Cranial dural arteriovenous fistulas. Dural AVFs. Important for Neuroradiologists and Neurointerventionalists.

1. Interventional Neuroradiology
Cranial Dural
Arteriovenous Fistulas
Mohamed M.A. Zaitoun, MD
Interventional Radiology Consultant, Zagazig University Hospitals, Egypt
FINR-Switzerland
zaitoun82@gmail.com
Interventional Radiology Unit,
Zagazig University, Egypt

3. Knowing as much as possible
about your enemy precedes
successful battle and learning
about the disease process
precedes successful
management.

4. Cranial Dural Arteriovenous Fistulas
a) Definition
b) Etiology
c) Incidence
d) Pathology
e) Classification
f) Clinical Picture
g) Location
h) Radiographic Features
i) Management

5. a) Definition :
-These lesions comprise arteriovenous
fistulas situated in the meninges and
supplied partly or wholly by dural arteries
-Venous drainage is to dural sinuses and /
or leptomeningeal venous channels

6. b) Etiology :
-The current consensus is they are acquired
lesions , usually developing in response to
thrombosis of a sinus or a lesion that
causes abnormally high venous pressure
-The arguments for a congenital etiology are
weak and based on the observation of
aneurysms , brain AVM and other
arteriovenous fistulas in some patients
-The evidence for their being acquired is
more compelling

7. -DAVFs have been reported in patients with:
1-Histories of previous local trauma
(including surgery , e.g. injection of the
Gasserian ganglion)
2-Hypercoagulability states , such as
pregnancy , use of oral contraceptives ,
middle ear infection
3-A documented previously normal sinus

8. -A history of previous local trauma or
hypercoagulability state was present in 66% of
patients in a recent meta-analysis
-Trauma may rupture arteries adjacent to veins to
create a fistula acutely or result in thrombosis of
a sinus
-It is assumed that transient sinus thrombosis
stimulates production of endothelial growth
factor , which causes angiogenesis , and the
development of arteriovenous shunts in local
dural vessels

9. -At the same time , a change in arteriovenous pressure
gradients opens arteriovenous microshunts between
dural vessels
-This latter process being triggered by raised arterial
pressure , head injury , partition , and sinus compression
by tumor or surgical occlusion of a sinus , though these
are also factors that might precipitate sinus thrombosis
-However , the mechanism of the relationship with sinus
thrombosis is not clear , since sinus thrombosis does not
always cause a DAVF and thrombosis may occur within
them
-Thus , lesions may evolve with changing degrees of
venous thrombosis causing changes in venous drainage
patterns , fluctuations in symptoms and signs , and even
spontaneous closure of fistulas
-Progressive restriction of venous outflow may cause
retrograde cortical venous drainage and venous
hypertension

10. c) Incidence :
-10-15% of all intracranial vascular
malformations
-Age : Lesions have been reported in
children but most present in adult , older
population (50-70 years) compared to
AVM (20-40 years)
-Sex : There is a modest male
predominance , which is most evident for
higher-grade lesions
-Multiple Lesions : Occasionally occur

11. d) Pathology :
-The dura is thickened with intense vascular
proliferation within and around the sinus
wall
-A spongy mass of fibrous tissue is found
inside the sinus , and primary and
secondary arteriovenous shunts are seen
on the venous side of the network
-Stenosis or occlusion of sinuses is frequent
but not always present

12. e) Classification :
1-Cognard Classification :
-Type I : Antegrade drainage into a sinus or
meningeal vein
-Type IIa : As type I but with retrograde flow
-Type IIb : Reflux into cortical veins
-Type IIa + b : Reflux into both sinus and
cortical veins
-Type III : Direct cortical venous drainage
without venous ectasia
-Type IV : Direct cortical venous drainage
with venous ectasia
-Type V : Spinal venous drainage

13. -Symptoms and signs associated with different
drainage patterns :
*Type I : Murmur (bruit) , headache
*Type IIa + b : As above plus intracranial
hypertension , dementia , seizures , cranial
nerve palsy and focal neurological deficits.
Hemorrhage
*Type III & IV : Similar to type II but more often
presents with hemorrhage , venous
hypertension and hydrocephalus

