Vascular malformations of the brain

Interventional
Neuroradiology
Vascular Malformations
of the Brain
Mohamed M.A. Zaitoun, MD
Interventional Radiology Consultant, Zagazig University Hospitals, Egypt
FINR-Switzerland
zaitoun82@gmail.com
Interventional Radiology Unit,
Zagazig University, Egypt

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

Vascular Malformations of the Brain
a) Definitions of Arteriovenous Malformations
b) Classifications of Cerebral Vascular
Malformations
c) Capillary Telangiectasia
d) Venous Angioma
e) Cavernous Malformations
f) Brain Arteriovenous Malformations (BAVM)

a) Definitions of Arteriovenous Malformations :
-Definitions of arteriovenous malformation of the
central nervous system :
1-Doppman , 1971 :
-AVMs are tangled anastomoses of blood vessels
of varying caliber in which arteriovenous
shunting occurs in a central nidus (Latin, nidus ,
nest) , which is the area towards which one or
multiple feeding arteries converge , and from
which enlarged veins drain
2-Valavanis , 1996 :
-Cerebral AVMs are inborn errors of vascular
morphogenesis caused by a defect or
malfunction of the embryonal capillary
maturation process and resulting in the
formation of abnormal arterial , venous or
capillary channels with or without shunt

3-The Arteriovenous Malformation Study Group , 1999 :
-Brain arteriovenous malformations are a complex tangle of
abnormal arteries and veins linked by one or more
fistulas
-These are useful in setting out the component features on
which there is a consensus , i.e. arterial and venous
feeders , a nidus and arteriovenous (AV) shunting
-The last definition though , includes fistulas and therefore
AV connections without an intervening nidus , i.e. direct
arteriovenous fistulas (AVF)
-Thus , we can separate them from the definition of AVMs
only if the nidus is absent
-The 1996 Valavanis’ definition includes lesions without a
shunt
-So , the situation becomes more difficult and the process
takes us further away from a description of a ‘usual’
lesion

b) Classifications of Cerebral Vascular
Malformations :
-McCormick in 1966 defined five groups of
cerebral vascular malformations :
1-Capillary telangiectasia
2-Venous angioma
3-Varix
4-Cavernous angioma
5-Arteriovenous malformation
-All subsequent authors have based their
classifications on this and a more recent
representative example is that of Chaloupka
and Huddle :

1-Benign proliferating vascular anomalies :
Hemangioma
2-Nonproliferating vascular anomalies :
a) Capillary malformation (telangiectasias)
b) Venous malformation
c) Cavernous malformation (cavernoma)
3-Arterial malformation (angiodysplasia and
aneurysm)
4-Arteriovenous shunting malformation :
a) Brain AVM
b) Brain AVF
c) Dural AVM
d) Vein of Galen AVF
5-Mixed malformation

-This separates lesions that grow from those that
don’t , though it would be better stated as ‘don’t
general grow’ because examples of enlargement
of lesions in this group have been described
-This classification includes vascular tumors , as
proposed by Mulliken and a mixed lesion
category
-Thus , reflecting a shift towards considering
transitional lesions as a part of a continuum of
vascular developmental abnormalities

c) Capillary Telangiectasia :
1-Pathology
2-Etiology
3-Location
4-Radiographic Features

1-Pathology :
-The macroscopic appearance is of a small
collection of vessels on the cerebral surface
-Microscopically they are composed of thin-walled
capillaries without smooth muscle layers or
elastic lamina
-The surrounding brain is normal
-These lesions are usually diagnosed post mortem
and are typically found on the pial or immediate
subpial surface of the brain stem or pons

2-Etiology :
-This is unknown but multiple lesions occur in
hereditary hemorrhagic telangiectasia (HHT) or
Rendu-Osler-Weber syndrome , which is an
autosomal dominant disorder characterised by
multisystem vascular dysplasias in which those
affected develop multiple telangiectasias
-Telangiectasia occurs in the mucosa of the nose
and mouth , skin , lung and gastrointestinal tract

-Patients present with recurrent nosebleeds
or other episodes of bleeding
-The cerebral vascular abnormalities
associated with HHT include brain AVMs ,
cavernous malformations and aneurysms
-Cerebral lesions were found in 23% of HHT
patients screened for brain lesions by MRI

3-Location :
-Most occur in the pons , cerebellum & spinal cord
4-Radiographic Features :
a) CT :
-Is often normal
b) Catheter Angiography :
-Is often normal but may show faint vascular stain

Telangiectasia , vertebral angiogram showing a collection of small
irregular arteries on the left side of the brainstem , supplied by the
anterior superior cerebellar arteries

c) MRI :
-Seen as subtle lesions with no mass effect
T1 : Typically iso to low signal compared with brain
parenchyma
Gradient echo (GE) : Typically low signal
T2 : slightly increased signal intensity
T2* : low signal intensity (thought to be due to
deoxyhaemoglobin)
T1+C : may demonstrate ill-defined focal
enhancement

d) Venous Angioma :
1-Pathology
2-Etiology
3-Demographics , Natural History and
Clinical Presentation
4-Location

1-Pathology :
-The venous angioma or developmental venous
anomaly (DVA) is recognized as an abnormally
prominent collection of medullary veins which
drain to a single trunk
-The latter has , in the past , been termed a varix ,
but this term should be dropped since it is now
generally agreed that these lesions are caused
by abnormal venous development
-On microscopy they have a thin endothelium ,
with thin smooth muscle cell and elastic tissue
layers within a wall that is mainly composed of
collagen but may be thickened by hyalinization

