Cavernous Sinus Syndrome and Orbital Apex Lesions
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Direct answer
Cavernous sinus syndrome is a combination of ophthalmoplegia, facial sensory loss and sometimes Horner syndrome, caused by a lesion within the cavernous sinus beside the sella turcica. The third, fourth, sixth and first two trigeminal nerves pass through it, so the pattern of deficits depends on which of them are involved. Septic thrombosis, pituitary tumours and carotid-cavernous fistula are the causes that most often need urgent action.
What you must remember
- Nerves involved: cranial nerves III, IV, V1, V2 and VI, with the internal carotid artery and its sympathetic plexus running through the sinus.
- Vision spared: the optic nerve passes above the sinus in the optic canal, so visual loss argues for the orbital apex or a more posterior lesion.
- Abducens palsy: the sixth nerve lies lateral to the internal carotid artery within the sinus and is a frequent early palsy.
- Horner syndrome: ptosis and miosis result when sympathetic fibres travelling along the internal carotid artery are damaged; facial anhidrosis is usually absent because sudomotor fibres follow the external carotid.
- Septic thrombosis: spreads from the danger triangle of the face through facial veins, is often caused by Staphylococcus aureus, and is frequently bilateral through the intercavernous sinuses.
- Carotid-cavernous fistula: pulsatile proptosis, chemosis, a bruit and raised intraocular pressure, confirmed by CT angiography or digital subtraction angiography.
- Tolosa-Hunt syndrome: painful ophthalmoplegia from idiopathic granulomatous inflammation, a diagnosis of exclusion that responds to corticosteroids.
- Orbital apex syndrome: adds the optic nerve to the picture, so visual loss and total ophthalmoplegia appear together.
An approach from the bedside to the scan
The approach starts with the examination and ends with imaging. Each step narrows the cause before the scan is chosen.
- Map the deficits: Note which of III, IV, V1, V2 and VI are affected, and check for Horner syndrome. Any loss of vision means the optic nerve is involved, which points towards the orbital apex.
- Examine the eye: Look for proptosis, chemosis and a bruit. Pulsatile proptosis with raised intraocular pressure points to a carotid-cavernous fistula.
- Look for infection: Fever, headache and a facial or sinus source suggest septic thrombosis, particularly when signs are bilateral.
- Image the sinus: MRI with MR venography or CT venography assesses thrombosis, and CT angiography or digital subtraction angiography confirms a fistula.
- Search for a mass: Pituitary macroadenoma, meningioma, nasopharyngeal carcinoma and lymphoma are looked for on contrast MRI, with biopsy where needed.
- Make the exclusion diagnosis: Tolosa-Hunt syndrome is considered only after other causes are ruled out, and a response to corticosteroids supports it.
Where the examiner tests the sinus
Questions often describe a painful eye or a double vision case and ask for the most likely cause.
- Trap: Including optic nerve involvement in cavernous sinus syndrome. Correct: Vision is spared in cavernous sinus lesions because the optic nerve lies above the sinus, so visual loss points to the orbital apex.
- Trap: Treating septic thrombosis as a simple sinus infection. Correct: It needs urgent intravenous antibiotics and imaging, since it can spread to the opposite sinus and to the meninges.
- Trap: Diagnosing Tolosa-Hunt syndrome without imaging. Correct: It is a diagnosis of exclusion, made only after MRI and other causes such as tumour or infection are excluded.
- Trap: Missing a carotid fistula in a red, painful eye. Correct: Pulsatile proptosis with a bruit is a fistula until proved otherwise, and it needs urgent angiography.
Frequently asked questions
Which cranial nerves pass through the cavernous sinus?
The third, fourth, sixth and the first two divisions of the trigeminal nerve pass through the cavernous sinus, alongside the internal carotid artery. The optic nerve does not pass through it, which is why vision is usually spared in a cavernous sinus lesion.
Why is vision spared in cavernous sinus syndrome?
Vision is spared in cavernous sinus syndrome because the optic nerve runs above the sinus through the optic canal, not within it. Loss of vision therefore suggests that the lesion has extended to the orbital apex, where the optic nerve is also affected.
What are the features of a carotid-cavernous fistula?
A carotid-cavernous fistula presents with pulsatile proptosis, chemosis, a bruit and raised intraocular pressure. Dilated episcleral veins and a red eye are typical, and the fistula may follow head injury or arise spontaneously. Diagnosis uses CT angiography or digital subtraction angiography, and endovascular embolisation is the usual treatment.
Why is septic cavernous sinus thrombosis dangerous?
Septic cavernous sinus thrombosis is dangerous because infection can spread to the opposite sinus through the intercavernous sinuses and into the meninges. Its classic source is the danger triangle of the face, where facial veins drain into the sinus. Fever, proptosis and multiple cranial nerve palsies call for urgent intravenous antibiotics and imaging.