14. 2-Borden Classification :
-Type I : Drainage directly into dural venous
sinuses or meningeal veins
-Type II : Drainage into dural sinuses or
meningeal veins with retrograde drainage
into subarachnoid veins
-Type III : Drainage into subarachnoid veins
without dural sinus or meningeal venous
drainage

15. -These classifications emphasize the importance of
increased pressure in cortical veins to the development
of symptoms or spontaneous hemorrhage
-Aggressive lesions are those with higher grades and
retrograde drainage into cortical or subarachnoid veins ,
they are more likely to cause spontaneous hemorrhage ,
focal neurological deficits and seizures
-Type I lesions , in which drainage is confined to an
adjacent sinus without backflow or reflux , are unlikely to
bleed or cause symptoms other than bruit or headache
-An exception is the type I DAVF of the cavernous sinus in
which drainage is directed anteriorly (i.e. as usual) to
orbital veins but overwhelms their capacity and causes
sight-threatening symptoms , i.e. proptosis ,
ophthalmoplegia and raised intraocular pressure

16. f) Clinical Picture :
-Symptoms & signs secondary to arterialization of
venous system :
1-Bruit
2-Venous hypertension
3-Pulsatile tinnitus (if primary involvement is
sinuses)
4-Hemorrhage
5-Focal neurology
6-Seizures
7-Caroticocavernous fistula may give rise to
proptosis & chemosis

17. -Frequency of DAVFs at different
locations and their usual presenting
symptom :

18. g) Location :
1-Transverse / sigmoid sinus : Most common
2-Cavernous sinus
3-SSS
4-Straight Sinus
5-Other venous sinuses
6-Anterior cranial fossa : Typically only ICA
supply due to meningeal supply of this region
7-Tentorium

19. -At any location , drainage via cortical /
subarachnoid veins may be present at
presentation and this finding is associated
with higher incidences of hemorrhage or
progression of neurological signs
-Patients with DAVFs located in the tentorial
and anterior fossa most commonly present
with hemorrhage

20. h) Radiographic Features :
1-CT & MRI :
-With and without contrast , may show secondary features
of raised intracranial pressure , cerebral edema and
intracranial hemorrhage
-CT may be normal or at best show abnormally enlarged
vessels (e.g. an enlarged superior ophthalmic vein) after
contrast enhancement
-Hypoattenuation of the white matter at CT or hyperintense
T2 signal at MR imaging indicates venous congestion or
infarction which may eventually lead to venous
hemorrhage
-PET or SPECT scans may show increases in regional
cerebral blood volume and decreased cerebral blood
flow in areas affected by raised venous pressure

21. -MRI with contrast is more likely than CT to
demonstrate enlarged cortical veins or venous
lakes in higher grade DAVFs
-MRA / MRV is best performed using a 3D phase
contrast technique with low velocity encoding , in
order to identify the fistula , feeding arteries and
flow reversal in draining veins
-It may be negative if blood flow is slow and its
relatively poor resolution is not able to delineate
the detailed angioarchitecture
-Venogram should identify occlusion or stenosis of
major dural sinuses

22. Borden type 2 dural AVF in a 45-year-old woman who presented with sudden loss of consciousness ,
(a) CT without contrast shows a left temporo-occipital hematoma with intraventricular hemorrhage
, (b) T2 shows multiple flow void vascular structures along the cortical sulci of both occipital
regions , there is white matter edema with T2 hyperintensity in the left occipital lobe with evidence
of a resolving hematoma , no nidus can be identified , (c) Left internal maxillary angiogram reveals
a dural AVF in the left transverse sinus supplied by branches of the left middle meningeal artery ,
note the associated thrombosis of the proximal and distal parts of the transverse sinus creating an
“isolated pouch” and thereby causing reflux from the shunt into the cortical veins

23. 2-Catheter Angiography :
-Still gold standard for diagnosis and
demonstration of morphology on which
classification and treatment planning
based
-Demonstrate early venous filling , the
contribution from external carotid artery
branches (rather than pial vessels) and
shunt location

24. Dural arteriovenous fistula of the transverse sinus , the principal contributing
feeding arteries are the posterior branch of the middle meningeal , the
occipital and the posterior auricular arteries , drainage is to the transverse
and sigmoid sinuses in an antegrade direction without reflux to cortical veins

