Functional endoscopic sinus surgery (FESS) is a procedure that is used to treat sinusitis and other conditions that affect the sinuses. Sinusitis is an inflammation of the sinuses that can cause symptoms such as congestion, headaches, and difficulty breathing through the nose.
FESS is a minimally invasive procedure that is performed using an endoscope, a thin, rigid tube with a camera on the end. The endoscope is inserted through the nostrils, allowing the surgeon to visualize the inside of the nasal passages and sinuses. The surgeon can then remove any tissue or obstruction that is blocking the sinuses, such as swollen or infected tissue.
FESS is generally considered to be a safe and effective treatment for sinusitis and other conditions that affect the sinuses. It can help to alleviate symptoms and improve the overall functioning of the sinuses. However, as with any medical procedure, there are potential risks and complications that should be discussed with a healthcare provider.
History The first recorded instance of endoscopy being used to visualize the nasal passage took place in Berlin in 1901. Alfred Hirschmann, a designer and maker of medical instruments, modified a cystoscope for use in the nasal cavity. In October 1903, Hirschmann published "Endoscopy of the nose and its accessory sinuses." In 1910, M. Reichart performed the first endoscopic sinus surgery using a 7 mm endoscope.
In 1925, Maxwell Maltz created the term "sinuscopy," referring to the endoscopic method of visualizing the sinuses. Maltz also encouraged the use of endoscopes as a diagnostic tool for nasal and sinus abnormalities.
In the 1960s, Harold Hopkins, then a PhD at the University of Reading, used his background in physics to develop an endoscope that provided more light and had drastically better resolution than previous endoscopes. Hopkins' rod optic system is widely credited with being a turning point for nasal endoscopy. Utilizing Hopkins' rod optic system, Walter Messenklinger visualized, recorded, and mapped the anatomy of the paranasal sinuses and the lateral nasal walls - specifically, the mucociliary routes - in cadavers. In 1978, Messerklinger published the book titled "Endoscopy of the Nose" on his findings, and his proposed methods to utilize nasal endoscopy for diagnosis.
Heinz Stammberger, a head and neck surgeon and chair of otolaryngology at the University of Graz where he worked with Messerklinger, was interested by the technique and its implications for pathophysiology and treatment of sinus disease. He adopted the technique, becoming identified with it, and traveled the world to advocate for it. After meeting David Kennedy, a physician at Johns Hopkins University, he worked with him and the surgical instrument maker Karl Storz to develop instruments for use in endoscopic sinus surgery, and coined the term Functional Endoscopic Sinus Surgery. Stammberger and Kennedy published multiple papers on FESS use and technique, and in 1985 the first North American course on FESS was taught at Johns Hopkins Hospital in Baltimore.
There was a rise in the overall number of endoscopic sinus surgery procedures performed between 2010 - 2019 in the UK which coincided with a reduction in the number of open procedures performed over the same period.
The mechanical model and historical context The endoscopic approach to sinus surgery was developed in the 1970s by Heinz Stammberger and Walter Messerklinger in Graz, Austria, and brought to wider international attention largely through the work of David Kennedy at the University of Pennsylvania. Early conceptualization of the procedure was grounded in the physiology of mucociliary clearance: by addressing obstruction at the ostiomeatal complex — the anatomical confluence through which the anterior sinuses drain — normal physiological drainage could, in theory, be restored. The term "functional" was itself a deliberate statement of intent, distinguishing the approach from the more radical ablative operations that had preceded it.
For roughly the first two decades of widespread adoption, the primary outcome measures used to evaluate FESS reflected this mechanical framework. Surgeons assessed patency of the middle meatus, resolution of mucosal edema on CT imaging, and patient-reported symptom scores understood largely in structural terms. The question of what happened after surgery — how the mucosal environment was managed, and whether topical agents could reach operated cavities — received comparatively little systematic attention.
The limitations of the mechanical model Chronic rhinosinusitis is now understood to be a disease driven predominantly by mucosal inflammation rather than by anatomical obstruction alone. Epidemiological and pathophysiological research, accumulated over the past two decades, has made clear that structural abnormalities such as a deviated nasal septum or concha bullosa are neither necessary nor sufficient to produce sinusitis in most patients. The mucosal inflammatory process — involving eosinophilic infiltration, disrupted epithelial barrier function, and in many patients a type 2 immune response — persists after surgery regardless of how completely the anatomy has been addressed.
This has significant implications. If surgery creates open sinus cavities but the underlying inflammatory milieu is unchanged, symptomatic recurrence is predictable. Clinical experience bears this out: long-term outcome data consistently show that the most important predictor of sustained improvement after FESS is not the thoroughness of the dissection but adherence to postoperative medical management, principally with topical intranasal corticosteroids. The surgery, in this reading, does not treat the disease directly. It alters the anatomy in ways that make treatment possible.
