Applied Radiology

Diagnosis

Dural arteriovenous fistula (Borden type 2)

Findings

Three-dimensional (3D) time-of-flight (TOF) and contrast-enhanced MR images demonstrate dilated left posterior auricular and occipital arteries communicating with distal left transverse sinus (Figures 1 and 2). There is no adjacent FLAIR abnormality (Figure 3). Cerebral angiogram confirms multiple intraosseous feeders from the occipital artery, enlarged superficial temporal and middle meningeal artery branches, and early filling of the adjacent transverse sinus (Figure 4). There is both retrograde flow and anterograde flow within the venous sinuses in the vicinity of the fistula (best appreciated on DICOM images).

Discussion

Dural arteriovenous fistulas (DAVFs) represent abnormal communication of the extracranial or dural arteries with dural venous sinuses, meningeal veins, or cortical veins and comprise approximately 10% to 15% of intracranial arteriovenous malformations.¹ Most cases are idiopathic, but previous dural sinus thrombosis, surgery, and trauma are recognized predisposing conditions.²

Typically, patients will present in the fifth and sixth decades. When lesions involve the transverse or sigmoid sinus, symptomatic patients frequently complain of pulsatile tinnitus. DAVFs involving the cavernous sinus may result in retroorbital pain, proptosis, ophthalmoplegia, or vision loss. Severe presentations, including acute headache, seizure, and focal deficit, are worrisome for intracranial hemorrhage or venous infarct.

Noncontrast computed tomography (CT) is of limited utility but may demonstrate hemorrhage, edema, or subcortical calcification.³ Magnetic resonance (MR) often reveals prominent vessels, edema, white matter changes, hemorrhage, or venous infarction.^1,4 CT angiography and MR angiography are useful for lesion characterization as well as treatment planning, but conventional angiography remains the gold standard.⁵

The Borden classification system characterizes lesions based on drainage pattern and the presence or absence of cortical venous drainage.⁶ Type 1 lesions, or those draining into a dural sinuses with normal antegrade flow, typically follow a benign course. Lesions draining into a dural sinus with some retrograde cortical vein flow (Type 2) or those draining directly into a cortical vein without dural sinus or meningeal venous drainage (Type 3) carry a higher risk venous thrombosis, intracranial hemorrhage, and death.

Embolization either via a transarterial or transvenous approach has become the mainstay of treatment of DAVFs. Surgery is typically reserved for cases of failed or technically infeasible embolization.

1. Kwon BJ, Han MH, Kang HS, Chang KH. MR imaging findings of intracranial dural arteriovenous fistulas: relations with venous drainage patterns. AJNR Am J Neuroradiol. 2005;26:2500-2507.
2. Chung SJ, Kim JS, Kim JC, et al. Intracranial dural arteriovenous fistulas: Analysis of 60 patients. Cerebrovasc Dis. 2002;13:7.
3. Metoki T, Mugikura S, Higano S, et al. Subcortical calcification on CT in dural arteriovenous fistula with cortical venous reflux. AJNR Am J Neuroradiol. 2006;27:1076-1078.
4. Lee SK, Willinsky RA, Montanera W et-al. MR imaging of dural arteriovenous fistulas draining into cerebellar cortical veins. AJNR Am J Neuroradiol. 2003;24:1602-1606.
5. Brown RD Jr., Flemming KD, Meyer FB, et al. Natural history, evaluation, and management of intracranial vascular malformations. Mayo Clin Proc. 2005;80:269-281.
6. 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.