Readers of this blockage will know that I have written often about drug-induced sleep endoscopy (DISE) as an important evaluation for patients with obstructive sleep apnea who cannot tolerate CPAP well. One of the unique benefits of DISE is the assessment of whether the epiglottis might be a cause of obstructive sleep apnea, in that it can fall back or otherwise collapse to block breathing. Those of us who perform DISE are very interested in this because we think it occurs in patients during natural sleep and can even be a reason that patients do not tolerate CPAP (if the CPAP pushes the epiglottis back to block their breathing, the CPAP that is supposed to help improve breathing can actually worsen it).
We have led major, scientifically-rigorous studies including other major sleep surgery centers around the world, examining the association between findings of DISE before surgery and the outcomes of surgery. We are proud of these studies and our colleagues coming together to address this critical question for patient care, in that the main purpose of DISE is to understand how it can help us choose surgeries and/or predict the results. I have written in this blog about the first study that considered most types of throat surgery, and the second study focused on Inspire Upper Airway Stimulation.These studies were the largest studies of their kind, but even they were not able to determine clearly the importance of epiglottis-related obstruction and, more importantly, how to treat it. The reason is that epiglottis-related obstruction occurs in about 5-10% of patients, so these studies did not have enough patients with epiglottis-related obstruction undergoing the various kinds of surgery. I generally think about two procedures to treat epiglottis-related obstruction specifically – hyoid suspension or partial removal of the epiglottis – but we could not determine scientifically whether these were effective treatments in these cases.
Is epiglottis shape a clue to epiglottis-related obstruction?
It would be nice if we had some clues about epiglottis-related obstruction before performing DISE. I do not think DISE is needed before every sleep apnea surgery, but it would be nice to know if there was a reason to expect something less-common like epiglottis-related obstruction. In 2013, I wrote about the role of the epiglottis in obstructive sleep apnea, and in that post I mentioned my observation that in many patients with obstructive sleep apnea who turn out to have epiglottis-related obstruction during DISE, the epiglottis can be positioned further back in the throat and may even have a different shape, even while they are awake.
I want to congratulate Dr. Josie Xu, an outstanding and talented surgeon who completed her fellowship in sleep surgery at our center today. She will be joining the team at North York General Hospital in Toronto, returning to the University of Toronto system where she completed her residency training. She is committed to raising awareness about sleep disorders and sleep surgery, and her skills in graphic design have already led her to make a video posted on YouTube about our field of otolaryngology-head and neck surgery. At North York, she will be one of the few dedicated sleep surgeons in Canada, and I look forward to seeing the incredible things she will accomplish in the years ahead.
One of the wonderful things about having fellows and residents is that they ask thoughtful questions. In this case, Dr. Xu wanted to dive into the literature concerning epiglottis-related obstruction, and she found a study I had not seen before. A Slovenian study from 2019 examined the association between epiglottis shape while awake (seen on awake flexible fiberoptic examination in the office) and the presence of epiglottis-related obstruction during DISE. They found that the typical epiglottis shape, with a gentle curve, had a relatively low likelihood of epiglottis-related obstruction (6%), but a flat epiglottis (common in cases where the epiglottis is positioned more towards the back of the throat) was seen much more commonly (32%). Although these numbers for epiglottis-related obstruction are a little higher than we see, the basic finding of more epiglottis-related obstruction with an atypical epiglottis shape matches exactly what we have seen. I applaud the researchers for their work and systematic evaluation.
The bottom line: epiglottis shape is an important clue but does not replace DISE
This study shows that epiglottis shape may suggest epiglottis-related obstruction but, at the same time, does not indicate that it can replace DISE. Other colleagues have reported on patterns of airflow seen during sleep studies that can be a clue to complete epiglottis-related obstruction, but that also is not usable widely at the present time. The study supports our performing DISE in cases where we are concerned about unexpected findings like epiglottis-related obstruction. For the time being, we will continue our approach and look forward to understanding more about the epiglottis with research from colleagues around the world.