2-Etiology :
-The conclusion that they are caused by a
development failure of a normal section of the
cerebral venous system is based on their having
been identified in neonates and their
nonprogressive behavior
-The initiating event probably occurs at about the
third week of intrauterine life during formation of
medullary veins
-A malconnection of deep and superficial veins
also occurs in Sturge-Weber syndrome , and
DVA may be a variation of the same failure of
normal development
-Crucially the DVA drains normal brain and
therefore should not be embolized

3-Demographics , Natural History and Clinical
Presentation :
-They are found in up to 2.5% of autopsies and are the
most common vascular abnormality of the brain
-They are rare causes of spontaneous hemorrhage
-Lifetime hemorrhage risk of 0.22%
-Other presentations are seizure , headache and transient
deficits
-They are increasingly recognized as incidental findings on
MRI , alone or in association with cavernous
malformations
-Since intervention isn’t indicated (except for the rare
situation of an emergency evacuation of hematoma) ,
their importance to the endovascular therapist is that
they are correctly diagnosed so that embolisation can be
avoided

4-Location :
-The most common locations are :
a) Frontoparietal region (36-64%) , usually
draining towards the frontal horn of the
lateral ventricle
b) Cerebellar hemisphere (14-27%) draining
towards the fourth ventricle
-However , DVAs can be seen anywhere ,
draining either superficially or deep

a) CT :
-Only enhanced scans may show linear vein
draining to ependymal lining of ventricle or
cortex with inverse umbrella-shaped (caput
medusa) leash of vessels draining towards
anomalous veins
-Medusa head seen on venous phase (hallmark)
-Dilated medullary veins draining into a large
transcortical vein

c) MRI :
-May be visible on most sequences, but is most
easily seen on postcontrast T1 sequences , If
there is an associated cavernous hemangioma
then susceptibility weighted sequences will be
most sensitive for this component
-SWI is the preferred sequence in venous
anomalies and proved to have better
detectability of venous structures than
conventional T2*-weighted imaging

DVA & a tiny cavernous malformation , (a) T1+C shows a subtle
curvilinear enhancing structure (yellow arrow) in the RT frontal white
matter representing a DVA , (b) Susceptibility weighted shows a
focus of susceptibility artifact (red arrow) , suggestive of an adjacent
cavernous malformation

Mixed vascular malformation , (a) T2 , (b) T1+C

e) Cavernous Malformations :
1-Pathology
2-Etiology
3-Demographics , Natural History and
Clinical Presentation
4-Location
6-Treatment

1-Pathology :
-These are hamartomatous lesions containing thin-
walled vessels with more circumscribed borders
than capillary telangiectasias and without
intervening normal brain
-There are no associated feeding arteries or veins
, so they are usually not detectable on catheter
angiography but are easily demonstrated by MR
scanning

-The macroscopic appearance is a capsulated blood-filled
tumor , resembling a grape
-On microscopy , they are composed of channels which
have an endothelial lining and thin fibrous adventitia
without elastin , smooth muscle cells or the other
elements of mature vessels
-They contain old hemorrhage , hemosiderin , calcification
or cholesterol crystals
-The walls may show hyaline thickening and the adjacent
brain gliosis
-Endothelial leakage causes microhemorrhages
-They can occur anywhere in the brain , but are most
frequently found in subcortical white matter ,
periventricular white matter , the pons and the external
capsule

2-Etiology :
-Sporadic and familial forms are recognized
-Multiple lesions probably always occur at some stage in
the familial disease , and they are found in at least 30%
of patients without a positive family history
-The genetic basis of the familial disease has been recently
linked to chromosomes 7 and 3
-The condition has an increased frequency in Americans of
Mexican descent , in whom a defective CCM1 gene has
been described
-Associations have also been described with capillary
telangiectasia , DVAs and previous radiotherapy
-There is increased risk of bleeding if a DVA is present ,
however , the DVA itself doesn’t have any bleeding risk

Presentation :
-There is no gender difference , and patients may
present at any age , but most do so in the
second to fourth decades
-Reported estimates of prevalence in the general
population are 0.5% at autopsy and 0.4% on
MRI
-They account for 5-16% of central nervous
system vascular malformations

-Asymptomatic cavernous malformations may
appear de novo and enlarge or regress on serial
MRI studies
-Symptoms are presumably initiated by
enlargement and these are , in descending order
of frequency :
Seizures , focal neurological deficit , headache and
hemorrhage
-Symptoms are often progressive , in a stepwise
fashion , and presentation is more commonly
due to hemorrhage in children and seizures in
young adults

When discussing rates of hemorrhage ,
symptomatic bleeding has to be distinguished
from the common asymptomatic hemorrhage
demonstrable on MRI
-Annual rates of symptomatic hemorrhage are 0.5-
0.7% , and asymptomatic bleeding rates are
higher , varying from5% to 23%
-Bleeding is usually intraparenchymal and only
rarely subarachnoid or intraventricular

4-Location :
-80% supratentorial
-Occur anywhere in CNS , common in Pons
a) CT :
-Isodense / Hyperdense (lesion due to calcification)
-Range in size from tiny (single focus of susceptibility
artifact) to giant
-Usually normal

