1. (dural arteriovenous fistula)
THE NEW AGE OF DAVF
(dural arteriovenous fistula)
D Preciado, MD; J Perendreu, MD; J Branera, MD; B Consola, MD; V P Beltran Salazar, MD; D Canovas, MD.
Department of Radiology, Section of Vascular and Interventional Radiology
UDIAT.CD. SDI. Corporació Sanitaria Parc Tauli. Sabadell, Barcelona (Spain)

2. Treatment: indications and new techniques
The new age of DAVF
Basics of DAVF
Etiopathology
Natural history
Clinical & Diagnosis
Classification
Imaging findings
Treatment: indications and new techniques

3. Usually acquired lesions, may occur secondary to
Basics of DAVF
Dural arteriovenous fistulas (DAVFs) are pathologic shunts between dural arteries and dural venous sinuses, meningeal veins, or cortical veins; they consist of abnormal arteriovenous communications developed within a venous space contained between the two layers of the dura mater.
DAVFs are rare, representing 10% to 15% of intracranial vascular malformations.
Usually acquired lesions, may occur secondary to
dural sinus thrombosis
venous hypertension
trauma

4. Basics of DAVF DAVFs most often involve the following sinuses:
1. Transverse
2. Cavernous
3. Sigmoid
Tentorial DAVF are the most aggressive. Other clincally aggressive DAVFs are usually associated with leptomeningeal venous drainage or reflux.
The gold standards for DAVFs are
angiography for diagnosis
endovascular intervention for treatment
Goal: Total fistula occlusion without interfering with normal dural venous drainage
Method: By transarterial and/or transvenous routes or direct puncture of affected dural sinus
DAVFs could remain clinically silent or involute spontaneously.

5. Venous sinus thrombosis Intracranial hemorrhage
Etiopathology
Venous sinus thrombosis
Predisposing factor: hypercoagulability
Venous hypertension
Opens up the microvascular connections within the dura; these channels become hypertrophied, resulting in direct shunting between the arteries and veins. If the DAVF grows pial supply could be recruited from parenchymal vessels.
Cortical venous
reflux
The involved dural sinus receives arterialized blood flow that can lead to mechanical obstruction of the sinus and result in retrograde drainage of the cortical veins.
Intracranial hemorrhage
The cortical veins may dilate, predisposing to intracranial hemorrhage.

6. Natural history
Venous drainage, in particular reflux into pial veins correlates with DAVF pattern.
DAVFs that present with intracranial hemorrhage or nonhemorrhagic neurologic deficits have a higher risk of new significant events than asymptomatic fistulas.
Cortical venous drainage and aggressive symptomatology are clearly linked to unfavorable natural history.

7. Natural history DAVFs could have a dynamic course.
DAVFs progress to higher grade lesions, in 3 clinical situations:
- spontaneously.
- after an uneventful diagnostic cerebral angiogram.
- after partial treatment.
Factors predisposing to an aggressive course include:
- leptomeningeal (cortical) venous drainage and galenic drainage (deep veins).
- variceal or aneurysmal venous dilatations.
- location in the tentorium.
Any change in patient’s symptoms can reflect a variation of the venous drainage pattern and requires further diagnostic examinations.

8. CLINICAL MANIFESTATIONS
Clinical & Diagnosis
CLINICAL MANIFESTATIONS
(Signs/symptoms depend on site, type of the shunt)
Benign course
Malignant presentation
(sex, lesion location, and venous drainage pattern , particularly cortical venous reflux (CVR))
Incidentally discovered
Asymptomatic lesions
Non-hemorrhagic neurological dysfunction
Intracranial hemorrhage
Death

9. Clinical & Diagnosis CT:
Often the first imaging test to rule out intracranial bleeding after focal neurologic signs.
Findings are often normal; sometimes an area of low density due to edema of chronic venous congestion.
Clinical & Diagnosis
CT angiography:
Can show details of angioarchitecture.
Can be normal if shunts are small.
In aggressive DAVF, we can see enlarged cortical draining veins with tortuous dural feeders and enlarged dural sinus.
Angiogram shows a superior longitudinal DAVF (Cognard IV) involving branches of both external carotid arteries and retrograde venous drainage through superficial cortical veins.
Simple cranial CT shows an acute hematoma in the frontopareital parenchyma.

