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SPINAL AVM – CLASSIFICATION
Spinal Cord Vascular Malformations
It represent a heterogeneous group of non-neoplastic vascular
Spinal arteriovenous malformation (AVM) is an abnormal
tangle of arteries and veins in which the arteries feed directly
into the veins with abnormal intervening capillary bed.
AV fistula (AVF): direct communication between artery & vein
AV malformations (AVMs): multiple complex communications
Nidus: the core of an AVM that appears angiographically and
anatomically as a conglomeration of vessels because of the
superimposition of arteries and veins.
Rare cause of neurologic dysfunction
5% of all intraspinal pathology
Occur throughout the spine
Affect any age group, majority: 30-50
Better diagnosis and management with improved
techniques of spinal angiography, MRI, MRA
and endovascular surgery
O`Toole and McCormick. Chapter 83: Vascular Malformations of the Spinal Cord.
Rothman-Simeone The Spine. 5th Edition
HISTORY AND CLASSIFICATION
Classification of spinal AVM has evolved with the
technology available to study them.
Earliest studies were based on postmortem examinations.
1888, Gaupp described them as “hemorrhoids of the pia
In 1914, Charles Elsberg performed the first successful
operation on a spinal cord AVM.
1925 – Sargent: classified 19/21 cases as venous angiomas
1943 – Wyburn Mason classified AVMs into histological
groups arteriovenous angiomas and purely venous
Baker –layton in 1967 classified AVM s into 3
Type 1 - single coiled vessel type
Type 2 - Glomus AVM
Type 3 - juvenile AVMs
• 1977 – Kendall and logue identified AVFs in the
dural sleeve of spinal nerve roots which were
consistent with single coiled vessel type of
HISTORY AND CLASSIFICATION
HISTORY AND CLASSIFICATION
Two additional advances in the last 25years
1977 – Recognition by Djindjian that some
intradural lesions that were previously
considered AVMs of the spinal cord are actually
simple AVFs in the pia(Perimedullary AVFs)
Recognition of cavernous angiomas
Classification: Berenstein A(1999)
Spinal cord vascular malformation
Isolated - AVMs and Av fistulas
Multiple – Metameric (Cobb syndrome and other
associations) and non metameric (Rendu –Osler
– weber syndrome)
• Spinal cord telangiectasias
Classification: Anson, Spetzler(1992)
Most widely accepted. 4 types
Type 1: AV Fistula located between a dural
branch of the spinal ramus of a radicular artery
and an intradural medullary vein
Type 2 : Intramedullary glomus malformation
with a compact nidus within the substance of the
Type 3: Juvenile or combined AVMs -extensive
AVM often extending to the vertebra or
Type 4 : Intradural perimedullary arteriovenous
A – simple fistula fed by a single arterial
B – Intermediate sized fistula with multiple
dilated arterial feeders
C – Large perimedullary fistula with multiple
giant arterial feeders.
Classification: Anson, Spetzler(1992)
1. Anterior spinal artery:
Arises from the fusion of a contribution from each of the vertebral
Supplies the ventral 2/3 of the cord
Important contribution to the ASA is from the artery of Adamkiewicz,
which may arise anywhere from T8 to L1, more often on the left side.
The anterior spinal axis in the anterior commissure of the spinal cord
and gives rise to perforators throughout its length.
2. Paired posterior spinal arteries:
run the length of the spine
supply the posterior 1/3 of the cord
3. At each segmental level: a dorsal ramus of the
segmental artery enters the intervertebral foramen and
gives rise to 3 branches:
Dural branch: to dura
Radicular branch: to nerve root
Augments the flow to the anterior spinal artery
During the 3rd stage of fetal development, most of the medullary
branches involute distal portion of the cord relatively ischemic
Somewhere between T8 & L2, especially on the left: the
medullary branch does not involute and becomes the artery of
Coronal venous plexus:
A plexus on the cord surface
Formed by coalescence and anastomosis of radial veins
Epidural venous plexus:
At segmental levels, medullary veins leave the coronal plexus
and exit the intervertebral foramen to join the epidural plexus
The plexus communicates with the venous sinuses of the
It drains into the ascending lumbar veins and the azygous
Pathophysiology of Symptoms
Depends on the type of the AVM
Mechanical compression of the spinal cord and
The clinical signs are due to:
(3) steal into AVF/AVM;
(4) venous hypertension;
(5) thrombosis of draining vein,
(6) pressure of aneurysm, venous or arterial, true or false;
(8) syringomyelia and
(9) Foix-Alajouanine syndrome, a result of chronic venous
ischaemia of the spinal cord.
