Etiology And Pathophysiology Study On Dysfunctional Vocal Fold Lesions

Voice disorders has a very high prevalence in the crowd. In the American common crowd the rate of having ever got voice disorders in the whole life is 29%. Our country still lacks the accurate prevalence data. However, there are l,300million populations in our country. Estimating at the rate, the population have ever got voice disorder in the whole life in our country will reach hundred million . Dysfunctional vocal fold lesions ( vocal fold nodule, vocal fold polyp, chronic laryngitis , Reinke's edema) are the most common disorders with dysphonia. However, the cause and exact mechanism of these diseases are still unclear. And the current measurements are not effective for all the patients to recover optimal phonation function. Therefore, thorough research is quite necessary . In order to provide basis for prevention and guidance for patients recovering, also providing clues for the mechanism research, this study investigated the risk factors that may relate with these disorders . Another part of the current study is about vocal fold Extracellular Matrix of these two lesions-vocal fold polyp and Reinke's edema. First, histological study was performed to take an insight of morphological alteration of fibroblast, collagen and elastic fibers. Secondary, we undertook study on gene modulation of their mechanism.Part One case-control survey on risk factors of benign vocal fold lesions321 cases who were performed laryngoscope during November, 2004 to May, 2005 in ENT department of the P.L.A. general hospital were invited to participate the survey. Among them 168 cases were diagnosed by laryngoscope as vocal fold nodule, vocal fold polyp, chronic laryngitis , Reinke's edema. They composedthe case group. Another 153 cases were diagnosed by laryngoscope as normal larynx, who composed the control group. Each case were undertook the same questionnaire to investigate the possible risk factors. Logistic regression analysis demonstrated the occurring of benign vocal fold lesions positively correlated to five factors, including occupation, work environment noise, alcohol-consuming, voice-using hours per day and abuse of voice. Occupations which use voice more had higher occurring risk. Vocal fold polyp had positive relationship to the same factors. Excessive voice users had high risk and with increasing of hours using voice per day, the risk increased. The result suggested that in order to decrease the prevalence of these disorders, people should abstain from alcohol, lowering the environment noise, prevent overuse and abuse of voice. It is especially important for the professional voice users, e.g. teachers or managers. The essential therapy for these disorders is to correct bad phonation habits.Part Two Electron Microscopic Observation of fibroblast, Collagen and Elastic Fibers of Extracellular Matrix of vocal fold polyps and Reinke's edemaIn this section, we studied operation-removed simples of 10 vocal fold polyps, 2 vocal cord polyps companied with Reinke's edema , 1 Reinke's edema and 3 normal vocal folds by transmission electron microscopic and scanning electron microscopic. The purpose was to observe histologically the fibroblast, Collagen and elastic fibers in Extracellular Matrix(ECM). The result showed that in the lamina propria of vocal fold polyp and Reinke's edema, the quantity of fibroblast increased and they had abundant organelles, suggesting the fibroblast were in the status of activation. As the main cell to produce lamina propria ECM, the representation hinted the ECM metabolism was active under pathologic circumstance. We also found that in case of lesions, collagen fibers and elastic fibers arrayed irregularly, losing layered distribution in lamina propria. This maychange vibration characteristic of vocal fold, causing turbulence of mucosa wave, thus led to dysphonia.Part Three mRNA Expression of Extracellular Matrix proteins of vocal fold polyps andReinke's edemaIn this section, using a reverse-transcriptase polymerase chain reaction (RT-PCR), mRNA levels of 9 proteins were measured in 12 vocal fold polyps, 2 Reinke's edema and 5 normal vocal folds. The proteins included procollagen I, collagenase, fibromodulin, fibronectin, tropoelastin exon, lysyl oxidase, elastase, hyaluronic acid synathase 2, hyaluronidase. The result showed that in the vocal fold polyps, mRNA levels of collagenase and fibromodulin descended and levels of fibronectin increased. It is consistent to vocal scar in prevenient research . In the first part of our study, we concluded overuse and abuse of voice were closely related to vocal polyps. Therefore, we speculated phonation trauma and vocal fold restoring to trauma played an important role in pathogenic mechanism.According to what mentioned above, we draw the conclusion as following: Vocal folds trauma caused by overuse and abuse of voice were essential pathogenic factor of vocal fold polyps. Repeated trauma and restoring process led to homeostasis of components in lamina propria ECM destroyed. Collagen fibers and elastic fibers arrayed irregularly, losing layered distribution in lamina propria. This kind of variety may change vibration characteristic of vocal fold, causing dysphonia. Some proteins such as fibromodulin, fibronectin played a role in the process.