(a) CT+C calcification is seen , (b) T2 shows the typical appearance of
this lesion and (c) gradient echo shows additional lesions because
of its sensitivity to blood breakdown products

c) MRI :
-T2 : Popcorn lesion : bright lobulated center with
black (hemosiderin) rim
-Subacute hemorrhage and degraded blood products
within the lesion produce a halo of signal
hyperintensity around the lesion on T1-weighted
images , a useful finding for differentiating
cavernous malformations from hemorrhagic tumors
and other intracranial hemorrhages
-Always obtain susceptibility sequences to detect
coexistent smaller lesions

Cavernoma in the postcentral gyrus on T1 , T2 and SWI ,
notice popcorn appearance and blooming artifact

T2 & T2* gradient echo show multiple cavernomas , notice the popcorn
appearance with peripheral rim of hemosiderin on the T2 , the lesions are
almost completely black on the gradient echo due to blooming artefacts ,
T2* and susceptibility weighted imaging (SWI) markedly increase the
sensitivity of MRI to detect small cavernomas , the five black dots in the left
cerebral hemisphere on the T2* are also cavernomas and are not visible on
the T2WI

(a) Axial T2 shows a large left parietal mass that resembles a popcorn ball with
a hypointense hemosiderin rim (arrows) and loculated hyperintense
compartments
(b) Axial T1 at the same level shows multiple high signal intensity
compartments in the lesion , findings suggestive of subacute hemorrhage ,
a faint halo of high signal intensity also is visible around the lesion
(arrowheads)

Cavernous malformation & associated DVA , T1+C show a hypointense ,
centrally hyperintense nonenhancing cavernous malformation (yellow
arrow) in the left cerebellar hemisphere , directly superior to the cavernoma
(b) is an enhancing vascular structure with caput medusa morphology (red
arrow) representing a DVA

Giant cavernous malformation (a) CT without contrast shows a
hyperattenuating complex mass (arrows) in the RT fronto-temporal lobe , (b)
T1 shows the mass is predominantly cystic & hyperintense (representing
blood products) , (C) FLAIR shows that the intracystic contents are primarily
hyperintense , there is a complete low signal hemosiderin ring surrounding
the lesion (red arrows) , there is mild surrounding edema , (d) T1+C shows
no appreciable enhancement

6-Treatment :
-Since there is no endovascular access , these
lesions are not referred to the endovascular
therapists for treatment
-Management is generally conservative and
intervention reserved for symptomatic lesions
-Interventions are surgical resection , which is
generally reserved for symptomatic large
accessible lesions , or focused radiotherapy
-Reports of the effectiveness of radiotherapy have
been mixed , and its use in this condition
remains controversial

f) Brain Arteriovenous Malformations (BAVM) :
1-Pathology
2-Classification
3-Etiology
Presentation
5-Location
7-Proliferative Angiopathy
8-Grading System
9-Management

1-Pathology :
-A vascular lesion composed of an abnormal tangle of
vessels (nidus) with pathologic shunting of blood flow
from the arterial to the venous tree , without a normal
intervening capillary bed
-The macroscopic findings are of a variety of vessels
ranging from well-differentiated arteries and veins to
highly malformed , hyalinized , poorly differentiated
vessels with thick or thin walls
-The abnormal vessels are variably dilated (and may form
saccular aneurysms) or narrowed with segmental or
focal areas of stenosis

-Microscopy of arteries shows the endothelium and elastic
layers are irregular with vacuolisation and necrosis of
smooth muscle cells , invasion of the adventitia by
foreign cells and small blood vessel as well as changes
in the mural matrix
-Aneurysms presumably develop in areas where the elastic
tissue and smooth muscle is thin or absent
-In some areas , the vessel walls are thickened by medial
hypertrophy , collections of fibroblasts and thickening of
the basal lamina and interstitial tissue
-These changes are presumed to be induced by high blood
flow and shear stress
-The nidal vessels are indeterminate as either artery or vein
, and sclerotic brain tissue is found between the vessels

-One final point on the macroscopic appearance of lesions
and their location is the effect of a low pressure , high
blood flow shunt on adjacent vessels
-Superficial lesions are not infrequently supplied by
transpial arteries , which are generally considered to be
a recruited collateral supply , but this supposition needs
to be confirmed from longitudinal observational data ,
which currently remains incomplete
-Another ‘collateral’ pattern which is presumed to be
induced is angiomatous change in arteries adjacent to
the nidus
-These vessels though tortuous and appearing similar to
those of the nidus should not be confused with them
because they show normal contrast transit times on
angiography
-Cure of the AV shunt leads to their disappearance , but
our understanding of their etiology and the underlying
haemodynamic factors is incomplete

2-Classification :
a) Valavanis and Yasargil
b) Lasjaunis , Berenstein and Ter Brugge

a) Valavanis and Yasargil :
-Valavanis and Yasargil developed a system based on the
principle location of nidal vessels
-This divides superficial BAVMs into :
1-Sulcal (nidus located in the subpial space within a sulcus)
2-Gyral (nidus completely surrounded by a cortical mantle)
3-Mixed sulcal-gyral lesions
-Deep lesions are found in :
1-The subarachnoid space (within basal cisterns or
fissures)
2-The parenchyma (within deep nuclear structures)
3-The ventricle (originating in choroid plexus)
4-Individual lesions can involve one or more of these
compartments , i.e. mixed

b) Lasjaunis , Berenstein and Ter Brugge :
-An alternative system proposed by Lasjaunis , Berenstein
and Ter Brugge
-Recognizes similar deep and superficial locations but
emphasises the role of the feeding pedicles
-Thus lesions confined to cortex are defined as being
supplied exclusively by cortical arteries and veins whilst
subcortical lesions are supplied by cortical arteries but
may drain to both superficial and deep veins
-Cortico-ventricular BAVMs are supplied by both perforator
and cortical arteries and drain to superficial and deep
veins
-This classification separately defines a cortico-callosal
BAVM as not being supplied by perforated arteries and ,
like Valavanis and Yasargil , choroid and deep BAVMs
with centrally directed (deep) venous drainage

