Infection · Hard
This case is fictional and exists for study. It describes no real patient.
42 years · female
A 42-year-old female presents to the emergency department with a 2-day history of rapidly progressive right eye pain, redness, and eyelid swelling. She reports having a severe nasal congestion and frontal headache over the preceding week. On clinical examination, the right upper and lower eyelids are tense, erythematous, and markedly oedematous. Examination of the right eye reveals obvious proptosis, reduced visual acuity (6/18 in the right eye, 6/6 in the left eye), and significant restriction of extraocular movements accompanied by severe pain on attempted gaze. Pupillary reflexes are intact bilaterally, and there is no papilledema. Systemic examination reveals fever and tachycardia.
Vital signs
- HR
- 112 bpm
- BP
- 118/76 mmHg
- RR
- 20/min
- Temp
- 38.8 °C
- SpO₂
- 97%
Examination findings
- Right eye proptosis and marked periorbital erythema/oedema
- Painful restriction of right extraocular movements
- Reduced right visual acuity (6/18)
- Intact direct and consensual pupillary light reflexes
Investigations
| Haemoglobin | 13.2 g/dL | reference: 12.0-15.5 |
| WBC | 17.4 10^9/L | reference: 4.0-11.0 |
| Platelets | 310 10^9/L | reference: 150-400 |
| C-reactive protein (CRP) | 156 mg/L | reference: 0-5 |
Question 1 of 3
Which of the following is the most likely diagnosis?
The clinical features of proptosis, painful restriction of extraocular movements (ophthalmoplegia), and impaired visual acuity indicate infection posterior to the orbital septum, confirming orbital cellulitis. Preseptal cellulitis involves tissues anterior to the septum and does not cause proptosis, pain with eye movements, or visual loss. Cavernous sinus thrombosis usually presents with rapid bilateral involvement, cranial nerve palsies (CN III, IV, V1/V2, VI), and papilledema. Thyroid eye disease is a chronic inflammatory disorder rather than an acute febrile infectious condition.
Teaching point: Proptosis, painful ophthalmoplegia, and decreased visual acuity distinguish orbital cellulitis from preseptal cellulitis.
Question 2 of 3
Which of the following is the next best diagnostic investigation to evaluate the extent of the condition?
A contrast-enhanced CT scan of the orbits and paranasal sinuses is the radiological investigation of choice. It confirms the diagnosis, evaluates sinus involvement, and detects complications such as subperiosteal or orbital abscess formation. MRI with contrast is sensitive for intracranial complications like cavernous sinus thrombosis but is usually second-line or reserved for specific neurological indications due to availability and acquisition time. Orbital ultrasound is limited in visualizing deep orbital structures. Plain radiographs cannot reliably differentiate orbital soft tissue structures.
Teaching point: Contrast-enhanced CT of the orbits and paranasal sinuses is the primary imaging modality to confirm orbital cellulitis and rule out intraorbital abscess.
Question 3 of 3
Which of the following is the single most appropriate initial management step?
Orbital cellulitis requires urgent hospital admission, immediate administration of high-dose intravenous broad-spectrum antibiotics (covering Streptococcus species, Staphylococcus aureus, and anaerobes), and emergency ophthalmology/ENT assessment. Oral antibiotics are insufficient and only appropriate for mild preseptal cellulitis. Bedside incision without prior imaging is hazardous and inappropriate. Corticosteroids alone without antibiotic coverage would exacerbate bacterial infection.
Teaching point: Orbital cellulitis requires immediate inpatient admission, empirical intravenous broad-spectrum antibiotics, and urgent specialist referral.
Key learning points
- Distinguish orbital cellulitis from preseptal cellulitis by checking for proptosis, painful eye movement, visual changes, and systemic symptoms.
- Contrast-enhanced CT of the orbits and paranasal sinuses is the definitive imaging investigation for suspected orbital cellulitis.
- Management of orbital cellulitis involves prompt hospital admission, intravenous broad-spectrum antimicrobial therapy, and urgent specialist multidisciplinary care.
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