Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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September 23, 2021
Traumatic Carotid Cavernous Fistula (Barrow Type A)
- Background:
- CCFs are divided according to communication and hemodynamics in the Barrow classification: type A (direct, high flow) and type B-C-D (indirect, low flow).
- This case represents a direct high-flow CCF (Barrow type A). Different causes are known, including traumatic (skull fracture, penetrating injury, iatrogenic) and spontaneous (ruptured carotid aneurysm, connective tissue disease).
- The presence of fibromuscular dysplasia in both cervical ICAs probably predisposed this patient to wall rupture with lower energy trauma. This can be attributed to shear forces between the fixed ICA attachments at the lacerum and anterior clinoid due to rotational injury rather than direct injury by skull base fracture or penetrating injury.
- Clinical Presentation:
- Clinical features are variable and most patients present with orbital symptoms.
- Classical Dandy triad in Barrow type A CCFs shows pulsatile exophthalmos (90%), chemosis (90%), and ocular bruit.
- Key Diagnostic Features:
- CT/MRI with contrast and CTA/MRA show indirect signs of CCFs like enlargement and lateral convexity of the ipsilateral CS, bilateral CS enlargement, dilated or asymmetric SOV, abnormal flow voids in the CS, extraocular muscle enlargement, proptosis, and orbital edema.
- Cerebral angiography is the gold standard and shows early opacification of venous structures.
- Differential Diagnoses:
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Vascular causes
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Indirect CCF: Network of tiny meningeal arterial vessels in wall of cavernous sinus
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Ophthalmic vein thrombosis or compression: Orbital venous congestion
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Cavernous sinus thrombosis: Filling defect in venographic sequences and loss of flow void in spin-echo sequences
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Soft-tissue lesions of the orbit
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Tumors: Orbital mass lesion of variable location, signal, and enhancement; usually painless indolent course
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Extraocular muscle enlargement (thyroid-associated orbitopathy, orbital pseudotumor, sarcoidosis, IgG4-related disease, lymphoma): Diffuse enhancement and enlargement of extraocular muscles with variable DWI/T2 signal; anterior tendon spared, orbital fat infiltration and “I’M SLOw” mnemonic for thyroid orbitopathy; low T2 signal, lacrimal gland enlargement, and pachymeningitis in IgG4-related disease; DWI restriction in lymphoma; orbital pain in orbital pseudotumor
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Treatment:
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Conservative (manual compression and medical therapy); suitable for indirect CCFs, as they may regress spontaneously in 10–60% of cases
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Endovascular in symptomatic direct CCFs and indirect CCFs with progressive symptoms
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Surgery/radiosurgery used in failed endovascular therapy cases
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