3-Etiology :
-The majority of lesions are thought to be
‘congenital’ rather than acquired
-Implicated acquired causes are trauma (which
includes surgery) and ionizing radiation , but the
links are vague
-AVMs have been reported to have developed in
previously normal (on imaging) brain , and the
vast majority of patients don’t give a positive
family history

Presentation :
-Brain AVMs are rare lesions
-Brain AVMs affect men and women equally
-The commonest age at diagnosis is consistently
reported as between 20 and 40 years
-Most patients present after spontaneous
intracranial hemorrhage or the onset of seizures
-The relative rates are 50-60% with hemorrhage
and 25-30% with seizures

-About 10% have focal neurological symptoms or
signs without hemorrhage , and a small
proportion (3-5%) present with migraine or other
types of headache
-In children (<16 years) , bleeding is the most
common presentation and accounts for 30-50%
of hemorrhagic stroke in this age group
-Epilepsy also tends to present in younger patients
: 44% in the second decade , 30% in the third
decade and only 6% in the 30-60-year age
group

-Though focal neurological deficits as a presenting feature
are uncommon , subsequent progressive neurological
deficits are common in patients on observation and
usually attributable to the effects of spontaneous
hemorrhage
-Observational studies of untreated AVMs have estimated
an annual rate of hemorrhage of 2-4% per annum
-Patients presenting with hemorrhage were found to have
an increased risk of subsequent hemorrhage compared
to patients presenting without hemorrhage
-The risk of bleeding is approximately 2% per year after
diagnosis without hemorrhage and up to 18% in the fi rst
year after a presenting hemorrhage

5-Location :
-The nidus of BAVMs occurs in
supratentorial brain (85–90%) or the
cerebellum (10–15%) and involves
superficial (70%) or deep (30%) structures
of the brain
-They vary in size from micro-AVM (<1 cm)
to large lesions (>6 cm)

a) CT :
-Hyperdense enlarged serpiginous vessels
-Often speckled calcification (25 %)
-Enhance strongly
-Gold standard for assessment of morphology and nidal
architecture including presence of associated arterial or
venous aneurysms (10 %) , varices and stenosis
-The diagnostic criteria include :
1-Nidus embedded within the brain parenchyma
2-Early venous drainage , if the veins are seen in the
arterial phase

Left occipital arteriovenous malformation (AVM) with multiple calcified
phleboliths and numerous hyperattenuating vascular channels

CT+C shows a tangle of intensely enhancing tubular structures
embedded in the left parietal lobe , a finding that is compatible with a
nidus , hyperattenuation representing intraventricular hemorrhage is
noted in the ventricles

Lateral left internal carotid angiogram reveals a glomerular type nidus
in a cortical location supplied mainly by the posterior parietal and
angular branches of the left MCA with early drainage into a left
parietal cortical vein , findings that confirmed the diagnosis of a brain
AVM

Sulcal brain arteriovenous malformation , the lesion lies in the posterior
temporal lobe and is shown on internal carotid angiograms as the
nidus starts to fill (a) and after shunting to cortical vein (b) The
arrows on (b) indicate veins

Brain arteriovenous malformation , this typical wedge shape is seen in
arteriovenous malformation which extend into white matter and may
drain to both superficial (cortical) and deep cerebral veins , ICA DSA
in the frontal projection

Brain AVM of the corpus callosum , the malformation is supplied by the
pericallosal artery and an enlarged lenticulostriate artery (arrow) , seen on
the frontal view (a) , the malformation drains to a massively enlarged
internal cerebral vein (arrowheads) and a cortical vein on the medial surface
of the frontal lobe (double arrows) shown on the lateral view (b)

c) MRI :
-Serpiginous black flow voids
-May be evidence of local atrophy and gliosis (as a result of
vascular steal and ischemia) or previous hemorrhage
-AVM replaces but does not displace brain tissue (i.e. mass
effect is uncommon) unless complicated by hemorrhage
and edema
-Edema occurs only if there is recent hemorrhage or
venous thrombosis with infarction
-There are usually adjacent changes to the adjacent brain
including gliosis (T2 prolongation) , dystrophic
calcification & blood products (blooming T2* gradient
imaging) , the gliosis / encephalomalacia or
mineralization seen in the adjacent brain is due to
alteration in vascular flow from the AVM
-Phase contrast MR angiography is often useful to subtract
the hematoma components when an AVM complicated
by an acute hemorrhage needs to be imaged

T1 shows large occipital arteriovenous malformation (AVM) with parasagittal
flow void

