Letter: Angioarchitectural Analysis of Arteriovenous Shunts in Dural Arteriovenous Fistulas and Its Clinical Implications

To the Editor: We were intrigued to read the recently published article by Junhyung Kim et al titled “Angioarchitectural Analysis of Arteriovenous Shunts in Dural Arteriovenous Fistulas and Its Clinical Implications.”1 The authors proposed a classification for 4 shunt patterns of dural arteriovenous fistulas (DAVFs) based on the fistula, sinus, and cortical vein connection in the transverse-sigmoid sinus and superior sagittal sinus region: direct sinus fistula, compartmental sinus channel, mural channel, and bridging vein shunt. Different treatment strategies may be performed for various shunt patterns. The authors referred to fistulas that entered the sinus directly from feeding arteries as “direct sinus fistulas.” The “compartmental sinus channels” were identified by arterial feeders converging into a partially thrombosed sinus or a separate sinus channel. Mural channels were outlined as tubular elements that were cut off from the sinus main lumen. Bridge vein shunts were defined as fistulas formed where bridging veins and sinuses meet.1 They also summarized some conclusions, such as the mural channel was directly connected to the cortical vein, which has important therapeutic implications. Following the author's research, readers will gain a better understanding of the angioarchitecture of DAVFs around the sinus region. However, our clinical experience and literature review lead us to believe that the fistulas are not directly at the sinus.2,3 Before the sinus or cortical veins drainage, blood must first travel through the dural veins from the dural arteries and then to the sinuses or bridging veins. A very long or very short segment of the draining dural vein is possible. A dural vein is frequently mistaken for a supplying artery when it is very long. In a number of cases at our center, despite the lack of histopathological examinations, we can identify that the supplying arteries and the draining dural veins are completely different. Arteries branch and taper, and veins receive branches and gradually thicken their lumens. After the selection of feeding arteries and straining veins, the sites at which the calibers between them change from thin to thick are regarded the location of fistulas. The draining dural veins and location of fistulas are also an essential part of angioarchitecture. This understanding of angioarchitecture enables the super-selection of the draining dural veins and the blocking of the drainage veins by transarterial or transvenous embolization to treat DAVF while maintaining the patency of the drainage venous sinus. The authors of this article defined the feeding arteries directly into the sinus or the junction of the bridging veins and sinuses, which, like many other articles, is incorrect. DAVFs in transverse-sigmoid sinus and superior sagittal sinus are sometimes with pial arterial supply.4 Although the authors did not focus on describing feeding arteries, they are an important component of angioarchitecture. When dealing with DAVFs with pial arterial supplies, the treatment strategy will be different. The angioarchitecture of DAVF is so complex and variable that it can be difficult to fully understand without histopathological analyses. We appreciate the authors for introducing novel ideas to the readers.