection of the airway during swallowing, respiration (i.e. maintainance of the airway) and phonation. During the pharyngeal phase of swallowing the swallow reflex induces a laryngeal closure in three levels and a superior-anterior movement of the larynx and hyoid bone. The laryngeal airway is maintained by the circumference of the cricoid cartilage. Phonation is the phylogenetically recent function of the larynx and was made possible by the laryngeal descent. The sound production is explained according to the myoelastic-aerodynamic theory. The diagnostics of laryngeal diseases is performed in close cooperation between otorhinolaryngology and radiology. For diagnostic purposes, the physiology of the larynx requires to take into account not only morphological, but also functional aspects.

Larynx

The complex anatomy of the larynx, best conceptualized as a set of mucosal folds draped over a cartilaginous skeleton, has developed as a consequence of its many upper airway functions. Despite its deep location in the neck, much of the mucosal surface of the larynx is amenable to direct laryngoscopic inspection. The role of the radiologist in laryngeal imaging, therefore, is not primarily to diagnose disease, but to aid in both surgical staging and in the evaluation of potential clinical "blind spots." In this article, the normal anatomy of the larynx is reviewed, with special attention to important surgical and functional structures.

Functional and clinical anatomy of the posterior insertion of the human vocal ligament

The suggested methods of the formation of intubation granuloma as well as carcinoma invasion in the area of posterior vocal ligament insertion have been controversial. One reason for divergent opinions is possibly based on different judgements of morphology in this region. The present study analyzed structures of the vocal ligament and vocalis muscle insertion at the vocal process by means of histological, immunohistochemical and electron microscopic methods. Investigations were performed in three planes on the vocal cords of 22 men and 19 women (aged 21-97 years). Inside the insertion zone of the vocal ligament at the vocal process three structures could be distinguished: hyaline cartilage at the base of arytenoid cartilage, elastic cartilage at its apex and the posterior elastic nodule in front of them. No perichondrium could be seen around the elastic nodule. In elastic nodules type I and type III collagen fibrils as well as elastic fibers formed a scissor-like meshwork around large fibroblasts. The vocalis muscle inserted at the perichondrium in the lateral part of the arytenoid skeleton by short tendons. At the insertion zone blood vessels of the vocalis muscle penetrated the perichondrium and reached the cartilaginous matrix. At the beginning of osteogenesis, the blood vessels connected with intraosseous blood vessels of the arytenoid. Connective tissue cells of the insertion zone and extracellular matrix components formed by these cells fulfilled a biomechanical function by equalizing the different elastic moduli of tendon, cartilage or bone. The lack of perichondrium around the lengthened posterior elastic nodule made formation of intubation granulomas caused by perichondritis in this area impossible. Loosened perichondrium or periosteum in the area of the insertion of the vocalis muscle at the vocal process, ossification and associated vascularization of the arytenoid skeleton permitted invasion of carcinomas into the arytenoid.

Anatomical considerations of closure of the laryngeal vestibule during swallowing

Morphologic correlates of physiologic closure mechanisms of the laryngeal vestibule were investigated in plastinated serial sections of 25 normal adult larynges. The anterior part of the laryngeal vestibule was seen to be bounded by the epiglottis and the thyroepiglottic ligament medially, and by lateral extensions of the periepiglottic adipose tissue laterally. The posterior part of the laryngeal vestibule was bordered by the aryepiglottic folds. Morphologically, the periepiglottic space and the aryepiglottic folds were completely separated by several transversely oriented collagenous fiber layers attached to the thyroid perichondrium laterally. This may suggest a corresponding functional separation, as described previously in the literature. Closure of the anterior part of the laryngeal vestibule during swallowing is probably related to the lowering of the epiglottis, with both depending on pressure exerted onto the periepiglottic adipose tissue. Closure of the posterior part of the laryngeal vestibule is most likely related to closure of the rima glottidis, with both depending on adduction of the arytenoid cartilage.