T2 showing numerous flow voids

7-Proliferative Angiopathy :
a) Incidence
b) Clinical Picture
c) Radiographic Features

a) Incidence :
-Cerebral proliferative angiopathy ,
previously known as diffuse nidus type
AVM , is present in an estimated 2%-4%
of all brain AVMs
-There is a female predilection of 2:1 with a
rather young mean patient age (20 years)

b) Clinical Picture :
-Progressive neurologic deficits , transient
ischemic attacks , seizures and
headaches are the common presenting
symptoms with hemorrhage being
extremely rare

c) Radiographic Features :
1-CT & MRI :
-The typical MR imaging and CT findings
include a proliferative type nidus in which
normal brain parenchyma is
interspersed between the abnormal
vessels
-Often an entire lobe or even brain
hemisphere is affected

(a) PD , (b) T1+C show multiple flow voids and contrast-enhanced
tubular structures representing a large vascular lesion that involves
the entire right cerebral hemisphere , the normal brain parenchyma
is interspersed between the abnormal vessels

2-Catheter Angiography :
-The nidus is fed by multiple arteries (absence of a
dominant feeder)
-The arterial feeder vessels tend to be of normal size
or only moderately enlarged , associated stenosis of
the feeder vessels are often identified
-Classical nidus appearance with scattered “puddling”
of contrast which persisted into the late arterial and
early venous phase
-There is extensive transdural supply to normal and
abnormal brain tissue through branches of the ECA
-The lack of clear early venous drainage on dynamic
images is the key to differentiating this disease from

(a-c) FLAIR ,(d) T1+C and angiography (right ICA (f) , (e) left ICA (3D) , (g) AP , and (h)
lateral view , (i) left ECA in a 15-year-old male with recurrent seizures , disabling
headaches and transitory ischemic attacks , a diffuse network of densely enhancing
vascular spaces can be seen throughout the frontal lobe , compared with the size of
the nidus , there is paucity of draining veins and no dominant feeders can be
identified , transdural supply testifying for the proliferative nature of the disease can
be seen

CT (precontrast in (a) & (b) , with contrast C-d) and angiography (right ICA) frontal view
(e) and lateral view (f) and left vertebral artery in frontal (g) and lateral views (h) in a
22-year-old male patient with recurrent intense headaches and transitory ischemic
attacks , there is dense contrast enhancement of the lesion and paucity of draining
veins in comparison to the nidus size , during angiography , no dominant feeders can
be identified and there is scattered “puddling” of contrast material in the nidus with
capillary ectasias , in the occipital lobe neoangiogenesis can be perceived

(a-c) Angiography in frontal views , early arterial , late arterial and early venous phase of
the right ICA, (d) left ICA , (e) left ECA , (f) left vertebral artery , (g) 3D rotational
angiography , In the early arterial phase the absence of dominant feeders and the
equal contribution of many different arteries can be well perceived , the contrast
dynamics reveal persistence of contrast material in the malformation and no early
venous drainage , transdural supply testifies for the proliferative component of the
disease whereas injection into the vertebral artery demonstrates diffuse
neoangiogenesis in other cortical areas

Fifteen-year-old boy with epilepsy , angiography of the right ICA in the arterial and
venous phase (a,b) lateral views , (c,d) frontal views , MRI (T1 precontrast , e,f), and
frontal views of the left ICA (g) and right vertebral artery (h) reveal a fuzzy appearing
nidus with interspersed brain in the left basal ganglia , a mild stenosis of the right
distal ICA and diffuse neoangiogenesis in the parietooccipital areas , within the nidus
angioectasias are present , the venous drainage is slightly too early , however no
areas of high-flow shunting can be perceived

Two different patients with right frontoparietal proliferative angiopathy
with similar stenoses on the proximal M1 segment (arrows)

(a) AP RT ICA angiogram shows relatively normal-sized MCA branches and
lack of early venous drainage , findings that confirm the diagnosis of
proliferative angiopathy , stenosis of the proximal M2 segment of the right
MCA just distal to the MCA bifurcation is also noted (arrow) , (b) Lateral RT
ECA angiogram shows an extensive transdural supply to the right cerebral
hemisphere via the branches of the middle meningeal artery

8-Grading System : (Spetzler's Criteria)
3210
--YesNoEloquence
--DeepSuperficialDraining vein
>6 cm3-6 cm<3
cm
-Size

-Higher score is associated with higher chance of
hemorrhage
-Other factors associated with poorer prognosis /
higher risk of hemorrhage :
1-Intranidal aneurysm
2-Aneurysm in the circle of Willis
3-Aneurysm in arterial feeder
4-Venous stasis

-Eloquence of adjacent brain :
a) Eloquence brain :
-Sensorimotor , language , visual cortex ,
hypothalamus , thalamus , brain stem ,
cerebellar nuclei or regions directly
adjacent to these structures
b) Non-eloquence brain :
-Frontal and temporal lobe , cerebellar
hemispheres

9-Management :
a) Prognosis and Risk of Hemorrhage
b) Angioarchitecture
c) Treatment

a) Prognosis and Risk of Hemorrhage :
-It is now generally accepted that patients
presenting with hemorrhage are at greater risk
of re-bleeding in the short term and that each
hemorrhagic event causes death or permanent
disability to some of them
-Without surgical treatment , the risk of death was
29%, risk of hemorrhage 42% , risk of
neurological handicap 27% and risk of epilepsy
18% during a mean follow up period of 10.4
years for symptomatic AVM

b) Angioarchitecture :
-Identifying the site and vessels supplying a
BAVM is obviously crucial to management
-Traditionally this has depended on catheter
angiography (DSA) , but several authors
have emphasized the additional value of
superselective angiography (i.e. injection
of individual particles) to the definition of a
lesion’s angioarchitecture

