What are the causes of unilateral infraorbital swelling?

Unilateral Infraorbital Swelling: Causes and Diagnostic Approach

Unilateral infraorbital swelling most commonly results from infectious orbital cellulitis (typically from ethmoid sinusitis), trauma with orbital fracture, or inflammatory orbital disease including idiopathic orbital inflammatory syndrome (IOIS) and IgG4-related disease. 1, 2

Primary Infectious Causes

Orbital cellulitis is the most frequent serious cause, particularly in children, and presents with:

• Eyelid erythema and edema extending to infraorbital region 1, 2
• Proptosis, chemosis, and restricted ocular movements 2
• Fever and pain with eye movement 2
• Ethmoiditis is the causative factor in the vast majority of cases 3
• Can progress to subperiosteal abscess, which requires differentiation by CT imaging 3

Traumatic Causes

Orbital floor fractures are the most common orbital fractures in older children and adults:

• Present with periorbital soft tissue swelling, ecchymosis, and subconjunctival hemorrhage 1
• May cause diplopia from extraocular muscle entrapment in "trap door" fractures 1
• CT orbits is the most accurate method for detecting fractures and associated soft tissue injuries 1
• Hematoma or soft tissue swelling alone can cause infraorbital fullness without fracture 1

Inflammatory and Neoplastic Causes

Idiopathic orbital inflammatory syndrome (IOIS) and IgG4-related orbital disease are critical considerations:

• Can present with unilateral proptosis and infraorbital swelling with subtle or initially normal imaging 4, 5
• May affect lacrimal gland, extraocular muscles, or orbital fat 6, 7
• Requires serum IgG4 levels and inflammatory markers (ESR, CRP) for workup 4

Orbital tumors and lymphoma can manifest as infraorbital masses:

• Lymphoma presents as painless, "salmon patch" conjunctival swelling that can extend to infraorbital region 1
• Sebaceous gland carcinoma may appear as chronic infraorbital inflammation mimicking unresponsive blepharoconjunctivitis 1
• Ocular surface squamous neoplasia can cause chronic conjunctival hyperemia with infraorbital extension 1

Vascular Causes

Carotid-cavernous fistula (CCF) is a critical diagnosis that can present with isolated proptosis and infraorbital swelling:

• May show normal standard MRI initially but requires dedicated vascular imaging 4
• Secondary findings include vascular congestion, extraocular muscle enlargement, and enlarged superior ophthalmic veins 4
• MRA or CTA must be performed urgently when CCF is suspected 4

Diagnostic Algorithm

For acute presentation with fever/systemic symptoms:

• Obtain CT orbits with contrast immediately to differentiate orbital cellulitis from subperiosteal abscess 1, 3
• Look for sinus opacification (especially ethmoid) as the source 3, 2
• Surgical drainage is reserved for deterioration in proptosis, ocular movements, or vision 3

For subacute/chronic presentation without fever:

• MRI orbits with contrast is the initial imaging study to identify masses or inflammatory processes 8
• Add MRA or CTA urgently if proptosis with inferior dystopia is present to rule out CCF 4
• CT orbits with contrast provides complementary osseous detail and may reveal calcifications 4
• Check serum IgG4, ESR, CRP, and consider infectious workup (syphilis, Lyme) based on clinical context 4

For traumatic presentation:

• CT orbits without contrast is the most useful imaging modality for detecting fractures and intraorbital foreign bodies 1
• Add CT head if orbital roof fracture or intracranial injury is suspected 1

Critical Pitfalls to Avoid

• Never dismiss significant unilateral infraorbital swelling as benign—it demands explanation 4
• Standard brain MRI protocols may miss orbital pathology; ensure dedicated orbital imaging with appropriate sequences 4
• Do not delay vascular imaging (MRA/CTA) when proptosis is present, as CCF can have devastating consequences if missed 4
• Do not start corticosteroids without adequate workup, as this masks diagnoses and worsens outcomes in infectious or neoplastic conditions 4, 8
• Subperiosteal abscess cannot be reliably differentiated from inflammatory phlegmon on imaging alone; clinical response to antibiotics guides management 3

Monitoring Requirements

• Serial visual acuity, color vision, pupillary examination, and visual field testing to detect compressive optic neuropathy 4
• Repeat imaging in 2-4 weeks if initial workup is negative and empiric treatment is initiated 4
• Monitor for treatment response with reduction in proptosis, improvement in extraocular movements, and resolution of pain 5