25. Dural arteriovenous fistula of the cavernous region , an ICA DSA
showing multiple small fistulas arising from branches of the carotid
(i.e. ILT) draining to the superior and inferior ophthalmic veins ,
since blood flows to or from the orbital veins , depending on the
head position and the patient is supine , this a type IIa DAVF

26. Dural arteriovenous fistula of the transverse sinus with its principal
supply from branches of the occipital artery , a type I fistula but the
sigmoid sinus is dilated because of distal stenosis , this may be the
result of the increased blood flow (high flow) stenosis and lead to
retrograde reflux in the transverse sinus or to cortical veins

27. Another dural arteriovenous fistula of the transverse sinus with
antegrade and retrograde flow in the sinus , this is therefore a type
IIa fistula

28. Type III DAVF of the transverse sinus with direct filling a
prominent cortical vein (arrow)

29. A dural arteriovenous fistula of the transverse sinus with filling of part of
the sinus and enlarged cortical veins , this is a type IV DAVF

30. i) Management :
1-Indications for Treatment
2-Aims of Treatment
3-Treatment

31. 1-Indications for Treatment :
-Though treatment should be considered for all
lesions , spontaneous closure has been reported
in ca. 10% of DAVFs of the cavernous region
a) Type I lesions :
-Intervention is only indicated if symptoms are
distressing for the patient
-Although evolution between types (due to opening
or closing of the primary drainage) has been
reported , it is unusual , and if it occurs , it is
usually accompanied by an alteration in
symptoms
-Therefore , if symptoms are stable and tolerated
by the patient , there is no indication for
intervention

32. b) Type II lesions :
-Endovascular treatment is usually
recommended
c) Type III and IV lesions :
-Urgent surgical or endovascular treatment
is indicated

33. 2-Aims of Treatment :
-These are either cure or palliation of symptoms
-For cure , the treatment aim is to completely close
the fistula and the abnormal venous outlet
-Palliative treatments can be difficult to engineer
without risking alterations of the venous
drainage pattern and so are usually performed
transarterially
-The treatment approaches recommended are
based on the observed differences in natural
history for DAVFs

34. -DAVFs at different locations , relationship of
location to presentation and management :
1-Anterior Cranial Fossa
2-Cavernous Sinus
3-Sigmoid / Transverse Sinuses
4-Superior Sagittal Sinus
5-Tentorial Incisura
6-Basal Tentorial
7-Torcular
8-Foramen Magnum

35. 1-Anterior Cranial Fossa :
-Feeders : Anterior and posterior ethmoidal
arteries or anterior falcine artery
-Drainage : Frontal cortical , basal veins &
sphenoparietal sinus
-S&S : Up to 90% chance of hemorrhage
-Treatment : Usually surgical

36. 2-Cavernous Sinus :
-Feeders : Branches of ILT and MHT (ICA) ,
recurrent meningeal artery (OphA) , capsular
artery (ICA) , MMA , accessory meningeal
artery, artery of foramen rotundum (ECA) &
contralateral supply
-Drainage : Ophthalmic veins , inferior / superior
petrosal sinuses , sphenoparietal sinus and
frontal cortical veins
-S&S : Headache , bruit , ocular symptoms
(chemosis , proptosis , visual disturbance ,
raised intraocular pressure & ophthalmoplegia)
-Treatment : Conservative (spontaneous closure
recognized) compression therapy or
endovascular (transvenous or transarterial) , the
venous approach is usually the treatment of
choice

37. 3-Sigmoid / Transverse Sinuses :
-Feeders : Jugular artery (APA) ,
transmastoid branch (OA) , MMA,
meningeal branches of VA and marginal
tentorial artery (ICA)
-Drainage : Sigmoid sinus , transverse sinus
, IJV
-S&S : Headache , pulsatile tinnitus and
bruit , neurological deficits : focal deficits ,
memory changes , visual disturbance
-Treatment : Compression therapy ,
endovascular (transarterial or
transvenous) , combined endovascular
and surgery , or surgery alone

38. 4-Superior Sagittal Sinus :
-Feeders : MMA , STA , OA , also anterior
and posterior falcine arts
-Drainage : Superior sagittal sinus
-S&S : Headache , hemorrhage, bruit
uncommon
-Treatment : Endovascular (transvenous or
transarterial) , combined endovascular and
surgery , surgery alone