10. Clinical & Diagnosis MRI can show:
Thrombosed or stenosed dural venous sinus; dilated cortical veins without a parenchymal nidus; thickened dural leaflet; hypertrophied pachymeningeal arteries; dilated, tortuous, and variceal venous channels.
Focal T2 hyperintensity in adjacent brain due to retrograde leptomeningeal venous drainage (RLVD) and venous perfusion abnormalities.
MRI: Focal hyperintensity in T2 due to RLVD.
Angiogram: DAVF in the straight sinus—vein of Galen.
MRA shows dilated cortical veins without a parenchymal nidus

11. Clinical & Diagnosis Angiography:
Gold standard for diagnosis and planning therapy.
Identify feeders, type of venous drainage, retrograde flow, occlusion of sinuses, and circulation time.
Common findings:
- Multiple arterial feeders (dural branches, most commonly from ECA followed by from lCA).
- Involved dural sinus often thrombosed.
- Cortical venous reflux.
- Venous ectasia and cortical venous collaterals.
- Variceal or aneurysmal venous dilatations.

12. Right external carotid
Imaging findings
Right external carotid
Left external carotid
Right branch of the ophthalmic artery
Angiography shows parasagittal DAVF nourished by various subsidiary arteries of both external carotids and the right branch of the ophthalmic artery .

13. Imaging findings
Left transverse sinus DAVF with multifocal arteriovenous shunts, and dural sinus disease with network of tiny "crack-like“ vessels in the wall.
Longitudinal sinus
Left transverse sinus DAFV
Occipital artery
Cerebral angiogram (sagital view) Cognard Type IIA: Located in main sinus, reflux into sinus but not cortical veins.

14. Clinical & Diagnosis Differential diagnosis: - Mixed pial-dural AVM:
• True pial supply to DAVF is rare.
• Usually occurs with large posterior fossa or superficial hemispheric AVM.
- Thrombosed dural sinus:
• Collateral/congested venous drainage can mimic DAVF.
• Can be spontaneous, traumatic, infectious (thrombophlebitis).
- Vascular neoplasm:
• Acutely thrombosed DAVF may enhance, have edema/mass effect, mimic a neoplasm.
• Neoplasms usually do not invade dura, but cause sinus thrombosis.

15. Cognard classification is based on:
The most widely used classification are Cognard and Borden.
Classification is based on the correlation between the angiographic characteristics of the DAVFs and their clinical presentation.
Cognard classification is based on:
- direction of dural sinus drainage.
- the presence or absence of CVR (cortical venous reflux).
- the venous outflow architecture (nonectatic cortical veins, ectatic cortical veins, or spinal perimedullary veins).
Cognard classification enables accurate comparison of clinical and radiological parameters:
- Lack of CVR (Cognard types I and IIa) is associated with a benign natural history with a low risk of intracranial hemorrhage.
- Presence of CVR (Cognard type IIb-V) is an aggressive feature and is associated with a high risk of hemorrhage.

16. COGNARD CLASSIFICATION OF DAVF
TYPE I
Anterograde drainage into sinus.
TYPE II
IIA
Drainage into main sinus with reflux into secondary sinus.
IIB
Drainage into main sinus with reflux into cortical veins.
IIA + IIB
Drainage into main sinus with reflux into secondary sinus(es) and cortical veins.
TYPE III
Direct cortical venous drainage without ectasia
TYPE IV
Direct cortical drainage with venous ectasia
TYPE V
Drainage into the spinal perimedullary veins.

17. Imaging findings
DAVF at sigmoid sinus: Cognard type I. Angiography shows arteriovenous fistula at the sigmoid sinus, depending on the dural branches of the external carotid, specifically the occipital, with only anterograde venous drainage into the left sigmoid sinus.
SAGITTAL VIEW
CORONAL VIEW

18. BORDEN CLASSIFICATION OF DAVF
Borden classification is based on:
- the site of venous drainage.
- the presence of cortical venous reflux (CVR).
- number of fistulas (single-hole or multiple-hole fistulas).
Simplicity without loss of predictability.
Borden type I DAVFs have a benign clinical course and a high rate of spontaneous remission.
BORDEN CLASSIFICATION OF DAVF
TYPE I
Venous drainage directly into dural venous sinus or meningeal vein.
TYPE II
Venous drainage into dural venous sinus with cortical venous reflux
TYPE III
Venous drainage directly into cortical veins.

19. o Endovascular embolization.
Treatment
o Conservative treatment: In DAVFs with benign course: symptomatic treatment and supportive measures.
o Endovascular embolization.
o Surgical resection: Indicated only in cases where endovascular approaches have failed or are not feasible.
o Stereotaxic radiosurgery: Reserved for carefully selected DAVFs for which endovascular and surgical options have been exhausted.
The risk of hemorrhage remains during the latency period until the vessel thromboses and the fistula closes, so it is inappropriate as the primary treatment in hemorrhagic DAVFs due to the high risk of rebleeding.

