Bulging red eye - post traumatic or spontaneous

Dr Harsh Rastogi

Rajan met with a road traffic accident two months back. He was unconscious for a few minutes, had a black eye on the right side, cut over the fore head which was sutured at a prestigious Hospital in Jaipur. Rajan has recovered almost completely over the past six weeks but now complains of blurring of vision and a very annoying persistent humming noise in his right ear. At the first sight he appears normal, but on a closer look anyone can make out that he has a bulging red eye on the right side. Rajan is suffering from a condition called post traumatic carotico cavernous fistula (CCF).

The fairy red eye resembles “conjunctivitis” and “inflammation” that does not respond to conventional therapy. Except that it involves usually one eye. Practitioners in virtually every medical specialty will misdiagnose the first case of CCF that they encounter. His is not a life threatening condition but needs urgent medical attention to prevent loss of vision. These patients usually have raised intra ocular pressure; unilateral red eye with raised intra-ocular pressure should clinch the diagnosis.

Two distinct types of patients develop carotid-cavernous fistula (CCF). The first is the patient who suffers significant head trauma, often from a traffic accident. This is seen in patients of all age, race and sex profiles. The second is the patient who develops a CCF spontaneously. This patient is typically a middle-aged female, often with concurrent hypertension.

Patients who develop a CCF traumatically have pronounced symptoms and signs. There will be marked congestion of the eyelids, conjunctiva and orbit. There is typically bulging eye and limitation of ocular movement. Also, the patient will experience vision loss from a host of possible causes, including secondary glaucoma, exposure keratopathy, and retinal and optic nerve ischemia. The patient may experience double vision and restricted eye movement, humming in the ears or orbital bruit, and a red, congested eye that is often mistreated as an ocular infection or inflammation. Intraocular pressure is often elevated in the involved eye. The signs and symptoms of a spontaneous CCF—also known as a low-flow fistula or dural sinus fistula—are similar to the trauma-induced disorder, albeit much less pronounced.

Pathophysiology

CCF is a specific type of fistula characterised by abnormal arteriovenous shunting within the cavernous sinus. The cavernous sinus is a trabeculated venous cavern on each side of the sphenoid bone. It receives blood from the eye via the superior and inferior ophthalmic veins.

Post traumatic CCF occurs when there is a rupture within the cavernous sinus of either the internal carotid artery (ICA) resulting in the mixing of high-pressure arterial blood into the low-pressure venous system results in the ocular congestion and conjunctival arterialisation as blood flows retrograde to the eye and adnexa. Rupture of the ICA itself is typically due to trauma, and the signs and symptoms are pronounced. Rupture of one of the smaller branches is typically spontaneous, with milder signs and symptoms.

This mixing of high-pressure blood in a low-pressure venous system. While typically unilateral, the presence of an intercavernous sinus allows for possible bilateral involvement.

The mixing of arterial blood in the venous system can allow the patient to hear his or her own heartbeat. You may hear this orbital bruit by placing a stethoscope over the patient’s eye. Secondary glaucoma develops frequently.

In some cases, excess blood from the ruptured blood vessel is rerouted through veins of the brain; this imparts a high-risk situation, as the patient can now possibly develop a fatal brain hemorrhage.

Management

Diagnosis of CCF is accomplished through neuroimaging and arteriography. Contrast-enhanced CT scan and MRI will demonstrate a dilated superior ophthalmic vein and cavernous sinus. Catheter Angiography for the brain vessels is still the gold standard in identifying CCF with vessel involvement.

CCF resulting from intracavernous rupture of the ICA or its branches requires endovascular treatment done by interventional radiologists and neuroradiologists. These specialists insert thin tubes (micro catheter) in the blood vessels of the brain to occlude the fistula. Current micro catheter techniques permit access to the cavernous sinus via several routes. The most common involves inserting a catheter through the femoral vein and gaining arterial or Tran venous access via the inferior petrosal sinus. The neuro-interventionists repairs the fistula by occluding the rupture with a detachable balloon, liquid adhesive, polyvinyl alcohol particles or endovascular metallic coils.

The main ocular concern in CCF is the development of secondary glaucoma. This may be difficult to treat because most glaucoma medications only reduce the gap between intraocular pressure and episcleral venous pressure. As the episcleral venous pressure elevates in CCF, it is very difficult to reduce IOP medically. Prostaglandin-like medications can reduce IOP without involving the episcleral venous system, so these are probably most indicated to manage this type of glaucoma.

Trans-arterial or trans-venous endovascular therapy is a low-risk treatment that is successful in 90 per cent of all CCF cases. This is minimally invasive and is done by specialists radiologists trained in intervention.

The writer is managing director, Radiodiagnosis, Indraprastha Apollo Hospitals, New Delhi