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Carotid-cavernous fistula

Opthalmologists Miss Claire Daniel and Miss Lucy Barker discuss a case and its management

The case

A 56-year-old man presents with a painful, red, ‘bulging' left eye and a droopy left upper lid. He'd had a road accident on a recent holiday, suffering multiple skull fractures and a subarachnoid

haemorrhage. His eye symptoms had developed since he returned and had got worse over the last six days.

On examination, his best-corrected visual acuity is 6/9 in each eye. He has a total ptosis on the left, and total ophthalmoplegia with no movement of the left eye. The right eye moves normally. His eye is red, with dilated, ‘corkscrew' episcleral vessels.

On referral, left proptosis is noted, and the intraocular pressure is elevated – at 31mmHg compared with 14mmHg on the right. There is no relative afferent pupillary defect, and fundal examination reveals engorged retinal vessels but no disc swelling.

His blood pressure is 138/84mmHg. CT imaging reveals a traumatic direct carotid-cavernous fistula (CCF). He is immediately referred to the nearest neurosurgical centre.

The problem

CCF is an abnormal arteriovenous communication between the carotid artery and the cavernous sinus. The venous pressure rises as the venous system becomes ‘arteriolised' and the venous flow rate and direction may be altered.

Direct CCF is more common and represents a direct communication between the intercavernous portion of the internal carotid artery and the cavernous sinus.  Around 75% of cases are due to head trauma – including surgery – with the remaining cases due to spontaneous rupture of an existing aneurysm or atherosclerotic vessel.1,2 

Indirect CCF – also known as dural shunts – represents a low-flow connection between the meningeal vessels of the internal or external carotid artery and the cavernous sinus.

Features

• Symptom onset is sudden for direct CCF.

• Symptoms are usually less severe and onset is gradual in indirect CCF.

• Symptoms include proptosis (which may be pulsatile), chemosis and engorged ‘corkscrew' episcleral vessels.

• Intraocular pressure is elevated – this may be palpable on digital examination.

• Visual loss may be a presenting feature, but is more often delayed in onset.

• Ophthalmoplegia and ptosis may be absent, partial or complete.

• Patients may hear a ‘whooshing' sound.

• Fundoscopy reveals dilated, engorged retinal vessels.

• Exposure keratopathy, retinal vein occlusion or optic disc swelling may develop if untreated.

• Spontaneous CCF, both direct and indirect, is most common in women and patients with hypertension.2

Differential diagnosis

• Thyroid eye disease – usually associated with a history of thyroid disease, although orbitopathy may be the presenting feature, with lid retraction and lid lag on down gaze

• Scleritis – severe pain, but no ophthalmoplegia

• Cavernous sinus thrombosis – usually associated with infection, headaches and signs of raised intracranial pressure, may spread to become bilateral

• Orbital cellulitis or abscess – febrile patient with signs of infection

• Orbital lesions – proptosis with less engorgement of episcleral vessels, will be non-pulsatile

Examination

• Check visual acuity.

• Check temperature and blood pressure.

• Check pupillary function and symmetry.

• Assess for proptosis – easily done from behind the patient looking over their head.

• Auscultate for orbital bruit.

• Assess ocular movements.

• Instil fluorescein to check for exposure keratopathy.

• Perform fundoscopy with direct ophthalmoscope if possible.

Referral

Refer urgently if there is any suspicion of CCF. Highlight any history of trauma, recent head and neck surgery, hypertension or thyroid disease in your referral.

Treatment

Topical ocular lubricants may be prescribed for immediate relief. The patient will be prescribed ocular antihypertensive medication to lower the intraocular pressure. Investigations include urgent orbital ultrasound, vascular sequence CT, MRI or digital subtraction angiography.

Urgent referral to a neurosurgical centre will be made for treatment with endovascular ablation, if appropriate. Treatment success rates are up to 99% for direct CCF and 78% for indirect CCF.3

Miss Claire Daniel is a consultant ophthalmic surgeon and Miss Lucy Barker is a specialist registrar at Moorfields Eye Hospital, London

References

1. de Keizer RJW. Carotid-cavernous and orbital arteriovenous fistulas: ocular features, diagnostic and haemodynamic considerations in relation to visual impairment and morbidity. Orbit 2003;22:121-42

2. Das JK, Medhi J, Bhattacharya P et al. Clinical spectrum of spontaneous carotid-cavernous fistula. Indian J Ophthalmol 2007;55:310-12

3 Gemmete JJ, Ansari SA and Gandhi DM. Endovascular techniques for treatment of carotid-cavernous fistula. J Neuro-Ophthalmol 2009;29:62-71

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