The shear modulus of the human vocal fold, preliminary results from 20 larynxes

Quantification of the elastic properties of the human vocal fold provides invaluable data for researchers deriving mathematical models of phonation, developing tissue engineering therapies, and as normative data for comparison between healthy and scarred tissue. This study measured the shear modulus of excised cadaver vocal folds from 20 subjects. Twenty freshly excised human larynxes were evaluated less than four days post-mortem. They were split along the saggital plane and mounted without tension. Shear modulus was obtained by two different methods. For method 1 cyclical shear stress was applied transversely to the mid-membranous portion of the vocal fold, and shear modulus derived by applying a simple shear model. For method 2 the apparatus was configured as an indentometer, and shear modulus obtained from the stress/strain data by applying an established analytical technique. Method 1 shear model for male larynxes yielded a range from 246 to 3,356 Pa, with a mean value of 1,008 and SD of 380. The range for female larynxes was 286–3,332 Pa, with a mean value of 1,237 and SD of 768. Method 2 indentometer model for male larynxes yielded a range from 552 to 2,741 Pa, with a mean value of 1,000 and SD of 460. The range for female larynxes was 509–1,989 Pa, with a mean value of 1,332 and SD of 428. We have successfully demonstrated two methodologies that are capable of directly measuring the shear modulus of the human vocal fold, without dissecting out the vocal fold cover tissue. The sample size of nine female and 11 male larynxes is too small to validate a general conclusion. The high degree of variability in this small cohort of subjects indicates that factors such as age, health status, and post-mortem delay may be significant; and that there is range of ‘normality’ for vocal fold tissue. This project received financial support from the Engineering Physics and Science Research Council of Great Britain (EPSRC) and the Eugene B Casey Foundation (JBK).     

Paradoxical vocal fold motion: a sensory-motor laryngeal disorder

OBJECTIVES: The purpose of this study is to determine the laryngeal sensitivity (LS) thresholds and the ratings of laryngopharyngeal reflux symptoms in patients with paradoxical vocal fold motion (PVFM). METHODS: This is a chart review following Institutional Review Board approval of 75 patients from January 2006 to June 2007. The patients were diagnosed with PVFM following case history, transnasal flexible laryngoscopy and spirometric testing. The data analyzed consisted of the reflux symptom index (RSI) and laryngopharyngeal sensitivity (LS). Laryngeal sensitivity and RSI were graded according to mild, moderate, or severe. RESULTS: There were 12 (16%) patients with normal RSI scores, 37 patients (49.3%) with moderate RSI (RSI 11-22), and 26 patients (34.7%) with severe RSI (RSI >22). The right LS was normal in 11 patients (14.7%), moderately impaired in 16 patients (21.3%), and severely impaired in 48 (64%) patients. The left LS showed normal sensation in 11 patients (14.7%), moderately impaired LS in 13 patients (17.3%), and severe impairment in 51 patients (68%). Only one patient had both normal sensation and normal RSI, and 70.4% of patients had abnormal RSI and sensation thresholds. CONCLUSIONS: Patients diagnosed with PVFM had a high prevalence of symptoms related to LPR and markedly reduced LS. These findings suggest that PVFM may be triggered by reduced peripheral sensation or laryngeal inflammation.     

Imaging of the calf vocal fold with high-frequency ultrasound

Objectives/Hypothesis: High‐frequency ultrasound imaging offers the potential for assisting in the diagnosis and treatment of vocal fold pathology if it allows aspects of vocal fold microstructure to be visualized noninvasively. The objective of this study was to assess the ability of high‐frequency ultrasound to image vocal fold anatomy and injected biomaterials. Study Design: The vocal folds of two excised calf larynges were imaged ex vivo and compared with corresponding histological sections. Methods: High‐frequency ultrasound imaging was performed under saline submersion using 40 and 50 MHz transducers, and corresponding cryostat cross‐sections were stained with H&E, Trichome, and Verhoeff's Van Gieson stains. Results: The epithelial surface, lamina propria, and underlying muscle were easily identified with the high‐frequency ultrasound as verified with histological sections representing each imaged region. The arytenoid cartilage vocal process can also be clearly distinguished from the surrounding tissue, as can the full extent of injected biomaterials within the superficial lamina propria. Useful ultrasound resolution was obtained to depths of at least 10 mm within the tissue with the 40 MHz transducer. Conclusions: This preliminary study demonstrates the capability of high‐frequency ultrasound to image the layered anatomy of the calf vocal fold and to discern materials injected into the superficial lamina propria, indicating that this technology holds a strong potential for use in phonosurgery.     