An anatomic study of the rat larynx: establishing the rat model for neuromuscular function

The gross and microscopic anatomy of the rat larynx was studied with particular attention to myology and neuromuscular structures to further validate it as a model to evaluate morphologic and functional changes induced by botulinum injection. A laryngeal alar cartilage (LAIC), alar cricoarytenoid (ACA) muscle, and a superior cricoarytenoid muscle (SCA) were identified as anatomic structures not previously described. Two portions (medial and lateral) of the thyroarytenoid muscle (TA) were distinguished. The function of the ACA was suggested to be similar to the aryepiglottis muscle in humans and the function of the SCA was suggested to be similar to the human interarytenoid muscle. The predominant pattern of motor endplate (MEP) distribution in rat laryngeal muscles (posterior cricoarytenoid, lateral cricoarytenoid, cricothyroid, and SCA) was to have MEPs concentrated mostly at the midbelly of muscle where they were distributed throughout the cross-sectional area of the midbelly. The TA and ACA differed from this pattern. The lateral TA had MEPs concentrated at the anterior third of its belly and those of the medial TA were located at the midbelly. Motor endplates in the ACA were located mostly at the posterior portion of muscle. Muscle fiber-typing showed subtle differences between the intrinsic laryngeal muscles. Fast fibers were predominant in the rat laryngeal muscles. This study supports the expanded use of rats in studies of laryngeal neuromuscular function and disease in humans.

The lateral thyroid ligament of Berry

Division of the lateral thyroid ligament is essential for total thyroid lobectomy. The exact extent of this ligament, first described by Berry in 1888, was studied in a series of 25 cadaveric and post-mortem subjects. The ligament was attached to the inferior margin of the cornu of the cricoid cartilage, near its pole, and extended infero-medially onto the tracheal wall, reaching the midline in 4 of the 50 lobes examined. At the level of the cricoid cartilage, the mean distance between the attachment of the ligament to the cricoid cartilage and the recurrent laryngeal nerve (RLN) entry point into the larynx was 1.9 mm. This region corresponds to the area where RLNs are mostly injured during thyroid surgery. Awareness of the extent of this ligament and the proximity of the RLN to it should lessen the risk of injury to the RLN during thyroid lobectomy and total thyroidectomy.

[The difficult intubation. The value of BURP and 3 predictive tests of difficult intubation]

The value of BURP (= backwards-upwards-rightwards-pressure of the larynx) was tested as a improvement of the visualisation of the larynx. Simultaneously we wanted to assess the value of different predictive tests of a difficult intubation, which are easy to perform as bedside tests.

PATIENTS AND MATERIAL

1993 patients of all different surgical clinics in a tertiary care hospital in Switzerland were tested, the complete anaesthesiological staff was involved. We registered the original Mallampati classes, the thyromental distances of Patil and Frerk and the difference of the jugulomental distances in maximally reclined and neutral head position according to Chow. Every anaesthetist also noted his personal, subjective opinion of a possible difficult intubation. Under optimal conditions for intubation we assessed the grade of laryngoscopy according to Wilson and applied BURP if the grade was 3 or higher. Both laryngoscopic grades and the difficulty of intubation were noted.

RESULTS

In our study we found 12.5% awkward (Wilson G3-G5) and 4.7% difficult (Wilson G4-G5) laryngoscopies. These could be changed with BURP into 5.0% and 1.9% respectively. With BURP we found 1.8% of difficult intubations. During our study we did not find any patients, whom we could not intubate either with a mandrin inside the tube or with help of the fiberoptic. The relation between sensitivity and specificity was in all single predictors and in two combinations very low. Our personal subjective predictions proofed to be better, but the rate of false negatives was too high for clinical use.

CONCLUSION

BURP is a valuable method for rendering the majority of difficult laryngoscopies into easy ones. It is very easy to learn and does not need any additional equipment. Three commonly used and recommended predictive tests of the difficult intubation proofed to be of little use in clinical practice.

The human aerodigestive tract and gastroesophageal reflux: an evolutionary perspective

In order to appreciate fully the nature of supraesophageal complications of gastroesophageal reflux in humans, it is essential to view the problem within an evolutionary framework. Examination of the aerodigestive tract anatomy of our mammalian relatives shows that this region in humans is highly derived as compared to other mammals. Among the specializations that adult humans exhibit is a caudal position of the larynx, which results in a permanently expanded oropharynx. These anatomical features underlie our distinctive breathing and swallowing patterns and provide the substrate that allows for the production of articulate speech. While the selection factors that have shaped human evolution obviously favored our derived aerodigestive tract, aspects of this anatomy appear particularly unsuited to accommodate gastroesophageal reflux. Indeed, our unique aerodigestive tract morphology may predispose us to an array of supraesophageal complications of gastroesophageal reflux.

