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2013 Neurocritical Care Society Practice Update

CAVERNOUS CAROTID AND

DURAL ARTERIOVENOUS FISTULAS

Owen Samuels, MD

Emory University

Atlanta, GA

Adam Webb, MD

Emory University

Atlanta, GA

OVERVIEW AND EPIDEMIOLOGY

Arteriovenous fistulas are abnormal shunts between the arterial and venous circulation. Dural

arteriovenous fistulas (DAVFs) and cavernous carotid fistulas (CCFs) are forms of arteriovenousfistulas in the central nervous system. The incidence in the population is unknown but they are

thought to make up 5-20% of intracranial vascular malformations [1].

DAVFs are direct connections between meningeal arteries and draining veins contained within

the dura. They can be spinal or intracranial. Though the majority of DAVFs are thought to be

acquired lesions, most are idiopathic, while some result from cranial surgery, trauma, or venous

sinus thrombosis. Venous outflow obstruction can precede formation of DAVFs [2].

DAVFs are classified predominantly by their venous drainage. The Borden classification system

divides DAVFs into 3 types depending on if they drain into dural venous sinuses or into

subarachnoid veins (See Table 1) [3].

CCFs are divided into direct and indirect forms. Direct CCFs are high flow shunts usually

resulting from trauma or aneurysm rupture causing direct communication between the

cavernous portion of the internal carotid artery and the cavernous sinus. Indirect CCFs are more

akin to DAVFs with indirect communication between the carotid circulation (either internal or

external or both) and the cavernous sinus through dural arteries and veins. The cause of

indirect CCFs is unclear and likely shares a similar pathophysiological mechanism with DAVFs.

CCFs are classified as Type A-D depending on the flow rate and arterial supply (See Table 2) [4].

Spontaneous CCFs are more common in middle-aged and elderly women. Other risk factorsinclude pregnancy, systemic hypertension, connective tissue diseases and trauma [5].

PATHOPHYSIOLOGY

Patients with DAVFs may present with hemorrhage or neurological symptoms secondary to

venous congestion. Hemorrhages may be intracerebral, subarachnoid or subdural. A recent


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study described 50% of ruptured DAVFs presenting with pure intracerebral hemorrhage and

50% presenting with a combination of intracerebral and subarachnoid or subdural hemorrhage

[6]. Neurological symptoms are related to the anatomical location of the fistula and venous

drainage.

Borden type II and III DAVFs are more likely to present with clinical symptoms and orhemorrhage. The risk of hemorrhage is about 2% per year [7].

Factors associated with an increased risk of hemorrhage include cortical drainage, retrograde

venous drainage, venous varix, and drainage into the vein of Galen [8].

CCFs allow high-pressure arterial blood flow to be transmitted to the cavernous sinus creating

venous hypertension. This predominantly affects the ophthalmic venous system.

CLINICAL FEATURES

Symptoms and Exam Findings

DAVFs with venous drainage into the transverse or sigmoid sinus may present with pulsatile

tinnitus. Those involving the cavernous sinus may present with ophthalmoplegia, chemosis,

proptosis, and retroorbital or facial pain. Patients may present with seizures, impairment of

consciousness or cognition as well as with symptoms of intracranial hypertension. Patients with

spinal DAVFs may present with myelopathy. Symptoms may be acute, especially with

hemorrhage, or may present in a subacute progressive or even remitting/relapsing manner.

CCFs present with a combination of a cavernous sinus and orbital syndrome with variable

ophthalmoplegia, proptosis, chemosis, and orbital pain. Vision loss may develop with rising

orbital and intraocular pressure. An orbital bruit may be heard. Direct CCFs secondary totrauma or aneurysm rupture demonstrate an abrupt onset of symptoms while indirect CCFs

follow a more indolent course.

DIAGNOSIS

Non-contrast head CT is insufficient to detect a DAVF in the absence of hemorrhage. A high

level of suspicion should be maintained in patients who present with intracranial hemorrhage

without significant risk factors (age, trauma, hypertension, anticoagulation, etc.) and in those

with an atypical pattern of hemorrhage, such as a combination of intracerebral hemorrhage

and subarachnoid or subdural hemorrhage. This should prompt follow up imaging with MRI andMR angiography/venography or catheter angiography.

Additionally, patients who present with subarachnoid hemorrhage in a non-aneurysmal pattern

should raise concern for cerebral or cervical spinal DAVF.

In those patients who present with progressive neurological symptoms without hemorrhage,

subtle venous dilation and or parenchymal signal change may be seen.


