The Borden classification of dural arteriovenous fistulas (DAVF) groups these lesions into three types based upon the site of venous drainage and the presence or absence of cortical venous drainage. It was first proposed in 1995 ¹. At the time of writing (July 2016), it is probably less popular than the more complicated Cognard classification system. 

Structure

The Borden classification divides dural arteriovenous fistulas into three types according to their location and the presence or absence of cortical venous drainage. Unlike the Cognard classification system, it does not assess the direction of flow or the presence of venous ectasia.

Classification

• type I

  • drainage into meningeal veins, spinal epidural veins or into a dural venous sinus

  • normal anterograde flow in both the draining veins and other veins draining into the system

  • equivalent to Cognard type I and IIa, with a favorable natural history ^2,4

• type II

  • drainage into meningeal veins, spinal epidural veins or into a dural venous sinus 

  • retrograde flow into the normal subarachnoid veins

  • equivalent to Cognard type IIb and IIa+b

• type III

  • direct drainage into subarachnoid veins or into an isolated segment of the venous sinus (which results from a thrombosis on either side of the dural sinus segment)

  • equivalent to Cognard type III, IV and V

According to this classification, these lesions are further subclassified in type a (single-hole) or type b (multiple-hole) fistulas.

Prognosis

Clinical course depends on the type as well as location. 

Type I dural arteriovenous fistulas almost invariably have a benign clinical behavior, presenting incidentally or with symptoms of increased dural venous drainage (i.e. pulsatile tinnitus, exophthalmos) provided they are within the intracranial compartment. Aggressive behavior was only found in 2% of such cases ². A significant number of patients will actually demonstrate reduction of the fistula on follow-up ⁷.

Spinal type I dural AVFs can result in myelopathy due to venous hypertension (see spinal DAVF).

Those with cortical venous drainage (type II and III) have a more aggressive natural history, with an increased risk of hemorrhage or of a non-hemorrhagic neurological deficit. Type II was found to have aggressive behavior in 39% and type III in 79% of cases ³. 

In general, the Cognard classification does have a greater ability to separate patients prognostically ².

Zipfel's modification

Zipfel et al ³ have suggested a modification to the Borden classification by integrating data on mode of presentation on estimating the risk of new intracranial hemorrhage or neurological non-hemorrhagic deficits. Since cortical venous drainage is deemed important for risk assessment, the changes regard only Borden types II and III, further subdividing them into symptomatic (2S, 3S), or asymptomatic (including tinnitus or orbital phenomena; 2A, 3A).

Building on the work from Strom ⁴ as well as from Soderman ⁵, the annual event rate for Borden type II or III asymptomatic fistulas has been estimated to be 1.4-1.5% while for symptomatic it appears to be 7.4-7.6% ⁶.