Sphenoid Sinusitis

Sphenoid sinusitis is inflammation of the sphenoid sinus, either isolated or with other sinuses (pansinusitis). It is uncommon but dangerous because of the adjacent optic nerve, cavernous sinus, internal carotid artery and pituitary.

Isolated disease makes up 1% to 3% of sinusitis. It is diagnosed late. Complications arise in up to 40% of cases when it is not treated promptly: cavernous sinus thrombosis, meningitis, brain abscess, optic neuritis, and cranial nerve palsies. Organisms are Staphylococcus aureus, streptococci and anaerobes, with fungi in immunocompromised patients.

Pathophysiology.

Obstruction of the sphenoethmoidal recess traps secretions in the sinus. The thin bony walls, dehiscent in places, and the venous connections to the cavernous sinus allow spread of infection.

Headache (deep, vertex, frontal or retro orbital, worse lying down), fever, postnasal discharge, and sometimes visual disturbance, double vision, facial numbness or proptosis. Nasal symptoms are often minimal.

Red flags.

• Visual loss, double vision or ophthalmoplegia.
• Severe headache with fever, neck stiffness or confusion.
• Proptosis or chemosis.
• Cranial nerve palsy.

Nasal endoscopy shows pus at the sphenoethmoidal recess. CT of the sinuses and skull base shows opacification of the sphenoid, air fluid level and bone erosion. Magnetic resonance imaging with contrast and venography is done for suspected intracranial complications. Send blood cultures, and swab culture at endoscopy. Lumbar puncture is done only after imaging when meningitis is suspected.

Differential diagnosis.

• Sphenoid mucocele or pyocoele.
• Fungal ball and invasive fungal sinusitis.
• Pituitary apoplexy or abscess.
• Sphenoid malignancy.
• Migraine and cluster headache.
• Cavernous sinus thrombosis.

Uncomplicated disease is treated with antibiotics, decongestant and steroid spray, while complicated disease or failure to improve in 48 to 72 hours needs intravenous antibiotics and urgent endoscopic sphenoidotomy.

• Co-amoxiclav (uncomplicated, outpatient): 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.
• Ceftriaxone (complicated): 2 g IV every 12 hours; maximum 4 g daily; usually 2 to 6 weeks, depending on complications; monitor renal function, liver tests and blood counts; no routine renal adjustment.
• Metronidazole (with ceftriaxone): 500 mg IV or orally 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; extend the interval in renal impairment.

Anticoagulation is considered for cavernous sinus thrombosis by specialist decision. Dexamethasone 10 mg IV every 6 hours for 4 days is given for meningitis, started before or with the first antibiotic dose.

Monitoring. Visual acuity, eye movements and neurology every 4 to 6 hours in complicated disease; repeat imaging at 1 to 2 weeks.

Referral and escalation. ENT, neurosurgery and ophthalmology urgently.

Special groups. Children need weight based dosing: ceftriaxone 100 mg/kg daily (maximum 4 g).