39. 5-Tentorial Incisura :
-Feeders : Marginal tentorial artery (ICA) ,
meningeal branches MMA , ICA and VA
-Drainage : Tentorial veins , BVR & lateral
mesencephalic vein
-S&S : High incidence of hemorrhage
-Treatment : Endovascular , combined
surgical / endovascular

40. 6-Basal Tentorial :
-Feeders : Basal tentorial artery (MHT) ,
lateral clival artery (ICA) , meningeal
branches MMA , ICA and VA
-Drainage : Superior petrosal sinus &
petrosal vein
-S&S : Headache , hemorrhage
-Treatment : Endovascular or surgery

41. 7-Torcular :
-Feeders : Meningeal branches of OA
(bilateral) & VA
-Drainage : Medial occipital , infratemporal
and cerebellar veins
-S&S : Bruit uncommon , headache and
hemorrhage
-Treatment : Endovascular or surgery

42. 8-Foramen Magnum :
-Feeders : Hypoglossal artery (APA) ,
anterior meningeal artery (VA) ,
transmastoid artery (OA) & medial clival
artery (ICA)
-Drainage : Subarachnoid , vertebral veins
-S&S : Bruit , myelopathy & hemorrhage
-Treatment : Endovascular (transarterial or
transvenous) & surgery

43. 3-Treatment :
-The decision to treat is based on clinical
presentation , location , anticipated natural
history and venous drainage
-The treatment options are :
a) Conservative Management
b) Surgery
c) Stereotactic Radiotherapy
d) Embolization

44. a) Conservative Management :
-Observation without intervention is suitable for a
type I fistula if symptoms are tolerated , since
spontaneous regression of DAVFs can occur
-The decision to pursue this management should
be re-evaluated if symptoms change
-Arterial compression may be useful in
asymptomatic type I and type IIa DAVF
-It involves the patient compressing the cervical
carotid or occipital artery using their contralateral
hand

45. -The procedure should start with short periods of
compression , repeated several times a day and
the frequency and duration of compression
increased over 3-4 weeks
-Compression is performed sitting or lying and has
been shown to be effective in inducing
thrombosis of the DAVF in 20-30% of patients
-It is contraindicated in patients with
atherosclerosis

46. b) Surgery :
-Surgical ligation of feeders is inappropriate
therapy
-Skeletisation of the dura around a DAVF involves
excision of the nidus , sinus and venous
drainage
-It may be accompanied by significant blood loss
and is reserved for lesions with direct
leptomeningeal drainage
-It is considered the treatment of choice for
anterior cranial fossa lesions , but combined
endovascular treatments are also useful

47. c) Stereotactic Radiotherapy :
-Reports of treatment with stereotactic
radiosurgery claim complete occlusion
rates of 44-87% without serious
complications
-Its major disadvantage is the delay in
response and so it is generally used for
low-risk lesions or lesions otherwise
untreatable
-Its use in combination with transarterial
embolisation has been reported as
effective after incomplete treatments

48. d) Embolization :
-Prior to any endovascular treatment ,
comprehensive catheter angiography must be
performed
-This should include six-vessel cranial angiography
with careful assessment for arterial variants and
EC-IC anastomosis
-Contralateral anastomoses and collaterals are
commonly found
-The choice of transvenous or transarterial
approach depends on the location , venous
drainage type and the available endovascular
access

49. -Thus , lesions with multiple arterial pedicles
draining to a redundant sinus have
traditionally been treated by endovascular
occlusion of the sinus (under angiographic
control)
-Access depends on a transvenous route
that can be catheterized , without which
catheterization of the sinus must be
transarterial or percutaneously via a
surgically created window
-Type III and IV DAVFs do not have a simple
connection to the sinus and treatment of
these type of lesions may require a
combination of methods

50. 1-Transarterial Embolisation :
-Is performed with particles or liquid agents
a) Transarterial embolisation with particles
b) Transarterial embolisation with liquid
embolic agents

51. a) Transarterial embolisation with
particles :
-There is a high incidence of recurrence
after arterial embolisation with particles
and so it is rarely performed except prior
to surgery or for palliation of symptoms
-In palliative treatments for Type I and IIa
DAVF , the aim is to reduce the flow
through the fistula , in order to reduce
symptoms , such as bruit

