Mucocele of the eye: causes, symptoms, diagnosis, treatment

A mucocele is not a "tumor," but a benign, yet aggressively expansive, sinus cyst lined with respiratory epithelium and filled with thick mucus. The primary pathogenic factor is ostial obstruction: mucus continues to be produced, pressure increases, the bone thins and shifts, and a "snapcap-like" remodeling process develops. Bacterial superinfection transforms the lesion into a mucopyocele. Orbital symptoms develop when the cyst spreads through the lamina papyracea, the roof of the orbit, which is why patients often consult an ophthalmologist first. [1]

The frontal and ethmoid sinuses are most often involved; the maxillary and sphenoid sinuses are less commonly involved. Sphenoid mucocele is rare, but it is this type that most often causes severe ophthalmoneurological complications—compressive optic neuropathy and orbital apex syndrome. [2]

Classic complaints include progressive exophthalmos, ocular displacement, diplopia, lacrimation, and a feeling of heaviness in the brow; pain and fever are typical of mucopyocele. Computed tomography (CT) reveals a soft tissue mass with sinus dilation and bone thinning; magnetic resonance imaging (MRI) shows a signal dependent on the proteinaceous/drying content. [3]

The gold standard of treatment today is endoscopic endonasal marsupialization with wide and stable drainage (for the frontal sinus, Draf IIb-III, as indicated). Visual complaints and signs of optic nerve compression are a reason for urgent decompression; the shorter the period of compression, the better the visual outcome. [4]

Code according to ICD-10 and ICD-11

In ICD-10, mucocele of the paranasal sinuses is coded as J34.1 "Cyst and mucocele of the nose and paranasal sinuses." This is the basic, billable code for most clinical situations; codes for complications (e.g., orbital) are added as needed. [5]

ICD-11 uses the category CA0C "Cyst or mucocele of the nose/paranasal sinuses" with post-coordination (localization, lateralization). For orbital complications, appropriate dilators/complication diagnoses are added. [6]

Table 1. Codes for mucocele of the paranasal sinuses

System	Code	Explanation
ICD-10	J34.1	Cyst and mucocele of the nose and paranasal sinuses (main diagnosis). [7]
ICD-11	CA0C	Cyst/mucocele of the nose/sinuses with post-coordination (clarification of the sinus, side, complications). [8]

Epidemiology

Mucoceles are rare in adults, but they are a common cause of slowly progressing exophthalmos of sinusogenic origin. The frontal and ethmoid sinuses are most commonly affected; in reviews, the overall proportion of frontal-ethmoidal mucoceles reaches 70-90%, while wedge-shaped mucoceles account for approximately 1-2% of all cases but carry a disproportionately high risk of visual complications. [9]

According to clinical series, a significant proportion of patients have a history of sinus surgery or facial trauma; primary (idiopathic) and secondary mucoceles (post-surgery/trauma/prolonged inflammation) have been described. Large registries record tens to hundreds of cases per center over decades, emphasizing the rarity and need for expert management. [10]

Table 2. Approximate distribution of localizations (summarized by series)

Sinus	Range of shares
Frontal	35-65%
Ethmoidal/frontoethmoidal	20-45%
Maxillary	8-20%
Sphenoid	1-10% (usually severe ophthalmoneurological manifestations)
Sources in summary: systematic reviews and series 2009–2025. [11]

Reasons

The underlying mechanism is chronic obstruction of the natural ostium (post-inflammatory adhesions, polyposis, post-operative changes, trauma). Rarely, a mucocele forms in an isolated pocket of a "blocked" sinus (anatomical variants) without obvious infection. [12]

Secondary mucoceles occur years or even decades after frontal sinus surgery/frontoethmoidectomy or after trauma; cases have been reported after 10-25 years. In pediatrics, there may be an association with cystic fibrosis and allergic fungal syndrome (AFRS).[13]

Risk factors

Risk factors include previous surgeries/endoscopic interventions, chronic rhinosinusitis (including polyposis), allergic fungal rhinosinusitis, midface trauma, and variations in anatomy (narrow frontal recess, Onodi cell, etc.). Recurrences are more common with insufficient diameter of the created anastomosis or fistula scarring. [14]

Table 3. Risk factors and mechanisms

Factor	How does it increase the risk?
Chronic rhinosinusitis/polyposis	Inflammation → swelling/adhesions → blockage of the anastomosis
Previous surgery/trauma	Scarring/deformation of drainage pathways
AFRS, cystic fibrosis	Viscous secretion + chronic inflammation
Anatomy (narrow frontal pocket, Onodi cell)	Mild obstruction and secretion traps

Pathogenesis

With continued secretion, pressure within the sinus increases, the walls remodel, and the bone thins and bulges. The process doesn't destroy the bone "like cancer," but slowly "pushes" it apart (pressure + osteoclastic remodeling); in areas of minimal resistance, a breakthrough into the orbit or intracranial cavity occurs. [15]