Laryngeal adductor reflex hyperexcitability may predict permanent vocal fold paralysis

Laryngeal adductor reflex–continuous intraoperative neuromonitoring (LAR-CIONM) is a novel method of continuous intraoperative neuromonitoring. In contrast to other vagal nerve monitoring techniques, which elicit a laryngeal compound muscle action potential, LAR-CIONM elicits a laryngeal reflex response (LAR). In 300 nerves at risk monitored with LAR-CIONM, two patients have had postoperative permanent vocal fold immobility (VFI). Both patients exhibited a significant LAR amplitude increase prior to complete loss of signal. No other patients have exhibited LAR hyperexcitability. If confirmed in a larger sample, this represents the first time that a vagal intraoperative neuromonitoring technique can distinguish transient from permanent VFI, which could improve patient outcomes. Laryngoscope, 2019 Laryngoscope, 130:E625–E627, 2020     

Histopathologic investigations of the unphonated human vocal fold mucosa

Conclusion. Vocal fold vibration (phonation) after birth is one of the important factors in the growth and development of the human vocal fold mucosa. Objectives. Stellate cells in the maculae flavae located at both ends of the vocal fold mucosa are inferred to be involved in the metabolism of extracellular matrices. Maculae flavae are also considered to be an important structure in the growth and development of the human vocal fold mucosa. Tension caused by phonation (vocal fold vibration) is hypothesized to stimulate stellate cells to accelerate production of extracellular matrices. Vocal fold mucosae unphonated since birth were investigated histologically. Subjects and methods. Vocal fold mucosae, which were unphonated since birth, of three younger adults (17, 24, 28 years old) were investigated by light and electron microscopy. Results. Vocal fold mucosae were hypoplastic and rudimentary and did not have a vocal ligament, Reinke's space or a layered structure. The lamina propria appeared as a uniform structure. Some stellate cells in the maculae flavae showed degeneration. Not many vesicles were present at the periphery of the cytoplasm. The stellate cells synthesized fewer extracellular matrices, such as fibrous protein and glycosaminoglycan. Cytoplasmic processes of the stellate cells were short and shrinking. The stellate cells appeared to have decreased activity.     

Laterofixation of the vocal fold using an endo-extralaryngeal needle carrier for bilateral vocal fold paralysis

Objectives

Laterofixation of the vocal fold is a simple and reliable surgical intervention for laryngeal obstruction due to bilateral vocal fold fixation to obtain sufficient glottal space. Nevertheless, it has some technical disadvantages. This report summarizes the surgical outcomes in patients who underwent laterofixation of the vocal fold with or without the use of an endo-extralaryngeal needle carrier (EENC).

Methods

A prospective study of 11 consecutive patients with bilateral vocal fold paralysis. All of the patients underwent unilateral vocal fold laterofixation. Six patients were assigned to the non-EENC group and five to the EENC group. The surgical outcomes were evaluated, including the operating time and respiratory and phonatory functions.

Results

The operating time was 44% shorter in the EENC group and less skin incisions were required. Postoperatively, the dyspnea was eliminated in all of the patients in both groups, and the six patients who required a tracheotomy were successfully decannulated. Spirometry confirmed the improvements in %FEV₁ and %PEF in the two groups. Postoperative voice function was socially acceptable in all patients, and it tended to be better in the non-EENC group. In the EENC group, one patient developed a minor submucosal hematoma and another patient had a recurrence of dyspnea 2 months postoperatively, probably due to thread disruption.

Conclusion

The present study confirms that laterofixation of the vocal fold with or without EENC relieves laryngeal obstruction. Surgery with the EENC is simpler and quicker than the conventional procedure. However, the surgery with the EENC has some disadvantages, including likely problems with the thread and downward traction on the vocal fold. Surgeons should be aware of these possible shortcomings.     

In vivo measurement of the shear modulus of the human vocal fold: interim results from eight patients

The shear modulus of the vocal fold is an essential parameter required to enhance our understanding of how the vocal fold operates, to develop mathematical models of phonatation, and to provide benchmarks to quantify the effectiveness of surgical procedures. The authors announced the successful deployment of an instrument to measure vocal fold elasticity in vivo last year, and now present the data taken from eight patients in vivo. The shear modulus was measured at the mid-membranous point, in a transverse direction with respect to the axis drawn between the anterior commissure and vocal process. The range of mean shear modulus results is 701–2,225 Pa, with a mean value of 1,371 Pa.     

喉外伤后声门旁注射肝细胞生长因子预防声带瘢痕形成的实验研究*

目的观察兔声带外伤局部注射肝细胞生长因子(hepatocyte growth factor,HGF)后组织病理学、增殖细胞抗原(proliferating cell nuclear antigen, PCNA)及主要细胞外基质（extracellular matrix,ECM）的变化特点。方法对40只实验用兔80侧声带进行锐性损伤,将兔随机分为治疗组和创伤组,另随机选5只试验兔作为对照组。治疗组于损伤后即刻在声门旁注射HGF,创伤组则注射生理盐水。损伤后1周～6个月时采用HE染色、免疫组化染色、ELISA测定及Masson染色法,观察声带组织学结构变化、PCNA及固有层内透明质酸（hyaluronic acid, HA）、胶原纤维等主要ECM的分布及含量变化。结果创伤组声带损伤3个月后局部开始出现瘢痕挛缩,以胶原纤维为主的大量纤维组织增生,6个月时仍紊乱分布于声带固有层各层,损伤后3个月内 PCNA增强(P<0.05),6个月内胶原纤维含量明显高于正常对照组(P<0.05),HA增加不明显。治疗组6个月时形态接近正常,早期的HA、PCNA的表达明显高于创伤组(P<0.05),中、后期差异性消失,胶原纤维含量在3月内有增高趋势,其后稳定,但总体水平均明显低于创伤组(P<0.05)。结论声门旁注射HGF后具有促进声带ECM分泌、合理分布及部分有序化排列的功能,具有促进声带修复再生的作用。