Three-dimensional endoscopic mode for observation of laryngeal structures by helical computed tomography

We produced high-quality three-dimensional (3D) endoscopic images of the larynx using helical scanning computed tomography. Subjects included two normal volunteers and 10 patients: five with laryngeal cancer, four with unilateral recurrent laryngeal nerve (RLN) palsy, and one with atrophied vocal folds. Two vertically split hemilaryngeal images were displayed together with the oral and tracheal views. Although motion artifacts were seen in four patients, laryngeal structures including the vocal fold, ventricular fold, and ventricle were clearly identified in all subjects. In the patients with cancer, axial images showing the extent of the tumor in each patient provided more information than 3D endoscopic images. In the patients with RLN palsy and atrophied vocal fold, combination of 3D endoscopic and cross-sectional images offered more diagnostic information than axial images alone.

Measurements of airway dimensions and calculation of mass transfer characteristics of the human oral passage

This paper presents measurements of the geometric shape, perimeter, and cross-sectional area of the human oral passage (from oral entrance to midtrachea) and relates them through dimensionless parameters to the depositional mass transfer of ultrafine particles. Studies were performed in two identical replicate oral passage models, one of which was cut orthogonal to the airflow direction into 3 mm elements for measurement, the other used intact for experimental measurements of ultrafine aerosol deposition. Dimensional data were combined with deposition measurements in two sections of the oral passage (the horizontal oral cavity and the vertical laryngeal-tracheal airway) to calculate the dimensionless mass transfer Sherwood number (Sh). Mass transfer theory suggests that Sh should be expressible as a function of the Reynolds number (Re) and the Schmidt number (Sc). For inhalation and exhalation through the oral cavity (O-C), an empirical relationship was obtained for flow rates from 7.5-30.0 1 min-1: Sh = 15.3 Re0.812 Sc-0.986 An empirical relationship was likewise obtained for the laryngeal-tracheal (L-T) region over the same range of flow rates: Sh = 25.9 Re0.861 Sc-1.37 These relationships were compared to heat transfer in the human upper airways through the well-known analogy between heat and mass transfer. The Reynolds number dependence for both the O-C and L-T relationships was in good agreement with that for heat transfer. The mass transfer coefficients were compared to extrathoracic uptake of gases and vapors and showed similar flow rate dependence. For gases and vapors that conform to the zero concentration boundary condition, the empirical relationships are applicable when diffusion coefficients are taken into consideration.

Volume estimation of the preepiglottic and paraglottic space using spiral computed tomography

The purpose of this study was to estimate the volume variability of the preepiglottic and paraglottic space in the normal larynx. In 23 adult patients (12 women, 11 men), a spiral CT acquisition through the larynx was obtained. No laryngeal pathology was observed. The area of the this submucosal fat space was estimated on each slice by semi-automatic segmentation; the volume was calculated by the summation-of-areas technique. The obtained volumes were correlated with body area, body mass index and gender. The mean estimated volume of the preepiglottic and paraglottic space was 2.8 ml (SD 1.7 ml, range 0.7-5.9). No correlation with body mass index (p = 0.6), but a significant correlation with body area (p < 0.001) was found. A significant volume difference was present between men (mean 4.5 ml, SD 1.0 ml, range 2.8-5.9) and women (mean 1.4 ml, SD 0.5 ml, range 0.7-2.4)(p < 0.0001). Multiple regression analysis showed gender (p < 0.0001) to be a more important variable than body area (p = 0.17) in predicting the volume of the preepiglottic and paraglottic space. In conclusion, the volume of the preepiglottic and paraglottic space appears to be very variable, and should only be analysed with consideration of the gender of the examined subjects.

Ultrasonographic imaging of the tongue and larynx in normal dogs

Ultrasonographic imaging of the tongue and larynx was performed in 10 dogs with no previous history of upper airway disease. The ultrasonographic findings were compared with the normal canine anatomy of this area and with the results described in the human literature. This study shows that the anatomical features of the canine larynx are adequately detectable using ultrasonography. This finding is in accordance with the findings described in the human literature. It is concluded that ultrasonography may offer a means of investigating canine laryngeal abnormalities.

Phonatory characteristics of patients undergoing thyroidectomy without laryngeal nerve injury

Complications that arise after thyroid surgery may be associated with infection, hemorrhage, hormonal problems, and laryngeal nerve injury. Voice alteration after thyroidectomy is usually caused by recurrent or superior laryngeal nerve injury. This voice dysfunction may also be associated with laryngotracheal fixation with impairment of vertical movement or by temporary malfunction of the strap muscles after surgery. In this study, we evaluated the voice function phonetically before and after thyroidectomy in 54 patients, although function of the recurrent and superior laryngeal nerves was normal. During surgery, the superior and recurrent laryngeal nerves were identified and protected, and after surgery electromyographic testing of the cricothyroid muscle was performed. Typical voice symptoms after surgery were easy fatigue during phonation and difficulty with high pitch and singing voice. Acoustic analysis revealed that the phonation time and fundamental frequency were not changed after surgery, but the speaking fundamental frequency, range of speaking fundamental frequency, and vocal range were significantly diminished after surgery. These data allowed us to suggest that the cause of voice dysfunction is not seen in neural lesions, but in a disturbance of the extralaryngeal skeleton. These voice changes emphasize the importance of the extralaryngeal mechanism for pitch control.

