Cerebral dural arterio-venous fistula – Part I: Virtual anatomy and pathoanatomy in CT and MR imaging

Case report of a 60 years old male patient, at first his clinical symptoms were interpreted as a cerebrovascular stroke. Acute imaging work up with CT, MRI and catheter angiography of the cerebral arteries and veins revealed final diagnosis of an occipital dural arteriovenous fistula classified Cognard Typ IV.


Introduction
Dural arteriovenous fistula (DAVF) is a type of AVM in which there is a communication between dural arteries and cerebral venous sinuses. These lesions constitute 10-15% of all cerebral AVMs and most of them seemed to be acquired, only some are congenital. There is a female to male ratio of 2:1 and most of them are diagnosed in the fifth and sixth decade. The distinguishing feature between DAVF and cerebral AVM is the fact that there is no parenchymal nidus and there is a dural arterial supply [1].
In this report we demonstrate the case of a 60-year old man, who came to our hospital with clinical suspicion of cerebrovascular stroke. Initial imaging work up included CT and MR scans, furthermore digital subtraction angiography of the cerebrovascular arteries/veins was carried out additionally.

Case report
We present the case of a 60-year old male patient, who was transferred to the emergency room with violent headache, dysesthesia of the right upper and lower limb and unconsciousness for an hour one day before with retrograde amnesia now. The neurologists suspected an ischemic stroke.
The patient´s history was largely unremarkable, mild arterial hypertonus was well treated with an ACE-Inhibitor. The patient denied any previous neurological diseases.
At first, a non contrast enhanced CT scan of the brain was performed to exclude cranial hemorrhage. This showed pronounced, slightly hyperdense tubular structures (Figure 1a

Discussion
Dural arterio-venous fistulas are arteriovenous shunts, supplied by a dural artery to a dural venous channel, mostly located near a major venous sinus. These fistulas are divided into 5 grades ( Table 1).
Most of them seem to be acquired (i.e. trauma, surgical, chronic infection or sinus thrombosis), some of them are congenital. In the pediatric population, most of them are associated with venous anomalies.
Dural arterio-venous fistulas are diagnosed in all age groups, mainly in the fifth and sixth decades of life. There is a higher incidence in female patients (female to male ratio 2:1), estimated incidence is 0,17 cases in a population of 100.000. They represent 10-15 % of cerebral vascular malformations [2].
The dilated veins in the left hemisphere were best seen in the contrast-enhanced T1-weighted 3D gradient-echo sequence ( Figure 5).
Based on these MR findings, we suspected a vascular malformation, most likely in the sense of a dural arterio-venous fistula. Therefore, the next step was to perform an intra-arterial digital subtraction angiography to confirm this suspicion.
The intra-arterial digital subtraction angiography then verified an arterio-venous fistula with feeders from the occipital artery and a petrous branch of the middle meningeal artery. There was an arterial inflow into the superficial temporal vein with retrograde filling into cortical veins and a clearly dilated draining vein ( Figure 6). Therefore, Figure 5. The contrast-enhanced T1-weighted 3D gradient-echo sequence best shows the multiple congested and tortuous veins in the left hemisphere  Copyright: ©2020 Hofko M. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.