Superinfection transforms the lesion into a mucopyocele, dramatically increasing the risk of orbital phlegmon and subperiosteal abscesses; this is an urgent situation. For the wedge-shaped localization, compression of the optic nerve and orbital apex contents is dangerous; the mechanisms of vision loss are direct compression, ischemia/venous congestion, and, less commonly, "inflammatory" involvement of the nerve. [16]

Symptoms

Frontoethmoidal mucoceles present with exophthalmos, hypoglobus, diplopia, and upper eyelid edema; pain is not necessarily present unless infection is present. With wedge-shaped mucoceles, visual and neuro-ophthalmological complaints predominate: decreased visual acuity, field defects, ophthalmoplegia, and orbital apex syndrome. [17]

Red flags: acute visual impairment, pain behind the eye, ophthalmoplegia, fever - these are grounds for urgent imaging and consultation with an ENT + ophthalmologist; delay increases the risk of irreversible neuropathy. [18]

Classification, forms and stages

It is practical to classify by location (frontal, frontoethmoid, ethmoid, maxillary, sphenoid), etiology (primary vs. secondary – postoperative/posttraumatic), the presence of infection (mucocele vs. mucopyocele), and extension (limited, orbital, intracranial). This grid directly determines the approach and extent of intervention. [19]

Table 4. Clinically significant classification axes

Axis	Options	Tactical value
Localization	Frontal-ethmoidal, maxillary, sphenoid	Choice of approach (Draf IIb-III, midimiatal, sphenoidotomy)
Etiology	Primary / Secondary	Risk of recurrence, volume of reconstruction
Infection	Mucocele/mucopiocele	Urgency and antibacterial therapy
Spreading	Without/with orbital/intracranial	Is a combined team needed?

Complications and consequences

Orbital: subperiosteal abscess, orbital phlegmon, optic nerve compression, orbital apex syndrome, persistent diplopia. Intracranial: meningitis, epidural collections, venous sinus thrombosis. Wedge-shaped mucoceles are rare, but the most dangerous for vision. [20]

Even with urgent decompression, visual recovery is variable and depends on the duration of compression; historically, delays of more than 7–10 days have been associated with worse outcomes. Hence, the low threshold for emergency surgery in ophthalmologic symptoms. [21]

Table 5. Red flags and why they are urgent

Sign	Why is it urgent?
Acute visual impairment/field defect	Compression/ischemia of the optic nerve is possible
Ophthalmoplegia/ptosis	Orbital apex syndrome
Fever, severe pain	Mucopyocele, risk of orbital/intracranial complications

When to see a doctor

Any new visual or orbital complaints associated with sinus symptoms warrant an urgent examination by an ophthalmologist and ENT specialist. Exceptions are inappropriate: even "painless" exophthalmos may conceal a large mucocele. [22]

Patients with previous frontal/ethmoid sinus surgery should be aware of the risk of late secondary mucoceles and seek medical attention if they experience forehead asymmetry, eyelid swelling, or diplopia. Children with AFRS/cystic fibrosis require specialist care. [23]

Diagnostics

Step 1. Clinical Examination and Endoscopy. Anamnesis (surgeries, injuries, polyps), orbital examination, and oculomotor nerve testing are performed. An ENT specialist will perform a nasal endoscopy to assess drainage pathways and signs of infection.

• Step 2. VISUALIZATION.
• CT scan of the sinuses (thin sections, bone window) - a basic method: total "soft tissue" shadow of the sinus with expansion and thinning/erosion of the walls; the direction of expansion (into the orbit/intracranial) is visible.
• MRI complements CT: the mucocele signal is variable (the thicker the protein, the higher the T1 and the lower the T2), thin-walled peripheral enhancement, assessment of the orbital apex and optic nerve. [24]

Step 3. Laboratory. For mucopyocele, infection markers and drainage cultures are performed. Routine biomarkers for mucocele are not specific.

Step 4. Consultation. Ophthalmologist + ENT (rhinosurgeon) ± neurosurgeon/maxillofacial surgeon for intracranial/bone component, anesthesia and urgency plan.

Table 6. What each method provides

Method	Key Finding	For what
CT (bone window)	Sinus enlargement, wall thinning/defects	Growth Route and Access Plan
MRI	Protein content (T1/T2), contact with optic nerve/apex	Risk of neuropathy, decision on urgency
Endoscopy	True opening/scars, pus in mucopyocele	Marsupialization/frontal pocket revision plan

Differential diagnosis

Mucocele vs. mucoretention cyst: the latter does not dilate the sinus or remodel bone. Invasive/noninvasive mycoses, inverted papilloma, sinus cancer, dermoid/epidermoid, frontal encephalocele, dacryocystocele (mucocele of the lacrimal sac) - all these "mimicking" mucocele with orbital symptoms. A combination of CT/MRI and endoscopy is decisive. [25]

Treatment

The basic principle of endoscopic endonasal marsupialization is to create a wide and stable opening, evacuate the contents, and preserve the membrane so that it can epithelialize and become part of the normal drainage system. It is minimally invasive, effective, and has a low risk of recurrence given an adequate window size. [26]