-We now have the option of improved planar
imaging for angiography using MRA or CTA
-Multimodality imaging (e.g. MRA/CTA/Flat
Detector CT) and reconstructions of 3D data
with image fusion techniques can reliably
separate arteries and veins from nidal vessels
-Additionally , MR techniques , such as phase
contrast sequences and arterial spin labelling ,
can interrogate blood flow patterns and
pathways within the nidus

*Identification of Prognostic Features :
-Four features are particularly important :
1-Arterial ‘flow’ aneurysms
2-Intranidal aneurysms
3-Nidal size
4-Location

1-Arterial ‘flow’ aneurysms :
-These are probably only relevant if they arise from
hypertrophy arteries directly supplying the nidus
-Aneurysms found remote from arterial pedicles should be
considered coincidental and be managed in the same
way as unruptured aneurysms in patients without an
AVM
-The decision to treat a pedicle ‘flow’ aneurysm depends
firstly on whether it is considered the cause of a
presenting (subarachnoid) hemorrhage and secondly
whether it affects access to the nidus for endovascular
treatments
-A general principle is that if the nidus is successfully
obliterated then pedicle aneurysms will probably regress
and / or be at less risk of spontaneous rupture

2-Intranidal aneurysms :
-The reported frequency of aneurysmal dilatations
, saccular aneurysm and pseudoaneurysms
within the nidus varies from 10% to 40% and
largely depends on how assiduously they are
sought and whether superselective angiography
is performed
-What is clear is that identification of intranidal
aneurysms from 2D DSA is imprecise and
superselective angiography has been advocated
because it improves their detection rates
-After acute bleeding , a demonstrated intranidal
pseudoaneurysm represents a target for early
embolisation since it may enlarge and rebleed in
the short term

AVM with intranidal aneurysm , the images show an internal carotid
DSA (a) and an unsubtracted image showing the aneurysm caste
with Onyx (b) , CT angiography (not shown) demonstrated bleeding
from this aneurysm

3-Nidal size :
-Micro-AVMs (<1 cm) and small BAVMs (<2 cm)
are generally considered at high risk of
rebleeding but this assumption may be
observational since small lesions are unlikely to
cause symptoms other than hemorrhage
-They are also more likely to have a single arterial
supply
-Occult intracerebral bleeding is sometimes
attributed to a micro-AVM which has
spontaneously obliterated itself in the process

Microarteriovenous malformation , a small brain AVM is seen on the
lateral internal carotid DSA (a) in the cortex of the inferior frontal
lobe , the superselective angiogram (b) shows two draining veins
which are marked with arrows on (a) and fill because of shunting
through the nidus

4-Location :
-The influence of location on prognosis is complex
-Deep and periventricular locations imply deep
venous drainage and the involvement of
perforator artery feeders
-So a number of poor prognostic features may
contribute to their reported higher rate of
rebleeding
-Posterior fossa lesions may or may not have
higher risks of bleeding but the morbidity caused
by hemorrhage is greater than for supratentorial
lesions , so intervention is generally
recommended for unruptured lesions on the
basis of location alone

-Location can also sometimes be related to
the symptoms a BAVM causes , e.g.
seizures are common with temporal lobe
located lesions and visual disturbance ,
with AVMs in the occipital lobe
-The presence of a recruited transpial blood
supply from scalp arteries , in some cases
, may be the cause of cranial pain

*Influence of Angioarchitecture on Selection of
Treatment Method :
-Planar scanning (without the need for catheter
angiograms) often provides sufficient information
to identify the anatomical features used to select
patients for particular treatment methods , i.e.
stereotactic radiotherapy , surgical resection or
embolisation
-The size of the nidus is related to the
effectiveness of radiotherapy and results are
best for lesions less than 10-12 cc in volume
-Size , position and venous drainage are
recognized as features correlating with
outcomes after surgical resection

-Spetzler and Martin grading system is commonly
employed (see before) :
1-Good surgical results can be expected when
lesions with Grades 1-2 are resected
2-Intermediate outcomes at Grade 3
3-Higher complication rates in operations for
Grades 4-5 BAVMs
-Its merit lies in its simplicity but it fails to recognize
patient variables such as age , gender and
symptoms , which obviously are factors in
treatment selection

-Angiographic features are important in deciding
whether endovascular treatment is feasible or
appropriate
-The number of arterial pedicles , their size , the
presence of ‘en passant’ arteries and the
eloquence of adjacent areas are all factors to be
considered
-An angiographic assessment should also assess
for collateralization from transpial arteries which
may indicate previous hemorrhage and increase
the risk of vessel tearing during catheter
withdrawal

-Angiomatous changes in adjacent arteries (identified as
separate from the nidus by their normal contrast washout
rates) , stenosis which may induce ‘moyamoya’-like
collateral arteries and evidence of venous hypertension
which is a poor prognostic feature (and would favour
intervention) should all be assessed
-Functional testing for ‘at risk areas’ of eloquent brain by
superselective injection of barbiturate is generally not
employed because of its logistical difficulties and mixed
reports of its efficacy
-Noninvasive functional testing using fMRI is now a useful
alternative for identifying eloquent adjacent structures,
e.g. language area , and advising patients about the risk
of intervention

