Research News

Cleveland Clinic sinus specialists are zooming in on our nose’s smallest residents to ask one of their biggest questions: why does functional endoscopic sinus surgery (FESS) cure some patients with chronic rhinosinusitis (CRS), but not others? 

 Their answers, published in the Journal of Clinical Medicine, suggest the sinus microbiome may play a role in why some patients can’t find relief from months-long inflammation and infection-like sinus symptoms, even after tissues are removed 

Patients with chronic rhinosinusitis who do not respond to medications or other interventions are candidates for FESS, which is a surgical procedure that physically removes inflamed or obstructing tissues. While it is effective for many, the surgery does not work for everyone. 

Experts, including study lead author Mohamad Chabaan, MD, a head and neck surgeon who specializes in sinus and nose conditions, have looked at several other factors to explain the surgery’s variable outcome. But none of them, including BMI, race, gender, smoking status or medical history, gave a full picture. The research team wondered if the driving force could be more microscopic in nature. The team, which also included (now-graduated) medical student David Hoying, MD, and Naseer Sangwan, PhD, Director of Cleveland Clinic’s Microbial Sequencing & Analytics Core, began investigating the microbes living in our sinus and nose. 

What is the sinus microbiome? 

The sinus microbiome is a community of bacteria, viruses, fungi and other microbes that live in our sinuses and noses. Most of these microbes take up residence during or shortly after birth and can help protect us from harmful germs in the air we breathe. Scientists previously believed the sinuses were sterile because earlier tools weren’t sensitive enough to detect microbes in such small, hard-to-reach spaces. As a result, our understanding of the sinus microbiome is catching up to better-known microbial communities in the gut or on the skin. 

Previous studies have hinted that the sinus microbiome may influence chronic rhinosinusitis, but no single microbe has emerged as a reliable marker of disease or surgical outcome.  

The research team collected nasal swabs from 44 FESS patients between 2021 and 2022 and tracked symptom changes before the procedure and four months postop using surveys. About half the patients reported feeling better after surgery while the other half still had symptoms.  

Dr. Sangwan, an expert in studying trickier microbiomes and their effects on human health, then analyzed the microbes in the swabs to uncover microbial patterns that might help explain this 50/50 split. He found distinct microbial profiles for patients whose symptoms improved compared to those who had not.  

Microbial patterns may influence sinus inflammation 

To begin understanding what, if anything, the bacteria in the sinus microbiome were doing to influence surgery response and persistent inflammation during chronic rhinosinusitis, the team also measured blood levels of inflammatory proteins, called cytokines. 

They found that in addition to their distinct microbial signatures, patients with poorer surgical outcomes also tended to have higher levels of pro-inflammatory cytokines than their peers who benefited from surgery.  

“Looking at both the microbiome and the immune response gives us a more complete picture,” Dr. Sangwan says. “We need to do more targeted studies to confirm cause and effect, but our data suggests that certain microbes may be driving inflammation, potentially interfering with healing even after surgery.” 

The team hopes their work will pave the way for microbiome-informed treatment strategies, like targeted antibiotics or pre-surgical microbiome profiling to predict surgery outcomes and provide more personalized treatments. 

“We’re not just cataloging microbes; we’re trying to connect the dots between what’s living in the sinuses and how patients feel,” Dr. Sangwan says. “If we can understand those relationships, we can start to tailor treatments in ways that really make a difference.”