Figure 1

Figure 2

Figure 3

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This 65 year old woman presented to the eye casualty with a one week history of diplopia. Ocular motility examination revealed limited left eye movement in all direction and the orthoptic examination revealed a left sixth nerve palsy and partial third nerve palsy without pupil involvement. Her visual acuities in both eyes were normal and the fundoscopy was unremarkable. An urgent CT scan was requested.

a. What does the CT scan show?

The CT scan shows enlargement of the left superior ophthalmic vein (figure 1) compared with that of the right superior ophthalmic vein (figure 2). This suggests an increased pressure in the cavernous sinus.
 

b. What is the most likely diagnosis?

Enlarge superior ophthalmic vein is a feature of carotid-cavernous fistula. This is demonstrated in Figure 3 with internal carotid artery angiography showing leakage of dye from the left internal carotid artery.
 

c. How would you manage this condition?

The absence of proptosis and trauma suggest it is a low flow fistula. This usually results from a connection between the meningeal branches of the internal carotid artery and the cavernous sinus (dural fistula). The condition typically occurs in post-menopausal women and there is usually a medical history of hypertension or arteriosclerosis.
Most cases of low flow fistula close spontaneously and no surgical intervention is required. Compared this with  high flow fistulas which is commonly associated with trauma and require surgical intervention such as intravascular embolisation with particles such as poly-vinyl alcohol or intravascular balloon.
 
 
 

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