The effect of age, sex, obesity and posture on upper airway size

Most patients with sleep apnoea/hypopnoea syndrome (SAHS) are middle-aged men. As there are conflicting data on the effects of age and gender on upper airway calibre, we tested the hypothesis that increasing age and the male sex predispose to upper airway narrowing in normal subjects. We measured upper airway calibre using acoustic reflection in 60 men and 54 women (median 35, range 16-74 yrs) both seated and supine. All upper airway dimensions, except oropharyngeal junction (OPJ), decreased with increasing age in both men and women (r > -0.24, p < or = 0.05) while supine (r2 > 0.06). Men had greater changes in airway area at OPJ on lying down (mean (SEM) 0.5 (0.1), 0.2 (0.1) cm2; p < 0.02). Men had greater body mass indices (mean (SD) 26 (4), 24 (4) kg.m-2; p = 0.04), and larger neck circumferences (mean (SD) 38 (3), 33 (2) cm; p < 0.0001) than women. For any body mass index, neck circumference was larger in men than women (p < 0.001). This study shows that upper airway size decreases with increasing age in both men and women, and that men have greater upper airway collapsibility on lying down at oropharyngeal junction than women.

Elastic structures in the vocalization apparatus of the Túngara frog Physalaemus pustulosus (Leptodactylidae)

Histological analysis of the vocal sac and body wall in the leptodactylid frog Physalaemus pustulosus suggests that both muscle and elastic fibers are important in call production. Abdominal musculature as well as abdominal bands of elastin (the lineae masculinae) provide the energy required for exhalation and sound production. Air flowing through the larynx inflates a highly extensible vocal sac lined with muscle and a network of elastic fibers. Inherent elasticity together with muscular activity of the vocal sac likely increase the speed and possibly decrease the energetic costs of lung reinflation following vocalization. The mechanics of call production in P. pustulosus thus involve not only laryngeal activation but also elastic transfer of air between the supralaryngeal vocal sac and abdominal respiratory structures.

Surgical anatomy of the larynx

Modern functionally oriented surgery of the larynx increasingly requires exact knowledge of the anatomy and landmarks of the endolaryngeal structures in relation to the laryngeal skeleton. Review of the literature reveals several opposing statements and controversial anatomical definitions regarding several clinically critical points. In order to obtain basic anatomical data morphological measurements were performed on a total of 50 laryngeal specimens. Measurements were taken on whole organs and on cuts in the horizontal and in the frontal plane, as well. The data were evaluated statistically, which resulted in the determination of average configurations and dimensions of cartilages and soft tissues of the larynx. In particular, the projection of the deeper structures on the surface and the distances and angles between the different structures were taken into consideration. In order to make these data clinically applicable a scale model has been developed that will allow a direct correlation and application for individual surgery.

Barrier between the supraglottis and the glottis: myth or reality?

Controversial opinions on the existence of a "barrier" between the supraglottic and glottic regions of the larynx are reported. Even if the two areas have different embryological derivations, there is no anatomic evidence of a "barrier" that could prevent supraglottic cancer from extending downward to the glottis. Numerous adequate pathologic studies, including whole organ sections, confirm that for advanced cancers, anatomic compartments delimiting the spread of the neoplastic process from the supraglottis to the glottis do not exist. Therefore, supraglottic laryngectomy should be performed not on the basis of embryological considerations, but on the basis of the actual extension of the neoplastic lesion.

Foramen thyroideum: a comparative study in embryos, fetuses, and adults

The incidence and characteristics of foramen thyroideum (FT) in embryonic and/or fetal larynges have not been established. In the present study, 90 adult larynges and 53 embryonic-fetal larynges were studied. The incidence of FT during the embryonic-fetal period (57%) was statistically different from the adult period (31%) (P = 0.005). All the FT found in the adult period contained vessels and/or nerves, while in the embryonic and fetal period only 63% presented neurovascular elements (P < 0.001). The origin of FT in the embryonic period and its persistence during adult life is discussed.