*Treatment planning :
-For endovascular treatment planning a variety of
angiographic features are important such as :
1-The size and number of arterial pedicles
2-Presence of large arteriovenous shunts
3-Availability of access arteries or veins
-3D angiograms , particularly CTA , can be used to
assist the interpretation and often allows a
correlation between sites of bleeding and
identified aneurysms

-3D rotational angiography currently gives
the best possible resolution and enables
the operator to build up a detailed picture
of the angioarchitecture
-A fundamental role of pretreatment imaging
is to identify aneurysms and , if patients
present after hemorrhage , to correlate
them with the site of bleeding

c) Treatment :
-The principle aim of treatment is to eliminate the
lifelong risk of hemorrhage
-The assumption underlying any form of
intervention is that complete obliteration /
removal of the BAVM means that the patient is
no longer at risk of future hemorrhage
-Incomplete treatment risks recurrence and future
bleeding
-The effects of anatomical cure on other symptoms
are less certain
-Obviously the risk : benefit balance of intervention
must favour treatment

1-Medical Management
2-Surgical Resection
3-Radiotherapy
4-Embolisation

1-Medical Management :
-Observation of asymptomatic lesions , given the low risk of
hemorrhage in the short term , is generally accepted in
patients with no angiographic features associated with a
higher risk of bleeding
-There are currently no universal guidelines on which to
base these decisions (hence the rationale for
randomization in ARUBA) nor agreed protocols for
imaging surveillance
-Medical management for the control of symptoms :
1-Headache
2-Epilepsy

2-Surgical Resection :
-The goal of microsurgical resection is complete removal of
the nidus in a one stage operation
-This objective may require preoperative embolisation to
reduce the size of larger lesions and facilitate surgery
-Indications for Surgical Resection :
*When AVMs are diagnosed , the selection of patients for
surgical resection is based on an assessment of surgical
risk and likelihood of success
*This depends on the available surgical expertise , Spetzler
and Martin grading criteria , patient specific factors and
an analysis of the angioarchitecture
*In all but the emergency situation this process involves
multidiscipline consultations

-Surgical selection criteria :
1-Maximum nidus size (best estimated by MRI
and DSA)
2-Venous drainage :
-The Spetzler and Martin grading system defines
deep veins as those not accessible at
craniotomy
-This is different from the anatomical definition of
drainage to deep rather than superficial cerebral
veins
-Thus , interhemispheric cortical veins are
considered deep because they are difficult for
the surgeon to access during resections

3-Eloquent areas :
-These are the sensorimotor cortex , Broca’s area
and occipital cortex , deep nuclei of the
brainstem and cerebellum , thalamus ,
hypothalamus , internal capsule and cerebral
and cerebellar pedicles
-In this definition, cortical structures are assumed
to maintain their normal functional
representations , but this may not be the case in
AVM patients , and functional testing (by fMRI)
may help to refine the analysis of operative risk

4-Patient factors :
-These include age , gender , medical comorbidity
, the patient’s occupation and the possible
consequences of any iatrogenic disability on
their lifestyle
5-Angiographic features :
-In addition to an assessment of features identified
to increase the risk of bleeding , an analysis of
the angioarchitecture may suggest the cause of
symptoms such as epilepsy (i.e. an enlarged
cortical vein) or headache (i.e. enlarged dural
arteries)

*Surgical Indication and Modes of
Presentation:
-The mode of presentation influences the decision
to intervene , thus :
1-Acute hemorrhage :
-Emergency evacuation of hematoma and BAVM
resection may be lifesaving
-Postoperative angiography is mandatory to show
the extent of the resection and embolisation , or
radiotherapy may be appropriate to manage any
residual

2-Symptomatic patients with previous hemorrhage :
-Generally intervention is recommended , and its form will
be dictated by the above surgical selection criteria
3-Asymptomatic and symptomatic patients without previous
hemorrhage :
-Resection is performed when the surgical risk is judged
lower than the natural history and therefore generally
only for patients with Spetzler and Martin Grades 1-2
lesions , in this situation , radiosurgery alone may be
indicated
-For patients with Grade 3+ lesions, preoperative
embolisation may be appropriate

*Surgical Results :
-For low Spetzler and Martin grade lesions (Grades 1 and
2) , the reported complete resection rates are excellent
at 90-100%
-For high Spetzler and Martin grade lesions (Grades 4 and
5) , complete cure is only possible in a small minority
(5%) and should only be attempted in patients with
history of recurrent hemorrhage or existing neurological
deficits
-Most patients with large lesions are not treated surgically
and if they are it is combined with radiotherapy and / or
embolisation
-Partial surgical resection is generally performed (ca. 20%
of Spetzler’s series) only if symptoms are progressive
-Surgical resection is reasonably effective at curing
epilepsy with 40-80% cure rates in patients with a history
of seizures

*Surgical complications :
-Reported rates of complications after
microsurgical resection of small , i.e. <3 cm
AVMs (Spetzler and Martin Grades 1-2) are low ;
0-5% morbidity and 0-4% mortality
-Operative complication rates rise dramatically for
surgery of larger lesions
-Outcomes after surgical resections of Spetzler
and Martin Grades 4 and 5 lesions have been
reported as morbidity rates of 12-22% and
mortality rates of 11-38%