20. Endovascular Treatment
o Endovascular embolization using transarterial or transvenous approaches has become a first-line treatment for DAVFs, especially since the advent of ONYX ® (eV3; Neu-
rovascular Inc., Irvine, CA, USA).
o The goal is complete and definitive angiographic fistula obliteration.
o To obtain complete obliteration of the fistula or satisfactory flow reduction with suppression of CVR, some lesions need multiple microcatheter embolization or multiple treatment sessions.
o Transvenous embolization with detachable coils and/or in combination with ONYX ® is possible when transarterial embolization is unavailable.
o The balloon-assisted flow control technique is an effective method for high-flow DAVFs.
o Angiographic follow-up 3 to 9 months after treatment.
ENDOVASCULAR TREATMENT PROCEDURE

21. Endovascular Treatment
PROCEDURE DETAILS I:
1- Patients need general anesthesia and anticoagulation during the treatment.
2- Transarterial approach (via femoral artery) using a 6F guiding catheter.
3- Cerebral angiogram required to confirm the diagnosis, determine angiographic characteristics, and assist treatment planning.
4- Using a roadmapping technique, a microcatheter (in our center Marathon microcatheter (EV3, Irvine, CA)) is coaxially navigated through the guiding catheter into a selected feeding artery.
5- A microguidewire helps advance the microcatheter until it reaches or comes as close as possible to the fistula.

22. Endovascular Treatment
ENDOVASCULAR TREATMENT PROCEDURE
PROCEDURE DETAILS II:
6- Superselective angiography: to reveal the focal angioarchitecture and dynamic flow characteristics of the fistula.
7- Endovascular material (EVOH (Ethilene Vinyl Alcohol (ONYX ®)) / Nbutyl-2- cyanoacrylate, NBCA) and concentration of the embolized material to use is based on the distance from the fistula, flow velocity of the shunt, and risk of venous migration. Sometimes coil placement is necessary to decrease the flow velocity at the fistula before injecting the liquid embolic agent.
8- Injection of ONYX ® : it is intermittently injected until the proximal draining veins are completely filled, thereby completely obliterating the fistula.

23. Treament with EVOH (Ethilene Vinyl Alcohol (ONYX ®))
Endovascular Treatment
DAVF of superior longitudinal sinus
Treament with EVOH (Ethilene Vinyl Alcohol (ONYX ®))
Control shows complete embolization of the DAVF.

24. Imaging findings CORONAL VIEW SAGITTAL VIEW
Angiogram shows DAVF of the left sigmoid-transverse sinus. Anterograde drainage from multiple veins toward the left sigmoid-transverse sinus and retrograde drainage into parietal superficial cortical veins, which are markedly tortuous and collateralized toward the superior longitudinal sinus.
Cerebral angiogram (lateral view): Cognard Type IIB DAVF of the left sigmoid-transverse sinus.

25. Same patient as before, after treatment with ONYX ®
Imaging findings
CORONAL VIEW
Same patient as before, after treatment with ONYX ®
BEFORE
ONYX ®
AFTER
DAVF in the left sigmoid-transverse sinus was embolized with ONYX ® through a 6F guide catheter, together with a microcatheter in the left occipital artery, a branch of the external carotid artery.
About 70% of the DAVF was embolized with ONYX ®; but some cortical reflux remains after treatment

26. Imaging findings
Same patient as before, evolving to Cognard IV ( Direct cortical drainage with venous ectasia)
CORONAL VIEW
SAGITTAL VIEW

27. Imaging findings
COGNARD TYPE III PREONYX ® : Direct cortical venous drainage without ectasia
SAGITTAL VIEW
A direct arteriovenous communication through arteriovenous microconnections at the level of the left anterior parietal cortical vein (near the superior longitudinal sinus), with arterial afferents depending on the right occipital and left medial meningeal , drained by multiple veins through parietal cortical veins that drain the left sigmoid sinus and the superior longitudinal sinus.
CORONAL VIEW

28. COGNARD TYPE III POST ONYX ®
Imaging findings
COGNARD TYPE III POST ONYX ®
Superselective embolization of the left medial meningeal artery with ONYX ® delivered by a microcatheter and a microguide.

29. Cortical reflux has disappeared after treatment with ONYX ®
Imaging findings
COGNARD TYPE III POSTONYX ®
Cortical reflux has disappeared after treatment with ONYX ®
REMEMBER: COGNARD TYPE III PREONYX ® : Direct cortical venous drainage without ectasia
Complete embolization of a DAVF of the left parietal cortical vein with ONYX ®

30. DAVFs are uncommon, and their pathophysiology is complex.
Conclusions
DAVFs are uncommon, and their pathophysiology is complex.
We hope this presentation has made them easier to understand and that you have learned what to account in the general radiologic differential diagnosis.
When the multidisciplinary team decides on treatment, endovascular treatment is the first choice.
Treatment should be tailored to each patient and his or risk factors.
The liquid embolic agent ONYX ® is the safe and efficacious, making it our first choice for these lesions.

31. References
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