Assessment of dural arteriovenous fistulas of the cavernous sinuses on 3D dynamic MR angiography

BACKGROUND AND PURPOSE: Flow voids within the cavernous sinuses and/or certain venous drainage on spin-echo MR imaging and time-of-flight (TOF) flow enhancement on MR angiography (MRA) have indicated high-velocity shunt flow and have been used for screening patients with dural arteriovenous fistulas (DAVFs) of the cavernous sinuses. In this investigation, the capabilities of 3D dynamic MRA as a flow-independent approach and those of conventional MR imaging techniques were compared with selective angiography for the diagnosis of DAVFs of the cavernous sinuses.MATERIALS AND METHODS: This retrospective study involved 18 patients with angiographically proved DAVFs of the cavernous sinuses and 12 control subjects. Sixteen partially overlapping sequential MR images were acquired on contrast-enhanced 3D dynamic MRA between the petrosal bone and the orbital roof. Two experienced observers blinded to the clinical data and results of angiography independently graded 3D dynamic MRA, fast spin-echo T2-weighted imaging (FSE T2WI), and TOF MRA.RESULTS: The average area under the receiver operating characteristic curve values and interobserver κ scores for the diagnosis of DAVFs on 3D dynamic MRA, FSE T2WI, and TOF MRA were 0.99, 0.89, and 0.95; and 0.92, 0.71, and 0.73, respectively. Those for the diagnosis of anterior, posterior, and retrograde cortical venous drainage on 3D dynamic MRA were 0.72, 0.95, and 0.81; and 0.56, 0.50, and 0.49, respectively.CONCLUSION: In this small series, screening 3D dynamic MRA directly demonstrates DAVFs of the cavernous sinuses and has improved diagnostic capability.

In patients with the classic triad of pulsating exophthalmos, orbital bruit, and conjunctival chemosis, the clinical diagnosis of arteriovenous fistulas (AVFs) of the cavernous sinuses is not difficult, and cerebral angiography is performed for definitive diagnosis. However, dural AVFs (DAVFs) without anterior drainage may not cause typical congestive orbito-ocular features, and thrombosis of the draining veins may lead to spontaneous resolution of the disorder.^1–6 Therefore, it is desirable to perform less invasive diagnostic examinations before conventional angiography. So far, flow voids within the cavernous sinuses and/or inferior petrosal sinuses on spin-echo MR images followed by time of flight (TOF) flow enhancement on source images of MR angiography (MRA) have been indicative of AVF.^7–10 Although these are safe and practical methods, dependence on flow velocity sometimes makes it impossible to distinguish fast normal flow from abnormal shunt flow or slow abnormal shunt flow from normal flow.^9–13The recent advancement of MR imaging technology has allowed first-pass contrast-enhanced dynamic MRA and 2D MR digital subtraction angiography to be applied to cerebral arteriovenous malformations (AVMs) or DAVFs.^14–18 In addition, although the conventional use of 3D dynamic MRA for their diagnosis has been difficult due to the limitation of low temporal resolution, its application has been described in recently published articles.^19,20 However, until now, there has not been a comparative study of dynamic MRA and conventional MR imaging for the diagnosis of DAVFs of the cavernous sinuses.According to a study of dynamic CT of the cavernous sinuses²¹ and physiologic studies on the cerebral circulation time,^22,23 it was hypothesized that imaging temporal resolution under several seconds would demonstrate DAVFs of the cavernous sinuses on dynamic MRA. Therefore, we used the 3D data-acquisition technique, a standard pulse sequence, and postulated that early enhancement of the cavernous sinuses was a main direct feature of the shunts. This methodology will improve the diagnostic capability for screening of DAVFs of the cavernous sinuses.