*Complications after surgery are due to :
1-Cerebral edema and swelling (up to 3%) due to
normal perfusion pressure breakthrough and
hyperaemia induced by an acute alteration in
regional hemodynamics
2-Early rehemorrhage (2%)
3-Vasospasm of arteries exposed during surgery
(1%)
4-Thrombosis of arterial or venous ‘stumps’
associated with large vessel ligation

3-Radiotherapy :
-Radiotherapy (or radiosurgery) is performed using
a focused high dose of ionizing radiation (12–25
Gy) delivered (usually in a single dose) to the
nidus in order to induce vessel wall thickening
and vessel occlusion
The Gamma knife system (Elekta AB, Sweden)
focuses multiple beams of gamma radiation
using a multiport helmet that surrounds the
patient’s head and protects all but the selected
tissue volume from a cobalt-60 radiation source ,
adapted conventional radiotherapy units can
also be used

-Radiation-induced damage is primarily to
the vessel endothelium and smooth
muscle cells
-It induces an inflammatory reaction which ,
when healed , causes vessel narrowing
and nidal obliteration
-The process takes ca. 24 months.

*Radiotherapy Results :
-Complete obliteration rates of 75-95% are
reported for small AVMs (<3 cm maximum nidus
dimension)
-For larger lesions , the cure rate is much lower ,
and in general , larger lesions are not treated
-However , recently there has been interest in the
use of fractionated treatments and
improvements in dose delivery techniques
allowing treatment of larger lesions
-Single-dose treatment can be repeated after 3
years if the lesions fail to occlude

*Complications :
-It is assumed that the latency between treatment and
observed obliteration of nidal vessels means that
patients are not protected against spontaneous
hemorrhage
-Bleeding during this period certainly occurs but not at an
increased rate relative to natural history estimates
-In fact , there is some evidence for a partial protecting
effect during the latent period after treatment and before
anatomical cure is complete
-Reported permanent neurological deficits in 4.8% and an
overall neurological complication rate of 8% , radiation
injury in the adjacent brain was identified in 6.4% of
treated patients , the frequency is directly related to size
of the radiation dose and treated volume

4-Embolisation :
-Embolisation is used alone or as an adjuvant treatment
combined with surgery or radiotherapy
-The goals of treatment are different if it is attempted for
complete cure , to facilitate surgery or radiotherapy or
used as palliative treatment
-Its role , in the multimodal management of brain AVMs
depends , to some extent , on where you work
-In many countries embolisation is performed as the initial
intervention for BAVMs for a variety of ‘unscientific’
reasons such as lack of alternative expertise ,
unavailable resources and because of patient preference
-Whereas in others , its role is primarily as a presurgical or
preradiotherapy adjunct treatment
-Even within national borders , the relative availability and
appetite of local specialists is expressed in how it is
deployed in practice

-The introduction of cyanoacrylate agents , i.e. N-
butyl-2-cyanoacrylate (n-BCA) , was delayed in
the USA until the completion of a randomized
controlled trial showing its equivalence to the
injection of polyvinyl alcohol particles
-Ethylene vinyl alcohol copolymer was introduced
in 1990 but used almost exclusively in Japan
until it was formulated and marketed as Onyx
(ev3 Endovascular Inc. Irvine, CA USA) , Its use
involves a different delivery technique with
longer injections of larger volumes of liquid

*Embolisation Results :
-These have to be separated by the aims and
indications for the treatments
-These are sometimes not clear from series
reports which limit the definition of success to %
nidal volume reduction
-Criteria for assessing embolisation are :
1-Complete Obliteration
2-Partial Treatment
3-Relief of Symptoms

1-Complete Obliteration :
-Published results (largely small single
centre series) show a relatively low cure
rates for AVMs managed by embolisation
alone in the 1980s and 1990s
-These may reflect the fact that the most
easily cured are those that can also be
resected or treated by radiotherapy

2-Partial Treatment :
-Objective assessments of the effect of partial embolisation
are difficult
-One method is to count success as preparing an
inoperable / untreatable lesion for adjuvant treatment
-If pre-surgery , the conversion is one factor
-Another , is the more subjective value of whether
embolisation facilitated the resection
-This can be evaluated by a reduction in anticipated blood
loss during surgery
-For preradiotherapy , the conversion relates to volume
reduction
-So success is measured by reductions in size , which is
logical if treatment is performed to reduce the size of
BAVMs to below a 12-14-cc volume threshold

3-Relief of Symptoms :
-Embolisation has been reported as
successful in reducing neurological
symptoms attributed to the ‘steal’ affect on
adjacent brain blood flow

*Complications :
-Reported complication rates vary from permanent
morbidity in 2-4% and mortality in 1-4% of
patients
1-Procedural complications are those associated
with catheterization of small cerebral vessels ,
e.g. perforation or rupture of flow aneurysms , or
due to the inadvertent occlusion of normal
arteries
2-Use of adhesive embolic agents risks causing
catheter retention or tearing of vessels on
catheter removal
3-Pulmonary embolism due to emboli reaching the
lungs is also reported

4-The most devastating complication is provoked
bleeding of the AVM , which may occur acutely
or be delayed :
-Acute post-embolisation hemorrhage is often
difficult to explain in individual cases but is most
often caused by spread of embolic agent to
draining veins
-Delayed bleeding may occur in association with
the occlusive hyperaemia syndrome or normal
perfusion pressure breakthrough , progressive
thrombosis of draining veins may occur after
embolisation and contribute to the occlusive
hyperaemia syndrome

Vascular malformations of the brain

Vascular malformations of the brain

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