Classified Eye Specialist, Military Hospital Rawalpindi.
SPONSOR / ACKNOWLEDGEMENT The study was self sponsored. We were thankful for the efforts of Dr Lubna Adeeb, Abrar CT and MRI Rawalpindi for her cooperation and efforts in making early diagnosis.
Proptosis due to carotid cavernous fistula is rare sequelae of head injury. We report a case of post traumatic, direct high flow cavernous fistula that resolved spontaneously 06 weeks after carotid angiography. It however resulted in loss of vision due to delay in early treatment. In all cases of post traumatic proptosis, carotid cavernous fistula should always be kept in mind.
INTRODUCTION Carotid–cavernous sinus fistulas (CCF) can result from head injury or may arise spontaneously. Post-traumatic cases account for about 75% of direct fistulas between the internal carotid artery and the cavernous sinus. These are often associated with fracture base of skull. [1-3] Spontaneous closure of CCFs by thrombosis of the cavernous sinus is uncommon, especially in the traumatic high flow type.  Cases of spontaneous occlusion of a traumatic CCF after orbital angiography have been reported.  We present the case of a patient who sustained a blunt head injury resulting in direct type carotid–cavernous sinus fistula which closes spontaneously without any intervention.
CASE REPORT Patient aged 37, presented on 7th May 2008 with history of head injury three weeks prior to presentation followed by bulging of her left eye, whooshing noises in her head and double vision. There was also history of ptosis of her left eye, swelling of both upper and lower lids on left side, left sided temporal headache and bleeding from left ear. There was no previous history of any ocular and systemic diseases.
Her general physical examination and systemic examination was unremarkable. Ophthalmic examination on presentation revealed corrected visual acuity of 20/30 in right and 20/40 in left. Her pupils were round but unequal in reaction in left eye as compared to right eye; rests of her optic nerve functions were unremarkable. There was severe ptosis in left eye. Adnexa showed swelling of both upper and lower lids with resistance to retropulsion. Conjunctiva showed chemosis and dilated episcleral blood vessels.
Her ocular movements were painful and limited in all directions of gaze. Forced duction test revealed restriction of all extra ocular muscles. She was having significant proptosis of 24mm with difference of 6mm from other eye. Fundus showed dilated veins with no haemorrhages or disc edema. Intraocular pressure was 38 mm of Hg with pulsating mires. Gonioscopy revealed open angle with no neovascularization. Ocular and cephalic bruits were audible. There was no increase in proptosis after Valsalva maneuver showing absence of venous anomalies in orbit.
On investigations there was fracture of petrous part of temporal bone on X Ray Skull lateral view. CT scan orbit axial view showed prominent superior ophthalmic vein and engorged extra ocular muscles on left side. Her Doppler ultrasound also revealed prominent superior ophthalmic vein on left side. Carotid arteriography revealed dilated cavernous sinus and arterialization of superior ophthalmic vein with retrograde flow. The contrast medium from internal carotid artery was seen filling the cavernous sinus through fistula and then flowing retrograde into the superior ophthalmic vein. Her CT Angiography also revealed dilated superior ophthalmic vein and enlarged cavernous sinus on left side (Figure-1 A-C).
On the basis of history, clinical examination and investigations a diagnosis of left traumatic direct high flow carotid cavernous fistula was made. She was treated with intraocular pressure lowering eye drops (Alphagan eye drops BD, Co-Dorzol eye drops BD), artificial tears, painkillers and intravenous antibiotics (injection Augmentin I/V 1.2 gm BD).
A treatment plan of endovascular approach for embolization of carotid cavernous fistula with balloon and coil was made. Due to financial constrains the patient managed the amount needed for intervention in about 06 weeks time. The condition of patient rapidly deteriorated before surgical intervention was made and she started losing her vision in left eye. Her proptosis had markedly increased. Her conjunctival congestion worsened. Her fundus with merely dilated veins developed marked hemorrhages and edema (Figure-2 A & C).
A few days before surgery it was noted that her chemosis started decreasing, proptosis reduced, intraocular pressure decreased, and ocular bruit stopped; whooshing noises were no more audible (Figure-2 B). A repeat CT angiogram also confirmed spontaneous closure (Figure-1 D). Her ocular movements started to regain and it was concluded that the fistula was closed spontaneously. But unfortunately she failed to regain her vision in left eye due to optic atrophy and vascular occlusion (Figure-2 D). She was advised not to take aspirin, warfarin, heparin or any other thrombolytic therapy lifelong by cardiologist.
DISCUSSION Carotid-cavernous fistula (CCF) is the most common arteriovenous malformation affecting the orbit. [6,7] Barrow et al. classified CCF into four arteriographic types with respect to communication between internal and external carotid arteries and their meningial branches with cavernous sinus and its tributaries. 
The cavernous sinuses are paired structures that lie within the sphenoid bone and communicate with each other via the circular sinus. The cavernous sinus contains a venous plexus that is part of the dural venous system, receiving blood from the sphenoparietal sinuses and the superior and inferior ophthalmic veins. There are a number of structures that pass through the sinus including the internal carotid artery and oculomotor, trochlear, trigeminal (ophthalmic and maxillary divisions) and abducens cranial nerves. 
Carotid-cavernous fistulas are broadly divided into two categories, direct and indirect. Head injury following road-traffic accidents, fights and falls account for approximately 75% of CCF. The injuries may be penetrating or non-penetrating and may be associated with basal or facial skull fracture.  Instances of direct CCF following surgical procedures (such as endoscopic nasal surgery, vascular, neurosurgery) or spontaneously from aneurysm ruptures have also been reported.
Endovascular approaches have been tried to correct high-flow post-traumatic CCF. [10-12] Spontaneous closure of CCFs by thrombosis of the cavernous sinus is uncommon, especially in the direct traumatic high flow type fistulas though it has been previously described.  As a mechanism of spontaneous occlusion, it is suggested that carotid angiography played an important role in most of these cases. They also suggested that stasis of the blood flow during venography may have caused the formation of a thrombosis inside of the cavernous sinus, which induced closure of the fistula.
In the case we have reported, the patient managed the expenses after about 06 weeks of diagnosis. Till then she lost vision in her left eye and her proptosis had markedly increased, but before surgery her fistula had closed spontaneously without any intervention. This is a quiet rarely reported event. The fistula was probably closed due to the formation of thrombus in cavernous sinus as reported by Alkhani et al  and it might be the result of carotid angiography performed 06 weeks earlier.
In the end we have concluded that though direct CCF is a rare complication of head injury, it must be kept in mind in all cases of post traumatic proptosis. Early diagnosis and prompt intervention will not only save the eye but also the life of patient which is always at risk due to intracerebral bleed secondary to rupture of dilated cavernous sinus.