Carotid-cavernous fistula (CCF) is the most common arteriovenous malformation (AVM) affecting the orbit.12 Case reports of dural arteriovenous fistula were first published in the 1930s. Though the clinical presentation was appreciated the pathophysiology was not well understood at that time. It was only in the 1970s and 1980s that the anatomy was further described. In 1985, Barrow et al. classified CCF into four arteriographic types with respect to communication.3
Carotid-cavernous fistula is broadly divided into two categories, direct and indirect. Head injury following road-traffic accidents, fights and falls account for approximately 75% of CCFs.23 The injuries may be penetrating or non-penetrating and may be associated with basal or facial skull fracture.4 Instances of direct CCF following surgical procedures (such as endoscopic nasal surgery, vascular, neurosurgery) or spontaneously from aneurysm rupture have also been reported.5
Spontaneous shunts occur between the cavernous sinus and one or more meningeal branches of the internal carotid artery (ICA), the external carotid artery (ECA) or both. Approximately 25% of the CCF is of the spontaneous variety. The meningohypophyseal trunk and the artery of the inferior cavernous sinus provide the arterial supply to most dural shunts.2 Such shunts may follow expansion of congenital AVM or secondary to spontaneous rupture of one of the thin-walled dural arteries passing through the sinus.6 We report three cases of spontaneous CCF without any collagen vascular disease.
A 45-year-old lady presented with severe proptosis, gross dimness of vision and pain in the left eye with headache for the last four weeks. She was treated elsewhere with systemic steroids for pseudotumor. History disclosed a throbbing type of headache followed by gradual gross proptosis of the left eye. She was a known diabetic for the last two years and on systemic examination was found to be hypertensive with systemic blood pressure of 130/86 mmHg (under medication). Ocular examination showed a visual acuity of hand movement close to face (HMCF), gross axial, non-pulsatile proptosis, severe chemosis of the conjunctiva and III, IV, VI cranial nerve palsies leading to restriction of extraocular movement. Other parameters were within normal limits. Computerized tomography (CT) scan of the orbit showed enlarged cavernous sinus and dilated superior ophthalmic vein [Fig. 1]. The mode of presentation, physical examination and radiological findings suggested the diagnosis of CCF. The magnetic resonance angiography (MRA) showed a Type 1 CCF of the left side [Fig. 2]. The patient was advised embolization, which she declined due to financial constraints and did not return to the clinic.
A 57-year-old lady presented with complaints of headache, diplopia and diminution of vision, with gradual proptosis and mild restricted movement of both eyes for the past six weeks. The patient was diagnosed elsewhere as glaucoma with bilateral lateral rectus palsy. On examination the best corrected visual acuity (BCVA) was 20/20, N6 in both the eyes. Applanation tonometry showed a raised intraocular pressure (IOP) (right eye - 30 mmHg, left eye- 26 mmHg). The pupil showed a sluggish reaction to light. Extraocular motility revealed bilateral lateral rectus paresis. There was episcleral venous congestion [Fig. 3] and exophthalmometry showed 2 mm proptosis that was compressible and the bruit and pulsatility disappeared on compression over the ipsilateral carotid artery. Systemic examination showed a blood pressure of 170/98 mmHg with a positive family history of hypertension, but no evidence of collagen vascular disease was present. Definitive diagnosis was arrived at after MRA, which revealed a bilateral indirect CCF. To treat the secondary glaucoma and restriction of ocular movements, she was advised embolization under the care of an interventional radiologist [Fig. 4]. The patient underwent trans-cutaneous embolization of CCF with left cavernous sinus packing with coil. Eight months after embolization, the patient presented with a BCVA of 20/20 in both eyes, normal IOP and resolution of all signs and symptoms.
A 20-year-old lady presented with redness, discomfort and mild proptosis since eight weeks in the right eye. Visual acuity was 20/20 at presentation, with full ocular movements, brisk pupillary reflex to light, IOP of 16 mmHg in the right eye and 14 mmHg in the left eye and normal fundus. Presence of episcleral venous congestion, minimal proptosis and bruit on auscultation was detected. Systemic examination showed elevated systemic blood pressure of 200/108 mmHg and a positive family history of hypertension. Neurological examination and magnetic resonance imaging (MRI) impression was suggestive of a right-sided carotid cavernous dural fistula. Color Doppler confirmed the same showing low impedance flow in right ICA.
A high index of suspicion is the key factor in diagnosing a case of CCF without any history of trauma and collagen vascular disease. Delay in diagnosis or misdiagnosis is always a possibility unless patients without classical presentation are not critically evaluated. This series has a case of bilaterally raised IOP being treated elsewhere as glaucoma. Innocuous signs like epibulbar venous dilatation and barely perceptible proptosis should raise the alarm [Fig. 3].
The diagnosis is usually based on clinical manifestations and radiological evaluation. Patients suspected of having cavernous sinus lesions should undergo thin section, multiplanar imaging studies of the orbit and the parasellar region. The CT and MRI study helps in detecting proptosis, increased extraocular muscle size, dilated or thrombosed superior ophthalmic vein. An engorged superior ophthalmic vein presents with a characteristic "hockey stick sign" on orbital ultrasound, CT and MRI.2 Pre and post-contrast scans may suggest a distended cavernous sinus and rule out other causes of ocular manifestations.
Arriving at a diagnosis of direct CCF, especially in posttraumatic cases is relatively easy from the history and clinical presentation. However, the same may not be true in case of the spontaneous variety. The indirect variety may be mistaken for chronic conjunctivitis, orbital pseudotumor, orbital cellulitis or thyroid disease.6 Diagnosing such cases requires meticulous clinical and radiological evaluation and a high index of suspicion. Treatment is usually tailor-made. All cases of direct CCF call for interventional treatment. Only selected symptomatic cases of the indirect variety need to be treated. Embolization is an established modality in the management of carotid-cavernous sinus fistula [Fig. 4].7
This study reveals an association of spontaneous CCF with hypertension in three female patients. It is probable that advancing age, menopause, hypertension and childbirth may affect some preexisting subclinical lesions in the arteriolar system like aneurysms, leading to the development of spontaneous CCF.
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