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