Stroboscopic Assessment of Vocal Fold Keratosis and Glottic Cancer

Abstract

Disruption of the normal viscoelastic properties of the superficial lamina propria (SLP) results in aberrant vocal fold vibration and mucosal wave propagation. Therefore, an investigation was performed to determine whether stroboscopy is a reliable method for 1) differentiating invasive glottic carcinoma from intraepithelial atypia or 2) determining the depth of cancer invasion. An analysis was done on the preoperative vocal fold vibration characteristics of 62 keratotic (intraepithelial, 45; cancer, 17) lesions that were subsequently resected by means of microlaryngoscopy. Histopathology and intraoperative mapping were used to specify the depth of invasion. A panel of 4 blinded judges was used to assess the amplitude of vocal fold vibration and the magnitude of mucosal wave activity in the region of the lesion from videostroboscopic recordings. The final comparative data set comprised only those ratings that achieved at least 75% interjudge agreement. Of the 28 intraepithelial lesions that could be reliably evaluated for amplitude of vocal fold vibration, only 2 were normal, with the amplitude reduced in 24 and absent in 2. Of the 30 intraepithelial lesions in which mucosal wave activity could be reliably assessed, only 2 were normal, with the wave reduced in 24 and absent in 4. Furthermore, amplitude of vocal fold vibration and magnitude of mucosal wave propagation were absent in 2 of 4 carcinomas in which the depth of microinvasion did not reach the vocal ligament. According to the findings herein, reduced amplitude of vocal fold vibration and/or mucosal wave propagation associated with keratosis did not reliably predict the presence of cancer or the depth of cancer invasion into the laminae propriae. However, the presence of a flexible mucosal wave probably indicates that there is not extensive vocal ligament invasion. Reductions in the amplitude of vocal fold vibration and in mucosal wave magnitude were usually noted in intraepithelial atypia, despite the fact that there was no invasion into the SLP. The reduced epithelial pliability could be due to bulky keratosis and/or alteration of the SLP occurring as a result of inflammation or fibrovascular scarring.