FESS as a platform for topical drug delivery
The problem of access The anatomy of the paranasal sinuses makes topical drug delivery inherently difficult in unoperated patients. The natural ostia of the maxillary, frontal, and sphenoid sinuses are small, variably positioned, and functionally oriented to expel rather than admit material from the nasal airway. Scintigraphic and computational fluid dynamics studies have demonstrated that in the intact nose, the vast majority of topically applied solution — whether administered as a spray, drop, or irrigation — is deposited on the nasal floor and anterior nasal passages and does not reach the middle meatus in meaningful quantities, let alone penetrate into the sinus cavities themselves.
This anatomical barrier is not merely a matter of clinical inconvenience. It means that patients with chronic rhinosinusitis (CRS) who use topical corticosteroids as prescribed are largely delivering drug to normal nasal mucosa while the inflamed sinus lining — the actual target tissue — remains untreated. The therapeutic effect of intranasal steroid in unoperated patients with polyp disease likely reflects, at least in part, drug deposition on polypoid tissue that has prolapsed into the nasal cavity rather than penetration of the sinuses proper.
The surgical transformation of delivery Endoscopic sinus surgery materially changes this situation. By removing polyps, opening sinus ostia, and in many cases performing middle meatal antrostomy, uncinectomy, and ethmoidectomy, the surgeon creates a continuous patent channel between the nasal airway and the sinus cavities. The mechanical consequence of this is not only improved mucociliary drainage — it is dramatically enhanced access for topically applied agents.
Deposition studies conducted in the postoperative setting have confirmed this effect experimentally. Using radiolabeled solutions delivered by large-volume saline irrigation, researchers found that penetration into the maxillary and ethmoid sinuses increased substantially following FESS compared with the unoperated state, with some studies reporting increases in intranasal deposition to operated sites exceeding 300 percent relative to the same patient's preoperative baseline. The volume and delivery method of the irrigation matters considerably: large-volume, low-pressure systems (typically 240 mL or more, delivered via squeeze bottle or positive-pressure device) consistently outperform sprays and drops in achieving sinus penetration, and this difference is amplified in operated patients, where the opened anatomy acts as a conduit rather than a barrier.
Work from Harvey and colleagues at the University of New South Wales, published across multiple studies in the 2010s, was particularly influential in systematizing this understanding. Their group demonstrated that posture, irrigation volume, and the degree of surgical opening each independently influenced the proportion of delivered solution reaching target sinonasal sites — a finding that prompted reconceptualization of what the surgery was actually for.
Corticosteroid irrigation post-FESS The practical consequence of improved access is that topical corticosteroids delivered via large-volume irrigation — so-called steroid rinses — become genuinely therapeutic after surgery in a way that spray formulations directed at the intact nose are not. Budesonide respules and mometasone furoate, both off-label for this route of administration in many jurisdictions, are the agents most commonly used; betamethasone and fluticasone preparations have also been studied. Administered via squeeze bottle or NeilMed-style irrigation systems, these solutions can bathe the mucosal surface of operated sinuses directly, suppressing the eosinophilic inflammatory activity that would otherwise drive recurrence.
Clinical trials examining outcomes in patients who performed regular postoperative steroid irrigation versus saline alone have demonstrated benefits in endoscopic appearance, symptom scores, and time to recurrence of polyps. The benefit appears dose-dependent to a degree, and is substantially attenuated in patients with poor operative access — underscoring the dependence of pharmacological efficacy on surgical adequacy.
Systemic absorption of topically administered corticosteroids via this route is low but not negligible, particularly in patients with large residual mucosal surfaces, bilateral polyposis, or compromised mucosal integrity. This consideration does not generally preclude use in adult patients with normal adrenal function, though it warrants attention in children and in those receiving other corticosteroid preparations concurrently.
Long nozzle delivery The use of long-nozzle intranasal delivery systems for corticosteroids and saline irrigation following endoscopic sinus surgery has been proposed as a method to improve topical drug penetration into the paranasal sinuses. Conventional short-nozzle nasal sprays tend to deposit medication predominantly within the nasal vestibule, limiting effective distribution to the surgically opened sinus cavities. In a cadaveric study published in 2019, Muaaz Tarabichi, Mustafa Kapadia, and colleagues compared a conventional short nozzle with a custom-designed long and narrow nozzle using radiolabeled saline and SPECT/CT imaging. The investigators demonstrated that the long nozzle delivered medication beyond the maxillary line and toward the olfactory cleft more consistently than standard devices, while significantly reducing deposition within the nasal vestibule. The study supported the hypothesis that bypassing the nasal valve area through a longer nozzle design could enhance sinonasal drug delivery in post-endoscopic sinus surgery patients, potentially improving the effectiveness of topical corticosteroid therapy in chronic rhinosinusitis management.
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