Normal topography of the conus elasticus. Anatomical bases for the spread of laryngeal cancer

Vocal fold fixation due to proximal stenosis progression complicating idiopathic subglottic stenosis

Purpose

This study examined the incidence and risk factors for vocal fold fixation due to proximal progression of idiopathic subglottic stenosis (ISS) over the course of serial treatments.

Methods

Records of 22 consecutive patients with ISS treated between 2004 and 2016 were retrospectively reviewed. Patient, stenosis, and treatment details were recorded. Cox regression was used to identify independent predictors of vocal fold fixation.

Results

All patients were female and mean age at diagnosis was 46 ± 7 years. In five patients, the stenosis was within 15 mm of the glottis at first treatment. Vocal fold fixation due to proximal stenosis progression occurred in seven (32%) patients. It led to permanent hoarseness due to unilateral vocal fold fixation in two patients and caused airway compromise due to bilateral vocal fixation in two other patients. No airway-related deaths occurred and no patient required a tracheostomy. Stenosis incision using coblation or potassium titanyl phosphate laser, and an initial glottis-to-stenosis (GtS) distance < 15 mm significantly increased the risk of proximal stenosis progression on univariable analysis.

Conclusion

Vocal fold fixation due to proximal stenosis progression is a significant complication of idiopathic subglottic stenosis and causes permanent voice and/or airway sequelae. It should be actively looked for and documented every time a patient is assessed. If a reduction in the GtS distance is observed, definitive surgery should be promptly considered before proximal stenosis progression compromises the efficacy and safety of definitive treatment or, worse, causes vocal fold fixation.

Morphometric Study on the Anatomy of the Fetal Cricoid Cartilage and Comparison between its Inner Diameter and Endotracheal Tube Sizes

Objectives:

The high incidence of respiratory disorders is one of the main problems in perinatal medical care. With the increased use of intubation, the incidence of laryngeal injury causing stenosis has also increased. The principal constriction point in the infant's larynx is the midcricoid area. We sought to provide detailed morphometric data on the anatomy of the cricoid cartilage and its relationship with growth and body characteristics of fetuses at 5 to 9 months of gestational age.

Methods:

Nineteen larynges obtained from 17 stillborn infants and 2 newborn infants ranging in gestational age from 5 to 9 months were studied. Measurements of the cricoid cartilage were made with a millimeter-graded caliper.

Results:

Weight was the variable most correlated with cricoid measurements. The cricoid lumen configuration showed an almost elliptic shape and did not change with gestational age. The mean inner subglottic cricoid area was 19.27 ± 9.62 mm2 and was related to weight and body surface area. Cricoid growth was more pronounced at the outer portion of the cartilage.

Conclusions:

The cricoid lumen configuration was elliptic, and its mean area was smaller than that of available endotracheal tubes. This lumen area was most influenced by weight and height.

Anatomical definition of the subglottic region

BACKGROUND

Due to laryngeal neoplasia, as well as infectious and autoimmune diseases, the subglottic region is of great clinical relevance. However, descriptions of the subglottic structures are inconsistent. The aim of our study was to present a precise analysis of the subglottic region and derive functional and clinical conclusions.

METHODS

Histological, histochemical and immunohistochemical investigations as well as scanning electron microscopy were performed and combined with injection techniques applied to the subglottic region of the larynges of 33 body donors.

RESULTS

The three-dimensional extensions of the subglottic region were newly defined: the inferior arcuate line of the vocal cord was defined as the cranial border. The lower margin of the cricoid is the caudal border. Craniolaterally, the elastic cone and, further caudally, the cricoid form the border. Therefore, the definition presented comprises heretofore unnamed ventral and dorsal parts of the lower larynx. The subglottic region can be described as cylindrical, becoming smaller in the cranial direction, following the elastic cone. The ventral boundary is formed by the median part of the cricothyroid ligament (ligamentum conicum), the dorsal part by the cricoid cartilage. The walls of the subglottis are divided into three or four layers composed of collagenous and elastic fibres in which seromucous glands are embedded. Subglottic blood vessels including a tight subepithelial capillary plexus were delineated.

CONCLUSION

The new definition of the subglottic extensions presented is helpful and essential for precise laryngeal tumour classification. The results indicate that the boundaries are unlikely to counteract tumour progression in the subglottis. Furthermore, the findings suggest that these structures contribute to temperature regulation of breath, protection against inflammation as well as breath frequency and depth-dependent mucus secretion.

