Using Office-Based Zero-Degree Rigid Laryngoscopy to Predict Glottic Exposure in Microlaryngoscopy

Abstract

OBJECTIVESPoor glottic exposure in microlaryngeal surgery can result in difficult instrumentation or incomplete surgery affecting surgical outcomes. Anticipating poor glottic exposure preoperatively allows surgeons to prepare adequately, ensuring successful surgery. This study aims to determine diagnostic utility of 4mm zero-degree rigid endoscopic laryngeal examination as a tool to predict glottic exposure in microlaryngoscopy. STUDY DESIGNCross-sectional observational study. METHODSThis is a cross-sectional study, conducted from 1st March 2022 to 30th November 2023 at the ENT department of a tertiary care hospital in North India. Total of 35 adult participants who underwent MLS were consecutively enrolled. Participants in whom the lesion was obscuring the anterior commissure and in whom gag reflex prevented complete 0-degree laryngeal examination were excluded from the study. All enrolled participants were evaluated preoperatively with a 4 mm rigid zero-degree laryngoscopic examination and the laryngoscore. The total score on the laryngoscore proforma was calculated and recorded. The visualized glottis on zero-degree laryngoscopy was graded as follows: Grade 1, anterior commissure and the entire glottic plane can be seen; Grade 2, glottis can be seen but not the anterior commissure; Grade 3, only the posterior half of the glottis can be seen; Grade 4, only the arytenoids can be seen. The glottic exposure on microlaryngoscopy was also assessed using the same grading system. Depending on the exposure of the anterior commissure, the cohort was divided into two groups: good laryngeal exposure and difficult laryngeal exposure. Receiver operating characteristic curve analysis was done to evaluate the predictive accuracy of 0-degree laryngoscopy and to compare it with laryngoscore. RESULTSA total of 35 adults participated in the study, of which 28 were men (80%) with median (range) age of 45(24-76) years. The area under the curve for 0-degree laryngoscopy and laryngoscore were 0.97 and 0.83 respectively. Optimal cutoff value (sensitivity, specificity) to identify difficult laryngeal exposure for 0-degree laryngoscopy and laryngoscore were 1.5 (93.3%,100%) and 4.5 (80%,85%) respectively. CONCLUSIONZero-degree laryngoscopy is an excellent predictor of glottic exposure on microlaryngoscopy. Its accuracy surpasses that of the laryngoscore in identifying an ideal candidate for microlaryngoscopy.