Epiglottis shape as a predictor of obstruction level in patients with sleep apnea

Despite a broad range of diagnostic methods, identifying the site of obstruction in the upper respiratory tract in patients with obstructive sleep apnea is not always simple and straightforward. With regard to this problem, we present our observations about the specific shape of the epiglottis in patients with obstruction at the level of the tongue base and/or epiglottis.

One hundred and forty consecutive drug-induced sleep endoscopy (DISE) video recordings of patients with polygraphy-verified obstructive sleep apnea were analyzed by three independent observers. We compared the levels of obstruction using the VOTE classification and the shape of the epiglottis, both as seen during the DISE investigation and in the awake state. We have calculated the interrater reliability for VOTE classification results and epiglottis shape evaluation by three different observers.

Out of 140 patients, there were 52 (37.1%) with a flat epiglottis. Within this group, there were only 3 (6%) cases in which obstructions at the tongue base and/or epiglottis level were not found. In the group with normally convex and omega-shaped epiglottis, obstruction at the tongue base level was observed in 28 patients (31.8%); obstruction at the epiglottis level was observed in 5 patients (5.7%); and obstruction at both the epiglottis and tongue base level was observed in 3 patients (3.4%). Interrater reliability for VOTE classification was poor for V (ICC = 0.414) and good for O (ICC = 0.824), T (ICC = 0.775), and E (ICC = 0.852). Additionally, interrater reliability was excellent for epiglottis shape (ICC = 0.912).

In patients with obstructive sleep apnea, examinations in the awake state and drug-induced sleep endoscopy both showed that in most cases of obstruction at epiglottis and/or tongue base, the epiglottis was flat, i.e., lacking the typical anterior convexity in its upper part. We assume that the change of its shape is a result of degeneration of suspensory apparatus that maintains the shape of the epiglottis and holds it in its position. This could contribute to the better identification of patients with a narrowing at this level, and in turn to better decisions regarding the choice of the most suitable treatment.