Teaching Case

A 62-year-old woman self-refers to the emergency department with 4-day history of right frontal headache, right-sided tinnitus and a right-sided oculomotorius nerve-paresis with loss of depth perception and strabismus. One month prior, she suffered minor craniocerebral trauma with a parietal left-sided superficial wound requiring no significant intervention.

A contrast-enhanced computed tomography (CECT) showed a tangled bundle of tortuous vessels centered around a bulging right cavernous sinus (CS) with attenuation similar to the internal carotid artery (ICA). There was an engorgement and early enhancement of the superior and inferior ophthalmic vein (SOV and IOV). Furthermore, there was engorgement and early enhancement of the inferior petrosal sinus and the suboccipital plexus which then drained to the right deep cervical vein.

Subsequent diagnostic conventional angiography confirmed a direct high-flow connection between the ICA and the cavernous sinus with flow reversal in the SOV and intracerebral veins. After contrast injection in the proximal ICA, there was almost no filling of the distal ICA.

Based on these findings, a diagnosis of caroticocavernous fistula was made.

Caroticocavernous fistulas (CCF) are rare and often post-traumaticaly acquired communications between the carotid circulation and the cavernous sinus. CCFs can be anatomically classified according to the Barrow classification. The fistula discussed in this case is a direct shunt between the ICA and the CS (Barrow type A), which is by far the most common type, accounting for approximately 75-80% of all CCFs. 95% of these type-A CCFs are post-traumatic [1]. Dural or indirect fistulisations are further divided into shunts originating from meningeal branches originating from the ICA (type B), the external carotid artery (ECA) (type C) or from both the ICA and ECA (type D) [2].
This case demonstrates some of the clinical and radiological hallmarks of caroticocavernous fistulas. Clinically one can distinguish pulsatile tinnitus and deficits in the 3rd cranial nerve. Other signs are deficits in cranial nerves IV-VI, visual impairments, glaucoma and even pulsatile exophthalmos. In CT/MR imaging, one can distinguish an enlarged and early enhancing cavernous sinus and ophthalmic veins. Other signs are orbital fat oedema, enlargement of the extraocular muscles, arterialization of other cranial veins, and skull base fractures of the sphenoid or the carotid canal in the temporal bone and subarachnoid haemorrhage (SAH) from associated trauma [3, 4].
Interesting but not surprising is the relationship between the venous drainage pattern and the clinical presentation. Anterior drainage through the orbital veins induces orbital congestive symptoms. Posterior and inferior drainage induces cranial nerve compression or congestive changes in the posterior fossa and brainstem [5]. Also, these distinct drainage patterns and the often-absent drainage to the contralateral CF, instead of an evenly distributed drainage to all draining veins, indicate that the cavernous sinus is in fact not a cavernous or largely open space at all, but a vastly compartmentalized structure, which directs drainage from the CCF towards one of many pathways [3].
Treatment of CCFs largely varies and is mainly dependent on the clinical presentation. Low-flow CCFs, usually types B/C/D, are managed conservatively. High-flow CCFs, usually type A, require endovascular or surgical treatment [6]. The therapy of choice is embolization of the CCF. For obvious reasons, preservation of the ICA is preferred with only a selective occlusion of the cavernous sinus as the main objective. However, the longer the time of presentation after injury the larger the fistula and the larger the fistula the larger the chance the ICA needs to be sacrificed to successfully close the CCF [4].
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