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

Poor 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 the diagnostic utility of 4-mm zero-degree rigid endoscopic laryngeal examination as a tool to predict glottic exposure in microlaryngoscopy (MLS).

Cross-sectional observational study.

This is a cross-sectional study, conducted from March 1, 2022 to November 30, 2023 at the ENT department of a tertiary care hospital in North India. A 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 zero-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 MLS 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 zero-degree laryngoscopy and to compare it with Laryngoscore.

A total of 35 adults participated in the study, of which 28 were men (80%) with a median (range) age of 45 (24-76) years. The area under the curve for zero-degree laryngoscopy and Laryngoscore were 0.97 and 0.83, respectively. The optimal cut-off value (sensitivity, specificity) to identify difficult laryngeal exposure for zero-degree laryngoscopy and Laryngoscore were 1.5 (93.3%, 100%) and 4.5 (80%, 85%), respectively.

Zero-degree laryngoscopy is an excellent predictor of glottic exposure on MLS. Its accuracy surpasses that of the Laryngoscore in identifying an ideal candidate for MLS.