Ethmoid Sinusitis

Ethmoid sinusitis is infection of the ethmoid air cells, which are present from birth and are the usual source of orbital complications of sinusitis in children. The thin lamina papyracea separates them from the orbit.

It is the commonest sinus to be infected in children under 5 years. Orbital complications occur in a small share of acute sinusitis, and the Chandler classification grades them: preseptal cellulitis, orbital cellulitis, subperiosteal abscess, orbital abscess and cavernous sinus thrombosis. Common organisms are Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus and anaerobes.

Pathophysiology.

Obstruction of the narrow ethmoid ostia traps secretions. Infection spreads through the thin lamina papyracea, dehiscences and valveless ethmoid veins into the orbit.

Pain between and behind the eyes, nasal blockage, purulent discharge, loss of smell and fever. Eyelid swelling, redness, chemosis, proptosis, painful or limited eye movement, and reduced vision indicate orbital extension.

Red flags.

• Proptosis, ophthalmoplegia or painful eye movement.
• Reduced visual acuity or colour vision, or a relative afferent pupillary defect.
• Severe headache, neck stiffness or confusion.
• Bilateral eye signs (cavernous sinus thrombosis).

Clinical examination with assessment of vision, pupils and eye movements. CT of the orbits and sinuses with contrast is done when orbital signs are present, to identify abscess. Magnetic resonance imaging is done for intracranial extension. Send blood cultures, full blood count and C-reactive protein, and nasal swab culture.

Differential diagnosis.

• Preseptal cellulitis from skin infection.
• Allergic or viral rhinosinusitis.
• Orbital tumour or rhabdomyosarcoma in children.
• Thyroid eye disease.
• Dacryocystitis.
• Cavernous sinus thrombosis.

Mild uncomplicated disease is treated with oral antibiotics, decongestants and nasal steroids. Orbital cellulitis needs admission, intravenous antibiotics and urgent ophthalmology and ENT review. Drain a subperiosteal or orbital abscess when there is reduced vision, a large abscess (over 10 mm), intracranial extension, or failure to improve in 24 to 48 hours.

• Co-amoxiclav (uncomplicated): 625 mg orally three times daily for 10 to 14 days; maximum 1.5 g amoxicillin daily; monitor liver tests, diarrhoea and rash; give 625 mg twice daily when creatinine clearance is 10 to 30 mL/min; children 25 mg/kg amoxicillin twice daily.
• Ceftriaxone (orbital or complicated): 2 g IV once daily (children 50 to 100 mg/kg daily, maximum 4 g); maximum 4 g daily; usually 7 to 14 days then oral step down to complete 2 to 3 weeks; monitor renal function, liver tests and blood counts.
• Metronidazole (with ceftriaxone): 500 mg IV or orally every 8 hours (children 7.5 mg/kg every 8 hours); maximum 1.5 g daily; monitor neuropathy and liver tests; reduce to 500 mg every 12 hours in severe hepatic impairment.
• Vancomycin (added for suspected MRSA): load 25 to 30 mg/kg IV, then 15 to 20 mg/kg every 8 to 12 hours; target area under the curve 400 to 600; monitor levels and creatinine.

Monitoring. Visual acuity, pupils and eye movements every 4 hours in orbital disease; repeat imaging when there is no improvement.

Referral and escalation. ENT and ophthalmology urgently; paediatrics for children.

Special groups. Children under 5 years need weight based dosing and a low threshold for CT.