What is orbital cellulitis, its typical patient profile, and how is it managed?

Orbital Cellulitis: Comprehensive Overview

Definition and Clinical Distinction

Orbital cellulitis is an infectious inflammatory process involving tissues posterior to the orbital septum within the bony orbit, distinct from preseptal (periorbital) cellulitis, and requires immediate hospitalization with IV antibiotics due to sight- and life-threatening complications. 1, 2

The critical distinguishing features of true orbital cellulitis include:

• Proptosis (forward displacement of the eye) 2
• Impaired or painful extraocular movements 2
• Decreased visual acuity 2
• Ophthalmoplegia 2
• Chemosis (conjunctival swelling) 3
• Diplopia (double vision) 3

In contrast, preseptal cellulitis presents with eyelid erythema and edema but without proptosis, vision changes, or extraocular movement limitation. 2

Epidemiology and Typical Patient Profile

Orbital cellulitis predominantly affects the pediatric population, though it can occur at any age. 3, 4

Common Patient Characteristics:

• Children under 5 years are at highest risk, particularly for ethmoid sinusitis complications 2
• History of upper respiratory tract infection preceding onset is very common 4
• Additional risk factors for postseptal involvement include high neutrophil count, absence of infectious conjunctivitis, gross periorbital edema, age >3 years, and previous antibiotic therapy 2

Etiology and Pathophysiology

Orbital cellulitis is most commonly a complication of ethmoid sinusitis (45% of pediatric cases), with infection spreading through thin bony walls or valveless veins. 2, 3

Primary Sources of Infection:

• Paranasal sinusitis (most common, especially ethmoid) 2, 3
• Eyelid or facial infections 3, 4
• Retained foreign bodies 4
• Hematogenous spread from distant sites 3
• Trauma to the eyelids 5
• External ocular infection 5

Common Causative Organisms:

• Streptococcus pneumoniae 1, 2
• Haemophilus influenzae 1, 2
• Streptococcus pyogenes 1, 2
• Moraxella species 1, 2
• Anaerobic bacteria 1, 2
• MRSA (methicillin-resistant Staphylococcus aureus) in patients with risk factors 2

Diagnostic Evaluation

Immediate Imaging

CT orbits with IV contrast is the most useful initial imaging to differentiate preseptal from postseptal cellulitis, identify abscess formation, and detect life-threatening complications. 6, 2

CT Imaging Protocol:

• Obtain contrast-enhanced CT of orbits and paranasal sinuses immediately 6, 2
• CT is superior for detecting bone erosion, subperiosteal abscess, and osseous evaluation 6
• CT head with IV contrast should be added when intracranial complications are suspected (subdural empyema, cavernous sinus thrombosis) 2
• Use Chandler criteria to evaluate for bone erosion and subperiosteal abscess requiring surgical intervention 6

MRI Indications:

• MRI of brain with high-resolution images including cavernous sinuses provides superior soft-tissue resolution for detecting intracranial extension 6, 1
• Obtain MRI immediately if cavernous sinus thrombosis is suspected 1
• Contrast-enhanced MRI is preferred, but noncontrast MRI still provides useful information if contrast cannot be administered 6, 1
• Maintain high index of suspicion and low threshold for MRI if invasive fungal infection is suspected in immunocompromised patients 6
• CTA or MRA should be added if vascular invasion or cavernous sinus thrombosis is suspected, particularly in fungal disease 1

Laboratory Workup:

• Hemogram with differential 7
• Blood cultures before antibiotic initiation 1, 2
• C-reactive protein measurement 7
• Ionogram 7
• Search for soluble antigens in blood/urine 7

Clinical Assessment:

• Daily ophthalmologic examination to assess visual acuity, pupillary response, extraocular motility, and proptosis 1
• Evaluate for fever, headache, and systemic signs of infection 3, 4

Management Algorithm

Immediate Management (Within 1 Hour)

All patients with orbital cellulitis require immediate hospitalization with broad-spectrum IV antibiotics started within one hour of recognition. 1, 2

First-Line Empiric IV Antibiotic Regimens:

Vancomycin 15-20 mg/kg IV every 8-12 hours (for MRSA and streptococcal coverage) PLUS piperacillin-tazobactam 3.375-4.5 grams IV every 6 hours (for polymicrobial coverage including anaerobes and gram-negatives). 1

Alternative regimens include:

