Detection and classification of cranial dural arteriovenous fistulas using 4D-CT angiography: initial experience

Abstract

Background and purpose: The criterion standard to diagnose and classify cranial DAVFs is DSA. Since this is invasive, relatively expensive and time-consuming, a noninvasive alternative is of interest. We aimed to evaluate the capabilities and pitfalls of 4D-CTA in a consecutive series of patients who presented with a newly diagnosed cranial DAVF, as demonstrated by conventional DSA.

Materials and methods: Eleven patients were included in this study after biplane DSA demonstrated a cranial DAVF. They subsequently underwent 4D-CTA imaging by using a 320-detector CT scanner. DSA and 4D-CTA studies were independently read by 2 blinded observers, by using a standardized scoring sheet. 4D-CTA results were analyzed with DSA as the criterion standard.

Results: In 10 cases, there was full agreement between DSA and 4D-CTA regarding the Borden classification. However, in the remaining patient, a slow-filling DAVF with a low shunt volume was missed by both readers on 4D-CTA. In all 10 detected cases, ≥ 1 of the major contributing arteries could be identified with 4D-CTA. Although, by using DSA, the 2 observers identified additional arterial feeders in 7 and 8 cases, respectively, these discrepancies did not influence clinical decision making.

Conclusions: Although novel 4D-CTA imaging may not rule out a small slow-flow DAVF, it appears to be a valuable new adjunct in the noninvasive diagnostic work-up, treatment planning, and follow-up of patients with cranial DAVFs.

Fig 1.

Imaging of a 65-year-old man who presented with an intracranial hemorrhage and whose DAVF was missed by 4D-CTA. A, Nonenhanced cranial CT scan on admission demonstrates the presenting hemorrhage. B, DSA, lateral view after left ECA injection, demonstrates abnormal retrograde filling of a pial vein (arrow), indicative of a DAVF. C, Lateral view of 4D-CTA, maximum intensity projection of the early venous phase, shows the same pial vein (arrow). Because visualization of the pial veins is expected on global opacification, only early filling would indicate a DAVF. However, due to the slow flow through the fistula, early venous filling could not be identified. Hence, this 4D-CTA study was read as having normal findings.

Fig 2.

Imaging of a 60-year-old woman who presented with a right-sided pulse-synchronous tinnitus. A, DSA, lateral view after right ECA injection, demonstrates a DAVF (Borden I and Cognard I) at the level of the left sigmoid sinus (large arrow). The lesion is fed through a small arterial network (small arrow), which is mainly supplied by a branch from the occipital artery (large arrowhead) and to a lesser degree by a branch from the middle meningeal artery (small arrowhead). B, Lateral view of 4D-CTA, maximum intensity projection of late arterial phase, shows the early venous drainage into the right sigmoid sinus (large arrow). Compared with the DSA, the 4D-CTA is in agreement with regard to the site and classification of the lesion, as well as to its dominant feeder from the occipital artery (large arrowhead). However, although the smaller feeder from the middle meningeal artery can be seen (small arrowhead), neither reader had recorded it as such The small arrow indicates the arterial network feeding the fistula.

Fig 3.

Imaging of a 47-year-old man who presented with a pulse-synchronous occipital bruit. A, DSA, lateral view after selective injection of the left occipital artery, demonstrates an extensive fistula at the torcular and left transverse sinus with cortical venous reflux (arrows). B, The later phase of the same injection demonstrates additional retrograde sinusoidal flow into the superior sagittal sinus (arrow). It was scored as Cognard grade IIa+b, due to both sinusoidal and pial reflux. C, Lateral view of 4D-CTA, maximum intensity projection of late arterial phase, shows early venous filling with cortical venous reflux (arrows). D, The venous phase of the same 4D-CTA study shows filling of the superior sagittal sinus, which is presumed to be antegrade. Because vascular opacification is nonselective, the temporal resolution is insufficient to recognize retrograde superior sagittal sinus filling. Thus, on the basis of this study, the lesion was erroneously scored as Cognard grade IIb.