Intrinsic and extrinsic forces determine the distortion of the split cricoid ring

OBJECTIVE

An anterior cricoid split (ACS) causes an immediate distortion of the cricoid cartilage resulting in an anterior gap due to retraction of the cut ends. The objective of this animal study is to investigate: (1) to what extent the distortion after ACS is influenced by non-cartilaginous structures like tunica elastica, membranes, ligaments and muscles, which are connected to the cricoid; (2) how distortion is changing with further development; (3) in what way the distortion is affected by scoring of the internal surface of the cricoid; and (4) whether an immediate or late injury-induced distortion is related to age.

METHODS

Surgical interventions were performed in 20 young (8 weeks of age, 1300-1600 g) and 5 adult (28 weeks of age, 3500-4000 g) New Zealand White rabbits. The immediate effects were measured, and then the animals were followed for 20 weeks to study the long-term effects of the various procedures.

RESULTS

(1) The gap, immediately following an ACS, increased after additional transection of the cricothyroid ligament and the cricotracheal membrane, and even more when the cricovocal membrane was elevated from the inner surface of the cricoid arch. (2) The degree of distortion after various interventions in young animals appeared to increase substantially during further growth. (3) When the above-mentioned successive surgical steps were combined with scoring of the internal surface of the cricoid arch, a marked malformation of the split cricoid did develop with warping of the cut ends in lateral direction and a latero-cephalic rotation, the latter due to the action of the cricothyroid muscles. (4) The immediate distortion appeared to be similar in young and adult animals. During a follow-up of 20 weeks, a progressive distortion of the split cricoid ring was observed in the young growing rabbits. In adult animals, no significant progression of the distortion was found.

CONCLUSIONS

The immediate and long-term distortion of the split cricoid is determined by the release of intrinsic forces of the cartilage, and extrinsic forces from non-cartilaginous structures like ligaments, muscles, membranes and tunica elastica.

Morphology of the human larynx during the first five years of life studied on whole organ serial sections

The morphologic development of the human larynx during the first years of life is poorly understood to date. This study used plastinated whole organ serial sections to determine the growth and structure of the infant larynx. The larynges of 43 children 1 to 60 months old were plastinated. Whole organ serial sections were obtained by cutting the resulting specimen with a diamond band saw. The slices were then submitted to computer-assisted morphometric investigation. We found that the subglottic airway rapidly increases in size during the first 2 years of life. Further growth follows a linear mode. The relative proportion of the mucosal lining decreases likewise. In contrast to that in adults, and comparable to that in most mammals, the cartilaginous glottis accounts for 60% to 75% of the vocal folds' length at <2 years. No sexual dimorphism of the larynx exists during childhood. This study supplies detailed morphometric data on the growth and structure of the human larynx during the first years of life. It is the first to use plastinated whole organ serial sections for morphology of the pediatric larynx. Therefore, this study provides quantitative anatomic data of clinical interest that have not been available to date.

The attachments of the conus elasticus to the laryngeal skeleton: physiologic and clinical implications

The attachments of the inferior and dorsal extensions of the lateral parts of the conus elasticus (CE) are not fully understood. A re-investigation was done in plastinated serial sections of 20 adult human larynges. The CE consists of a coherent sheet of connective tissue fibers dividing into two layers toward the inferior anchorage to the cricoid arch, and the posterior anchorage to the cricoid lamina. Caudally, the medial fiber layer is continuous with the submucous fibroelastic membrane of the trachea and is not connected to the cricoid cartilage. The lateral caudal fiber layer is attached to the superior rim of the cricoid arch. Dorsally, both layers of the CE are fixed to the cricoid lamina, the lateral sheet to the lateral edge of the cartilage, the medial sheet to its anterior perichondrium near the midline. Towards the cricoarytenoid joint, the dorsal extension of the CE divides into a caudal and a cranial sheet including a fold of adipose tissue at the base of the arytenoid cartilage. The cranial layer extends towards the vocal process, the caudal layer radiates into the joint capsule and may therefore influence the complicated joint mechanics. The firm attachments of the CE to the cricoid cartilage probably counteract deformations of the CE during phonation. An insufficient fixation of the CE may contribute to an obstruction of the airways causing sleep apnea.