For frontal mucoceles, the choice of technique depends on the anatomy. For medial/central lesions, Draf IIb is sufficient; for extended, recurrent, or "lateral" frontal lesions, Draf III (modified Lothrop procedure) is sufficient. The goal is a single, common opening of the frontal sinuses with good visibility and subsequent care (irrigation, epithelialization monitoring). [27]

Endoscopic sphenoidotomy is the treatment of choice for wedge-shaped mucoceles with optic nerve compression: decompression is performed urgently, sometimes within the first few hours, especially in the setting of acute vision loss/ophthalmoplegia. Even with prompt treatment, the visual outcome is variable, but delays worsen the chances. [28]

In the case of a mucopyocele, antibacterial therapy is added (empirically, taking into account the local flora → based on culture results), but the key is still early surgical debridement. Antibiotics alone are insufficient: without drainage, the lesion recurrs and causes orbital/intracranial complications. [29]

Recurrences are less common with modern endoscopic approaches: retrospective studies indicate a rate of <10% on average, while in centers with navigation and sophisticated technique, the rate is ~0.9-2.2%. The main causes are an inadequately small window, scarring of the frontal pocket, and persistent polyposis/AFRS. Endoscopic examinations and irrigations are necessary in the early postoperative period. [30]

Open/combined approaches (bicoronial, forehead osteoplasty) are useful for extremely lateral frontal lesions, thick osteomal septa, or combined neurosurgical tasks; however, here too the trend is shifting toward advanced endoscopic techniques, including navigation and working flaps (Hadad et al.). [31]

In cases of complex frontal pathology, transorbital endoscopic approaches are considered in collaboration with an ophthalmologist/craniofacial surgeon—a niche solution for lateral views and less-than-perfect anatomy. There are fewer data than for transnasal approaches, but in selected cases, this is an acceptable alternative. [32]

Postoperative care includes regular endoscopic toilets, saline irrigations, monitoring of epithelialization, and treatment of concomitant polyposis/allergies (intravenous steroids, and, if indicated, biologic agents for severe polyposis)—all of which reduce the risk of restenosis. For Draf IIb-III, the use of mucosal flaps/perforated stents to maintain the lumen is discussed. [33]

Optics and vision. In compressive neuropathy, the key is the time to decompression. There are reports of full recovery even with a delay of weeks, but overall, the chances drop after 7-10 days of persistent vision loss. Therefore, the algorithm is: emergency CT/MRI → urgent endoscopic decompression. [34]

What not to do. Treating a mucocele for a long time with medication alone; performing a puncture outside the operating room; delaying surgery if vision loss/ophthalmoplegia occurs; ignoring associated polyposis and care of the frontal recess—this is a direct path to restenosis and recurrence. [35]

Table 7. Local methods and expectations

Method	The essence	When appropriate	Results
Endoscopic marsupialization	Wide window and drainage	The basis for the treatment of most mucoceles	High control, low recurrence [36]
Draf IIb-III	Extended frontal osteotomy	Frontal, lateral, relapses	Patentability with proper care [37]
Open/combined	External approach/craniofacial stages	Very lateral/complex cases	Backup option [38]
Emergency sphenoidotomy	Nerve decompression	Clinical mucocele with vision loss	The chance of recovery is ↑ in early stages [39]

Prevention

Prevention of secondary mucoceles involves high-quality surgery and subsequent care: adequate window width, gentle handling of the mucosa, monitoring for polyps/allergies, and regular examinations. After frontal surgery, explain the "red flags" to the patient and develop a follow-up plan. [40]

Forecast

In terms of orbital symptoms, the prognosis is usually favorable after endoscopic marsupialization: exophthalmos, diplopia, and edema resolve in most patients. The risk of recurrence with modern techniques is low (single percent), but it persists for years, so long-term observation is warranted. The visual outcome of optic nerve compression depends primarily on the duration of compression. [41]

Table 8. Relapse and observation

Indicator	Range/Tip
Recurrence rate	<10% on average; 0.9-2.2% in centers with navigation and wide windows
When it recurs	From months to years (cases have been described after 10-25 years)
Observation	Endoscopic control, irrigation; CT/MRI based on symptoms
Total: retrospectives 2004-2025. [42]

FAQ

Is this an "eye" disease?
The origin is the paranasal sinus, but growth into the orbit causes "eye" symptoms: exophthalmos, double vision, and sometimes decreased vision. ENT surgeons work with ophthalmologists to treat it. [43]

Is it possible to avoid surgery?
No. Medications will improve rhinology, but will not eliminate the anastomosis block. The standard is endoscopic marsupialization/frontal revision. [44]

What should you do if your vision suddenly deteriorates?
Immediately – CT/MRI and urgent decompression (usually endoscopic). Every day of delay worsens the chances of regaining vision. [45]

How often does a mucocele return?
With modern techniques, it's rare; however, late recurrence is possible, so it's important to remain under the care of the surgical team. [46]

How does a mucocele differ from a "cyst" in an image?
A mucoretention cyst does not expand the sinus or "push" the bone, whereas a mucocele does expand and can destroy the septa, extending into the orbit. [47]