• Vancomycin PLUS meropenem 1 g IV every 8 hours 1
• Vancomycin PLUS ceftriaxone 2 g IV daily and metronidazole 500 mg IV every 8 hours 1
• High-dose amoxicillin-clavulanate IV with consideration for adding clindamycin for anaerobic coverage 2, 8

MRSA Coverage Considerations:

Add vancomycin to empiric regimens if risk factors for MRSA are present, including prior MRSA infection, nasal colonization, or injection drug use. 2

Surgical Intervention Criteria

Surgical drainage is indicated when orbital abscess is present on imaging, or if no clinical improvement occurs within 24-48 hours of IV antibiotics. 1

Urgent Surgical Indications:

• Progressive proptosis 1
• Worsening ophthalmoplegia 1
• Declining visual acuity 1
• Large subperiosteal abscesses 9
• Medial subperiosteal abscesses failing medical therapy (usually drained endoscopically) 9
• Lateral or intraconal abscesses (require open procedure) 9

Medical Trial Considerations:

• Children under 9 years respond to medical management more frequently than older patients 9
• Even children over 9 with small or moderate-sized abscesses and normal vision deserve a medical trial before surgical intervention 9

Treatment Duration and Transition

Continue IV antibiotics for 7-14 days, guided by clinical response, with reassessment at 5 days to determine if clinical improvement is occurring. 1

Transition to Oral Antibiotics:

• Transition to oral antibiotics once clinically improved, typically after 4-5 days of IV therapy 1
• Oral options include clindamycin 300-450 mg every 6 hours or linezolid 600 mg twice daily 1
• Amoxicillin-clavulanic acid for outpatient continuation 8, 7
• Complete 10-14 days of total antibiotic treatment 8

Multidisciplinary Consultation

Mandatory consultations include ophthalmology for monitoring visual function, otolaryngology for sinus source evaluation and surgical drainage, and infectious disease for antibiotic guidance. 1, 2

Ophthalmology Role:

• Monitor visual acuity, optic nerve function, and intraocular pressure 1
• Daily assessment of visual function and extraocular movements 2

Otolaryngology Role:

• Evaluate for sinus source 1
• Perform surgical drainage if indicated 1

Infectious Disease Role:

• Guide antibiotic selection, particularly if fungal infection is suspected in immunocompromised patients 1

Monitoring and Follow-Up

Daily ophthalmologic examination is mandatory to assess visual acuity, pupillary response, extraocular motility, and proptosis. 1

• Repeat imaging if clinical deterioration occurs or if no improvement within 48 hours 1
• Continuous in-house evaluation is necessary to observe for progression of symptoms 9
• Follow-up after discharge to ensure complete resolution and detect possible recurrences 8

Complications and Prognosis

Sight-Threatening Complications:

• Vision loss from optic nerve compression or ischemia 3, 4
• Permanent visual impairment if untreated 8

Life-Threatening Complications:

• Cavernous sinus thrombosis 2, 8
• Subdural empyema 2
• Brain abscess 8
• Meningitis 8, 4
• Superior ophthalmic vein thrombosis 2

Prognosis:

Morbidity and mortality associated with orbital cellulitis have declined significantly with advances in diagnostic imaging, antibiotic therapy, and surgical intervention when needed. 3 However, failing to recognize intracranial extension can result in cavernous sinus thrombosis, meningitis, brain abscess, or death. 2

Critical Pitfalls to Avoid

Delaying CT imaging when proptosis, visual changes, or ophthalmoplegia are present can lead to delayed diagnosis and treatment. 2

• Not considering MRSA coverage when risk factors are present leads to inadequate treatment 2
• Inadequate follow-up after initiating therapy, as failure to reassess within 24-48 hours can allow progression 2
• Failing to obtain MRI when intracranial extension is suspected 6, 1
• Treating orbital cellulitis as preseptal cellulitis with oral antibiotics only 2
• Delaying surgical intervention when abscess is present or medical therapy fails 1, 9

Special Considerations

Immunocompromised Patients:

Maintain high index of suspicion for invasive fungal infection in immunocompromised patients, as this carries significant morbidity. 6

Preseptal vs. Postseptal Distinction:

Preseptal cellulitis can be managed with outpatient oral antibiotics in mild cases (high-dose amoxicillin-clavulanate), while orbital cellulitis requires immediate hospitalization. 2, 8

Outpatient criteria for preseptal cellulitis include:

• Eyelid less than 50% closed 2
• No proptosis or visual changes 2
• No systemic signs of infection 2
• Reliable follow-up available 2
• Mandatory reassessment within 24-48 hours 2