The complementary image.

Case

A 30-year-old male presented with history of complete loss of vision and protrusion of the right eye following a road traffic accident 2 weeks back. The protrusion was progressive and associated with pain. On examination, the right eye had no perception of light. There was proptosis of around 4 mm with chemosis of conjunctiva and the extraocular movements were completely restricted in all direction of gazes [Fig. 1a]. Exposure keratopathy precluded a fundus evaluation, and no thrill or bruit was noted. The left eye was otherwise normal. Patient had already got a computed tomography (CT) scan done which was suggestive of diffuse right-sided orbital edema, thickened extraocular muscles, and fracture floor of right orbit along with fracture of right frontal sinus. [Fig. 1b] Patient was diagnosed with posttraumatic orbital cellulitis elsewhere and was advised systemic antibiotics. Patient however did not follow the advice and consulted us for a second opinion.

Figure 1

(a) External colored clinical photograph of the patient showing right-sided proptosis, chemosis, and exposure keratopathy. Patient had restricted extraocular motility in all direction of gazes. (b) CT scan, axial cut showing right diffuse orbital edema with enlarged medial and lateral recti (arrows). The superior ophthalmic vein and cavernous sinus cannot be commented upon. (c) MRI scan, T2-weighted axial cuts showing right periorbital edema, engorged and prominent superior ophthalmic vein (small arrow). The cavernous sinus is distended with altered signal intensity (bigger arrow)

What is your Next Step?

Urgent intravenous methylprednisolone (IVMP)

Administer intravenous antibiotics covering anaerobes

Exploratory surgery and fracture repair with repositioning of the orbital contents

Magnetic resonance imaging (MRI) of brain and orbit.

Findings

The patient was advised to undergo an MRI brain and orbit. MRI revealed diffuse right orbital edema along with enlarged and thickened extraocular muscles. The superior ophthalmic vein (SOV) was prominent and engorged [Fig. 1c]. The right cavernous sinus was enlarged with increased vascularity [Fig. 1c]. An abnormal communication was noted between right internal carotid artery and the cavernous sinus on angiography. The findings were suggestive of posttraumatic right-sided carotid cavernous fistula (CCF). The patient was referred to an interventional radiologist for digital subtraction angiography (DSA) for confirming the type of fistula and further management.

Diagnosis

Right CCF

Discussion

Carotid-cavernous fistula results from an abnormal communication between the arterial and venous systems within the cavernous sinus. It is a type of arteriovenous fistula and most commonly results from trauma.

CT scan is the modality of choice in evaluation of orbital trauma.[1] Bony fractures and displacements, small comminuted fragments, and radiopaque foreign bodies are best visualized on CT scan. In this particular case though the typical thrill present in most cases of CCF was absent, enlarged extraocular muscles along with other clinical features raised sufficient doubts.

Carotid-cavernous fistulae may either occur spontaneously or follow trauma. Imaging characteristically demonstrates filling defects within the superior ophthalmic vein, often with associated enlargement of both the superior ophthalmic vein and the cavernous sinus, engorgement of the extraocular muscles, exophthalmos, and periorbital edema.[2] Prominent SOV, which is an important radiological feature of CCF can be made out in CT scan, but because of the poor scan quality the same could not be commented upon. The dilemma lead us to order an MRI that would depict all the soft tissue findings very clearly. DSA is considered the gold standard investigation whilst offering the possibility of endovascular treatment.[2] Treatment varies according to the etiology and velocity of flow across the fistula.

CT scan is the imaging modality of choice in setting of acute trauma. However in select cases where the CT scan findings do not correlate with the clinical presentation or show some unusual findings; enlarged extraocular muscles (EOM) in the present case, an MRI should necessarily be ordered. In such cases, both CT and MRI are complementary to each other.[3] Both CT and MRI have their own advantages and pitfalls. The protocols should be planned as per clinical indication.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.