52. *Technique :
-Embolisation is performed using particles in the
150-250 mm range
-It is usually unnecessary (and unwise) to
embolize meningeal feeders arising directly from
ICA or VA
-A free-flow injection which avoids wedging the
microcatheter tip , is best
-Particles are injected until stasis is achieved in the
distal pedicle

53. *Complications :
-If particles >150 mm are used , cranial
nerve palsies are very rare
-Other complications are generic , i.e. those
associated with selective catheterization
and cranial angiography

54. b) Transarterial embolisation with liquid
embolic agents :
-Recently , the transarterial use of n-butyl-2-
cyanoacrylate (NBCA) or Onyx (ev3
Endovascular Inc., Irvine, CA, USA) has
shown great potential and enabled the
treatment of previously incurable DAVFs
-Onyx can be injected from both transarterial
and transvenous routes and extensive
filling of small fistulas achieved from both
antegrade and retrograde approaches

55. -In some instances , using NBCA may be
more appropriate , but generally the
transarterial injection of Onyx allows
multiple small feeding vessels to be
excluded from a single catheter position , it
is easier to control than NBCA and
injections can be stopped before Onyx
enters functional cortical veins

56. *Technique :
-A standard plug-and-push technique is used with
high-density Onyx that helps visualization ,
especially when injecting vessels around the
skull base
-A nondetachable balloon can be placed , to
protect sections of a draining sinus during
embolisation
-In some situations , planning to embed the
microcatheter and leave it in situ allows very
long injections to cure extensive lesions

57. -A detachable-tip microcatheter is a useful device
to use in this situation
-For NBCA , a low-pressure injection under high-
resolution fluoroscopy is performed in order to
avoid opening EC-IC anastomoses using 1:3 or
more dilute mixtures , with Lipiodol
-It is usually impossible to inject as much NBCA as
Onyx and the choice of which to use often
depends on the extent of the intended
embolisation

58. *Complications :
-Delayed hemorrhage
-Cranial nerve palsy

59. 2-Transvenous Embolization :
-The aim of transvenous embolisation is to occlude
the draining system (usually a dural sinus) of the
DAVF so that the low-pressure arterial blood
supply is secondarily occluded
-To prevent complications , it has to be performed
without occluding unique normal venous
drainage pathways from the brain
-It can be performed with fibre coils , controlled
detachment bare or coated coils and liquids
-The disadvantage of coils is that it may take time
for thrombus to completely occlude a sinus , and
they are expensive in time and money

60. *Technique :
-After careful angiographic assessment of the
venous drainage of the brain and the DAVF ,
sections of dural sinus (classically the transverse
sinus) are selected for occlusion
-Access is via the sinus , draining veins or
secondary sinuses , e.g. inferior petrosal sinus
or superior ophthalmic vein to the cavernous
sinus
-Coils are placed in the section to be occluded

61. -The technique is to use controlled detachable
coils first in order to define the boundaries of the
segment to be occluded and then more
thrombogenic fibre coils or liquid agents are
deployed inside the defining boundary coils
-This increases the thrombogenicity of the
embolus
-A technique for temporarily obstructing part of a
sinus with a balloon and then injecting Onyx so
that it refluxes into dural vessels has been
described , but transarterial injection of Onyx is
generally easier

62. *Complications :
-The risks of the transvenous approach are venous
infarction of a territory being drained by a normal
vein and changing the venous drainage of the
DAVF from a benign to a more aggressive
pattern
-Transient worsening of symptoms is reported in
ca. 10% of patients
-The technique is therefore best reserved for
embolisation of veins or sinuses which no longer
contribute to drainage of normal parenchyma
-The additional use of transarterial particles or
liquid embolic to slow venous flow is an option

63. *Postoperative Care :
-It is usually sufficient for patients to recuperate
with bed rest for 24 h with prescribed oral
analgesics
-A short course (48-72 h) of corticosteroids may be
useful to reduce tissue swelling , particularly
when treating lesions causing orbital edema
-A careful postprocedure-documented neurological
examination should be performed

64. *Follow up Imaging :
-DSA or MRA should be performed at 3-6 months
-A preliminary MR scan is helpful in deciding
whether any residual or recurrent symptoms are
related to the DAVF and if this may require
retreatment
-Retreatment can then be planned without the
need for an additional DSA examination