The Ophthalmology Department,  Universiti Malaysia Sarawak (UNIMAS), Kuching, Sarawak.

The Ophthalmology Department, Sarawak General Hospital, Kuching, Sarawak, East Malaysia.

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Case 42a

by Dr. Tan Aik Kah, Dr. Ngo Chek Tung and Professor Chua Chung Nen

 

A 35 year-old man was assaulted 4 weeks ago with a blunt object over his right temporal region. At the time of the injury, there was no loss of consciousness or ocular injury. However, over the next few weeks, he exprienced progressive swelling and redness of the right eye. There was no medical history of note.

 

On examination, the right eye (Figure 1 and 2) was noted to be red with moderate non-axial proptosis (confirmed on Hertel's exophthalmometer and measured 20mm in the right eye and 15 mm in the left eye). The right conjunctiva  showed dilated vessels (Figure 3). The visual acuity measured 6/12 in the right eye and 6/6 in the left eye. The intraocular pressures measured 40 in the right eye and 18 in the left eye. Gonioscopy showed blood in the right trabecular meshwork (Figure 4). Fundoscopy showed no optic disc or retina abnormalities. The proptosis is non-tender to palpation. Bruit can be heard with the bell of a stethoscope when the eye was closed.

 

Figure 1. Side view showing right proptosis and dilated conjunctival vessels.

 

Figure 2. Frontal view showing right non-axial proptosis.

 

Figure 3. Dilated cork-screw vessels.

 

Figure 4. Blood in the trabecular meshwork. The trabecular meshwork appears less brown than

normal because of the blood.

 

He was started on topical latanoprost and timolol but the pressure remained high at 35mmHg. Oral acetazolamide 500mg b.d. was added and this brought the pressure down to 25mmHg. CT angiograms were as shown below (Figure 4 and 5) and the patient was referred to the neurosurgeon for co-management.

 

Figure 5. Axial CT angiogram view of the orbit and brain.

 

Figure 6. Saggital CT angiogram.

 

a. What do the CT angiograms show? What is the most likely diagnosis?

 

The axial scan shows dilated superior ophthalmic vein indicating raised cavernous sinus pressure. The superior ophthalmic vein also contains strong enhancement similar in intensity to the internal carotid artery suggesting communication between the internal carotid artery and the cavernous sinus and the superior ophthalmic vein. The saggital view shows dilated superior ophthalmic vein having the same enhancement as the internal carotid artery.

 

Direct carotid-cavernous fistula secondary to blunt trauma is the most likely diagnosis. Cerebral angiogram is the gold standard for confirming the diagnosis. The patient will undergo the investigation under neurosurgical supervision.

 

Carotid-cavernous fistula (CCF) can be classified into 4 types using Barrow's classification1:

  • Type A: Direct CCF shunts between cavernous portion of the internal carotid artery.

(Type B-D indirect CCF (dural fistulae btw cavernous sinus and extradural branches of internal carotid artery, external carotid artery, or both.)

  • Type B: between meningeal branches of internal carotid artery and cavernous sinus.

  • Type C: between meningeal branches of external carotid artery and cavernous sinus.

  • Type D: between meningeal branches of both internal carotid artery and external carotid artery and cavernous sinus.

 

b. What are the mechanisms of raised intraocular pressure in this condition?

 

There are two mechanisms for raised intraocular pressure in CCF2:

 

i. Open-angle mechanism: This is the most common mechanism. The outflow facility is disturbed due to elevation of the episcleral venous pressure. Gonioscopy will reveal blood in the trabecular meshwork. 

ii. Closed-angle mechanism. This may be due to two events:

a. Elevated venous pressure causes congestion and oedema of choroid and ciliary body, producing forward displacement of lens-iris diaphragm & a shallow anterior chamber.

 

b. CCF may lead to the development of neovascular glaucoma due to ischemia through obstruction of venous blood flow.
 

c. What are the treatment modalities for this condition?

 

Direct CCF used to be managed by two basic approaches: The carotid occlusion or the carotid preservation techniques3, 4.

 

In the carotid occlusion technique, the internal carotid artery is tied to stop the blood flow through the fistula. This is now rarely performed due to the high risk of cerebrovascular accident.

 

The carotid preservation technique or endovascular technique involves direct closure of the fistula and involves interventional radiology. There are three ways of closing the fistula:

i.  embolization of the cavernous sinus (Figure 7),

ii. balloon occlusion of the fistula (Figure 8),

iii. insertion of coil in the part of the internal carotid artery with fistula

  

   Figure 7. Embolization of the cavernous sinus to close a direct CCF. The catheter was introduced through the

               superior ophthalmic vein (left). The right picture shows closure of the fistula.

Figure 8. Diagrams showing the steps involved in balloon closure of the fistula

via the internal carotid artery.

 

d. What is the natural history of this condition?

 

Without treatment, patients with a direct carotid-cavernous sinus fistula experience progressive ocular complications. These complications include progressive proptosis, conjunctival chemosis, and visual loss occur over months to years. The visual loss usually results from either central retinal vein occlusion or secondary glaucoma5.

 

In addition to ocular problem, cerebral haemorrhage is an important cause of morbidity and mortality. A 3% incidence of spontaneous intracerebral hemorrhage caused by carotid-cavernous sinus fistulae has been reported.

 

If successfully treated, symptoms and signs improve within hours to days. The rate and extent of improvement are associated with the severity of the signs and the length of time the fistula was present.Ocular bruit, ocular pulsations, & thrill generally disappear immediately after the surgery. Eyelid engorgement, conjunctival chemosis, dilated conjunctival vessels, stasis retinopathy, disc swelling, and elevated intraocular pressure generally return to normal within weeks to months.
 

Reference:

1. Barrow DL, Spector RH, Braun IF, et al: Classification and treatment of spontaneous carotid-cavernous sinus fistulas. J Neurosurg 1985 Feb; 62(2): 248-56.

 

2. Ishijima K, Kashiwagi K, Nakano K, Shibuya T, Tsumura T, Tsukahara S. Ocular manifestations and prognosis of secondary glaucoma in patients with carotid-cavernous fistula. Jpn J Ophthalmol. 2003 Nov-Dec;47(6):603-8.
 

3. Wadlington VR, Terry JB: Endovascular therapy of traumatic carotid-cavernous fistulas. Crit Care Clin 1999 Oct; 15(4): 831-54, viii.

 

4. Fattahi, T., Brandt, M., Jenkins, W., & Steinberg, B. (2003). Traumatic carotid-cavernous fistula: Pathophysiology and treatment. Journal of Craniofacial Surgery, 14, 240–246.

 

 

5. Phatouros CC, Meyers PM, Dowd CF, et al: Carotid artery cavernous fistulas. Neurosurg Clin N Am 2000 Jan; 11(1): 67-84, viii.