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CT findings in CCFs include proptosis, enlargement of the superior ophthalmic vein as well as

prominent extraocular muscles. MRI can demonstrate orbital edema and an abnormal flow void

within the cavernous sinus [9].

Catheter cerebral and/or spinal angiography is the gold standard for diagnosis of DAVFs and isnecessary for any patient with a suspected or confirmed DAVF or CCF for classification and

treatment planning.

TREATMENT

DAVF presenting with hemorrhage or progressive neurological deficits require evaluation for

either surgical or endovascular treatment. Surgical treatment involves the disconnection of

arterialized veins with preservation of the sinus if it is patent or excision of the sinus and

surrounding dura if it is occluded. Endovascular treatment involves transarterial or transvenous

coil or liquid chemical embolization. Stereotactic radiosurgery as a primary or adjunct therapy is

also safe and can be effective.

Recurrence of DAVFs after treatment has been described.

Many CCFs will resolve spontaneously. Direct CCFs and those with intractable symptoms or

those that threaten vision mandate treatment.

The goal of treatment of direct CCFs is the elimination of the communication between the ICA

and the cavernous sinus. This may be accomplished via a transarterial or transvenous route by

embolization of the fistula with a detachable balloon, detachable coils or liquid embolic agent.Additionally, stents may be deployed in the ICA to assist closure. Occasionally, the only

treatment option is sacrifice of the ICA.

The goal of treatment of indirect CCFs is to diminish the shunt between the arterial and venous

circulation and decrease the venous pressure in the cavernous sinus. This can be achieved by

transarterial embolization of the arterial feeders or transvenous embolization of the cavernous

sinus [9].

REFERENCES

1. Wecht D, Awad I. Carotid Cavernous and Other Dural Arteriovenous Fistulas in Primer on

Cerebrovascular Diseases 1997.

2. Brown R, Flemming K, Meyer F, Cloft H, Pollock B, Link M. Natural history, evaluation, and

management of intracranial vascular malformations. Mayo Clinic Proc 2005;80:269-281.

3. Borden JA, Wu JK, Shucart WA. A proposed classification for spinal and cranial dural

arteriovenous fistulous malformations and implications for treatment. J Neurosurg

1995;82:166-179.


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4. Barrow DL, Spector RH, Braun IF, Landman JA, Tindall SC, Tindall GT. Classification and

treatment of spontaneous carotid-cavernous sinus fistulas. J Neurosurg 1985;62:248-256.

5. Miller N. Diagnosis and management of dural carotid-cavernous sinus fistulas. Neurosurg

focus 2007;23:E13.

6. Cordonnier C, Al-Shahi Salman R, Bhattacharya JJ, Counsell CE, Papanastassiou V, Ritchie V,

Roberts RC, Sellar RJ, Warlow C. Differences between intracranial vascular malformationtypes in the characteristics of their presenting haemorrhages: prospective, population-

based study. J Neurol Neurosurg Psychiatr 2008;79:47-51.

7. Brown R, Wiebers D, Nichols D. Intracranial dural arteriovenous malformations: a clinical,

radiologic, and long-term followup study [abstract]. Stroke 1992;23:157. Abstract 85.

8. Awad I, Little J, Akrawi W, Ahl J. Intracranial dural arteriovenous malformations: factors

predisposing to an aggressive neurological course. J Neurosurg 1990;72:839-850.

9. Gemmete JJ, Ansari SA, Gandhi DM. Endovascular techniques for treatment of carotid-

cavernous fistula. J Neuro-Ophthalmol 2009;29:62-71.

10. Wilson M, Enevoldson P, Menezes B. Intracranial dural arterio-venous fistula. Pract Neurol

2008;8:362-369.


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Table 1. Borden Classification of DAVFs

Venous Drainage Clinical Course

Type I Directly into dural venous sinuses or

meningeal veins

Often benign, high rate of

spontaneous remission

Type II Directly into dural venous sinuses

or meningeal veins but also have

retrograde drainage into subarachnoid

veins

Progressive neurological deficit

or hemorrhage

Type III Directly into subarachnoid veins

without dural sinus or meningeal

venous drainage

Progressive neurological deficit

or hemorrhage

Table 2. Barrow Classification of CCFs

Type A: Direct high-flow shunts between the internal carotid artery and the cavernous

sinus.

Type B: Dural shunts between the meningeal branches of the ICA and the cavernous

sinus.

Type C: Dural shunts between the meningeal branches of the ECA and the cavernous

sinus.

Type D: Dural shunts between the meningeal branches of both the ICA and ECA and the

cavernous sinus.

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