Complications of sinusitis: orbital, intracranial and bony

Topic

Rarely, sinus infection spreads to the eye socket, the brain or the bone of the skull; swelling around the eye or a severe headache needs same-day care.

Updated Nov 12, 2026

See it in 3D: Ethmoid cells · Frontal sinus · Maxillary sinus · Sphenoid sinus · Cavernous sinus

Key points

Orbital complications are the most frequent; the usual source is ethmoid sinusitis spreading through the thin lamina papyracea.
Chandler stages: I preseptal cellulitis, II orbital cellulitis, III subperiosteal abscess, IV orbital abscess, V cavernous sinus thrombosis.
Pain on eye movement, proptosis, limited eye movement, reduced vision or a relative afferent pupillary defect mean the infection is behind the septum: contrast CT of orbits and sinuses.
Intracranial complications come mostly from frontal and sphenoid sinusitis and are commonest in adolescent males.
Pott puffy tumour: doughy swelling of the forehead from a subperiosteal abscess over frontal bone osteomyelitis; image the brain because intracranial pus often coexists.
Cavernous sinus thrombosis: fever, headache, chemosis, proptosis and palsies of nerves III, IV, VI, V1 and V2, often spreading to both eyes.

What it is

The sinuses are separated from the orbit and the brain by thin bone with natural gaps, and their veins have no valves, so infection can pass directly or along veins. Complications are rare but are the reason rhinosinusitis can blind or kill. They are grouped as orbital (the most common, mostly from the ethmoid sinus and mostly in children), intracranial (meningitis, epidural abscess, subdural empyema, brain abscess and cavernous or sagittal sinus thrombosis, mostly from the frontal and sphenoid sinuses and often in adolescent boys), and bony (osteomyelitis of the frontal bone, the Pott puffy tumour). A mucocele is a slow, expanding complication of a blocked sinus. The Chandler stages organise the orbital complications and guide when to image and operate.

Structure

Orbital: preseptal cellulitis, orbital cellulitis, subperiosteal abscess, orbital abscess, cavernous sinus thrombosis (Chandler I to V).
Intracranial: meningitis, epidural abscess, subdural empyema, brain abscess (frontal lobe from frontal sinusitis), cavernous and superior sagittal sinus thrombosis.
Bony: frontal bone osteomyelitis with Pott puffy tumour; maxillary osteomyelitis is rare and seen in infants.
Mucocele: a mucus-filled, expanding sinus with a blocked outflow, most often frontal or frontoethmoid; infected, it becomes a pyocele.
Routes of spread: through thin or dehiscent bone (lamina papyracea, posterior wall of the frontal sinus), along valveless diploic and ophthalmic veins, and through foramina.

Chandler stages of orbital complications of sinusitis

Stage	Where the infection is	Signs	Usual management
I Preseptal cellulitis	Eyelid, in front of the orbital septum	Lid swelling and redness; eye movement and vision normal	Oral or intravenous antibiotics; close review
II Orbital cellulitis	Orbital fat and muscles, behind the septum, no pus collection	Pain on movement, chemosis, proptosis, limited movement	Admission, intravenous antibiotics, CT, ophthalmology and ENT
III Subperiosteal abscess	Pus between the lamina papyracea and the periorbita	Proptosis with the eye pushed down and out	Intravenous antibiotics; drainage if large, vision falls or no improvement
IV Orbital abscess	Pus inside the orbit	Marked proptosis, frozen eye, falling vision	Urgent surgical drainage
V Cavernous sinus thrombosis	Thrombosis spreading to the cavernous sinus	Signs in both eyes, cranial nerve palsies, sepsis	Intensive care, intravenous antibiotics, anticoagulation as decided by specialists

In clinical practice

Child with a recent cold and red swollen eyelids: decide whether the infection is in front of (preseptal) or behind (orbital) the septum; the eye signs make the difference.
Fever with headache, vomiting, drowsiness, neck stiffness, seizures or focal signs in a patient with sinusitis: intracranial complication until imaging says otherwise.
Subdural empyema spreads fast over the brain surface and is a neurosurgical emergency.
Mucocele: slow painless displacement of the eye (down and out from a frontoethmoid mucocele), double vision or a swelling at the inner upper corner of the orbit; CT shows an expanded sinus with thinned walls.
In a diabetic (especially with ketoacidosis) or immunosuppressed patient, facial pain with black or pale nasal crusts and eye signs is invasive fungal sinusitis, not a simple complication.

Next step / Initial management

Any sinusitis with eyelid swelling plus an eye sign (pain on movement, proptosis, chemosis, double vision, reduced vision), or with severe headache, vomiting, drowsiness, neck stiffness or forehead swelling: refer as an emergency, the same day.
Imaging: contrast CT of the orbits, sinuses and brain; MRI when an intracranial collection or venous sinus thrombosis is suspected; lumbar puncture only after imaging rules out a mass effect.
First-line treatment in hospital: intravenous broad-spectrum antibiotics (a third-generation cephalosporin such as ceftriaxone with metronidazole for anaerobes; add vancomycin if MRSA or intracranial spread is a concern), saline irrigation and a short course of topical decongestant.
Ophthalmology checks vision, colour vision and pupils regularly; ENT drains abscesses endoscopically when vision falls, the abscess is large or there is no improvement in 24 to 48 hours; neurosurgery drains intracranial pus.
Diabetic or immunosuppressed patient with nasal necrosis: same-day referral for biopsy and debridement under the suspicion of invasive fungal sinusitis.
Mucocele: routine (or priority, if vision is affected) ENT referral for endoscopic marsupialisation.

Test yourself

Think of the answer, then tap the question to see it.

An 8-year-old with a cold has a swollen right eye, pain on moving it, proptosis and limited abduction. Which Chandler stage is at least present and what is the next test?

At least stage II (orbital cellulitis); a contrast CT of the orbits and sinuses looks for a subperiosteal or orbital abscess. Admit and start intravenous antibiotics.

A 15-year-old boy with frontal sinusitis develops a soft, doughy swelling of the forehead and headache. What is it and why image the brain?

Pott puffy tumour: subperiosteal abscess over frontal bone osteomyelitis; epidural abscess or subdural empyema often coexists, so brain imaging is required.

Which sinus is most often the source of orbital complications and by what route?

The ethmoid sinus, through the thin, sometimes dehiscent lamina papyracea and the valveless ethmoidal and ophthalmic veins.

A patient with sphenoid sinusitis has fever, chemosis and proptosis of both eyes and cannot move either eye laterally. What is the diagnosis?

Cavernous sinus thrombosis (Chandler V); the abducens nerve inside the sinus is often affected first. Intensive care, intravenous antibiotics, specialist decision on anticoagulation.

An adult has slow, painless downward and outward displacement of the left eye and an expanded frontoethmoid sinus with thin walls on CT. What is it?

A frontoethmoid mucocele; it is treated by endoscopic marsupialisation (drainage into the nose).

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Educational content; it does not replace a medical assessment and is not a clinical instruction. For a real case, follow current guidelines and specialist advice.

Sources: Orbital Cellulitis (StatPearls Publishing (NCBI Bookshelf), 2026); Cavernous Sinus Thrombosis (StatPearls Publishing (NCBI Bookshelf), 2025); Pott Puffy Tumor (StatPearls Publishing (NCBI Bookshelf), 2025); Subdural Empyema (StatPearls Publishing (NCBI Bookshelf), 2024); Brain Abscess (StatPearls Publishing (NCBI Bookshelf), 2024); Acute Sinusitis (StatPearls Publishing (NCBI Bookshelf), 2025).

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