A 46-year-old female patient presented with double vision and visual distortion.
Case History:
A 46-year-old female patient presented reporting a one week history if double vision and visual distortion. Two weeks prior to her visit the patient had fallen off her bicycle, hitting the right side of her head. At that time she seen at the local hospital A&E and was asymptomatic aside from headache. A CT scan performed in A & E demonstrated a small right zygomaticomalar fracture (Figure 1). The patient was discharged.
On examination at the presentation 2 weeks following the accident visual acuity was 6/6 OU. There was no anisocoria or relative afferent pupillary defect. Exophthalmometry measured 21 mm OD, 17 mm OS, base 95 mm. There was mild venous engorgement of the OD upper and lower eyelids and medial conjunctiva. Extraocular motility: displayed -3 abduction deficit OD (Figure 2). Intraocular pressure and dilated fundus examination were normal.
Figure 1: CT scan demonstrating a small right zygomaticomalar fracture
Figure 2: Extraocular motility: displayed -3 abduction deficit OD
WHAT IS YOUR DIFFERENTIAL DIAGNOSIS?
Differential diagnosis:
The differential diagnosis for new onset proptosis, venous engorgement and limitation of extraocular movements
• Dural Cavernous Fistula
• Thyroid Eye Disease
• Orbital Haemorrhage
• Orbital Varix
• Orbital Tumour
Clinical course:
A presumptive diagnosis of right-sided carotid cavernous fistula (CCF) was made based on clinical suspicion and the findings of proptosis, venous engorgement, and abduction deficit. The patient was sent for MRI/MRA imaging of the brain and orbit. The images demonstrated a right CCF as well as a markedly dilated right superior ophthalmic vein (Figures 3).
Figure 3: Markedly dilated right superior ophthalmic vein
Figure 4: Right CCF
The patient was urgently referred to Neurointerventional radiology. On angiography a high flow caroto-cavernous fistula (CCF) was noted. There was also extensive arterial damage to the right cavernous internal carotid artery (ICA) consistent with dissection.
As good flow was seen to cross a patent anterior communicating artery the fistula was treated with right internal carotid artery sacrifice, using coil embolisation (Figures 5 & 6). Fortunately, the right ophthalmic artery remained perfused via collateral circulation. After the procedure the patient had an unremarkable hospital course and she was discharged home six days later.
Figure 5: Intraoperative image demonstrating coil being deployed within the internal carotid system
Figure 6: Postoperative image showing coils within the internal carotid artery
Discussion:
A high flow caroto-cavernous fistula (CCF) is an abnormal communication between the venous cavernous sinus and the internal carotid artery. The fistula may occur spontaneously in the elderly or following some sort of head trauma, as in the case of our patient. In one retrospective study, the time to presentation following injury ranged from one day to as late as 2 years (1).
There are four distinct types of fistulas (types A-D). A type A fistula is a direct, high flow fistula between the cavernous internal carotid artery and the cavernous sinus. It is the most common CCF following head trauma. Direct fistulas are thought to form from a traumatic tear in the wall of the cavernous internal carotid artery or following rupture of an aneurysm. Thus high-pressure arterial blood gains rapid access to the venous system and leads to venous hypertension.
Type B-D, or indirect fistulas, occur between meningeal branches of the external or internal carotid artery and the cavernous sinus. These are low-flow fistulas. The aetiology of types B-D is unclear, but they have been associated with pregnancy, sinusitis, age, and trauma. Symptoms are usually mild and may include dilated conjunctival and episcleral vessels and mild proptosis. These low flow fistulas generally resolve without treatment.
The onset of symptoms with a Type A fistula is usually rapid and can be very dramatic. A triad of clinical findings has been described as exophthalmos, orbital bruit, and dilated conjunctival vessels. Clinical findings include venous congestion of the eyelids, conjunctiva and episcleral vessels, cranial nerve palsies (3, 4, or 6), visual loss, proptosis, elevated intraocular pressure, optic disc oedema, and dilated and tortuous retinal vessels.
Once a direct CCF is identified it is important to direct the patient to the appropriate treating specialist, either an interventional neurologist or neurosurgeon. Direct fistulas always require treatment. There are a variety treatment modalities, including transarterial or transvenous embolisation with coils, liquid embolic agents, balloon embolization, and stent placement (3-5). The success rate of closing the fistula with these treatments ranges from 55-99%. Potential complications of treatment include worsening of an oculomotor nerve palsy and loss of vision.
Take Home Points
• CCF can be classified as high flow or low flow
• In younger patients there is often a preceding history of head trauma
• Common findings include - exophthalmos, orbital bruit and dilated conjunctival vessels
• If a high flow CCF is suspected urgent referral to an interventional neuroradiologist should be arranged
References:
1.Brosnahan D, McFadzean RM, and Teasdale E. Neuro-ophthalmic features of carotid cavernous fistulas and their treatment by endoarterial balloon embolisation. Journal of Neurosurgery, Neurosurgery, and Psychiatry; 1992, Vol. 55:553-556.
2. Gemmete JJ, Ansari SA, Gandhi DM. Endovascular techniques for treatment of carotid-cavernous fistula. J Neuro-Ophthalmology. 2009, Vol 29: 62-71.
3. Uysal E, Kizilkili O, Ulusay M, Basak M. Endovascular trapping of direct carotid-cavernous fistula. J Clin Neurosci. 2010 Mar;17(3):392-4.
4. Wadlington VR, Terry JB. Endovascular therapy of traumatic carotid-cavernous fistulas. Crit Care Clin. 1999 Vol 15(4):831-54.