Type I (Dural AV Fistula)
The most common type
60% of spinal AVF/AVM
Single AV connection within the
dura of the nerve root sheath
Results in dilated arterialized
coronal venous plexus
Dural AV Fistula
Spinal Dural Arteriovenous Fistula
Represent at least 35% of all spinal vascular
malformations in large series, although some estimates
range as high as 80%
Most commonly occur at thoracolumbar levels, usually
between T5 and L3
It represents an AV shunt that occurs within dural
covering of spinal cord, below and medial to the pedicle.
Located adjacent to intervertebral foramen or within
dural root sleeve, with arterial supply arising from dural
branch of radicular artery.
An intradural vein drains the shunt directly into the pial
veins of the cord J Neurosurg 1983;59:1019-1030.06-Jan-16
AV shunting result in venous engorgement and
venous hypertension involving the spinal cord
(Venous congestion, steal phenomenon, ischemia
Most often, no direct arterial supply to the spinal
cord itself originates from the radicular artery
feeding an SDAVF.
In 10% to 15% of cases, however, SDAVF is fed
by a radicular artery that also supplies spinal cord
via a radiculomedullary or radiculopial branch
Most common spinal vascular anomaly in older adult, afflicts males
in 80% to 90% of cases
Presents after the fourth or fifth decade;
Chronic progressive myelopathy leads to progressive lower extremity
weakness, often characterized by both UMN & LMN signs.
Localized or radicular back pain, bowel, bladder, and sexual
dysfunction -Often exacerbation by excersise
Claudication pain is a common presentation in dural AVF.
Claudication pain and neurological deficit may be worsened by a
Lead to paraplegia within 2 – 4 years.
15% of the patients have rapid neurological worsening and is called
Foix alajouanine syndrome and is due to venous congestion and
should be treated immediately 06-Jan-16
Anteroposterior (A) and lateral (B) lumbothoracic spine radiographs reveal
medial erosion of the pedicles (A, arrows) and scalloping of the posterior
aspect of several vertebrae (B).
Conus and lumbar enlargement of the cord are almost
uniformly affected; however, abnormal signal may
extend into upper thoracic cord levels – Non specific.
Hallmark of diagnosis is demonstration of dilated pial
veins of cord, most commonly along dorsal surface.
MR reflect pathophysiologic features of SDAVF
including cord edema and venous hypertension with
engorgement of the pial veins
Ischemia and venous infarct can occur.
SPINAL ANGIOGRAPHY :
•AVF shunt below or medial to the pedicle .
•The draining vein is almost 10 times larger than feeding
•The arterial flow is slow .
•Recently, the use of time-resolved imaging of contrast
kinetics (TRICKS) has improved the detection rate and
accuracy of MRA and DSA for diagnosis and localisation
is often unnecessary.
Type II (Glomus AVMs)
Analogous to intracranial AVMs
Tightly packed nidus of dysmorphic
arteries and veins in direct
communication w/o capillary bed; over a
short segment of the spinal cord
The nidus may be completely or partially
Typically lie in the anterior half of the
spinal cord and are supplied by one or
two medullary arteries via the anterior
Usually at the cervicothoracic junction
• Multiple branches of ASA
•Relatively low resistance
•High blood flow
Pathophysiology of Type II
Vascular steal mechanism: High-flow lesion; AVM
nidus acts as a low-resistance sump siphoning blood
away from the surrounding normal spinal cord
Dysmorphic vessels susceptible to hemorrhage
Mass effect: myelopathy or radiculopathy
Clinical Presentation of Type II
Childhood or adult years
Acute presentation from subarachnoid or intramedullary
hemorrhage is most common
Acute onset of severe neck or back pain “coup de
poignard” approximates the level of AVM: typically the
first symptom of AVM hemorrhage
Vascular anatomy – Intradural AVMs
Juvenile type (TYPE 3):
These lesions are fed by multiple
enlarged medullary arteries via the
anterior and posterolateral spinal
arteries and may have a
voluminous nidus that completely
fills up the thecal sac.
The nidus also has intervening
These may frequently involve
vertebrae and paraspinal tissues .
These lesions are high-flow AVMs;
a spinal bruit may indicate their
• MALE or FEMALE
• Age : 2 or 3 decade
Nearly 50 % < 16 years .
• 30 % weakness as initial symptoms
• 20 % Back pain at onset .
• Over 70 % develop sensory symptoms
• 50 % Spinal hemorrhage
• Bladder & bowel involvement
•Slow flow AVM Myelopathic symptoms .
• High flow AVM Bleed:
•SAH OR intramedullary bleed ,
•High mortality ( 30 % )
•High rate of bleeding (40 % within first year )
ACUTE MEDULLARY SYNDROME .
May progress rapidly , or there may be partial
Prognosis : Poor .
Flow voids representing enlarged arterial feeding vessels
and intramedullary nidus are well seen
Haemorrhage is also seen in various stages.
Nonhemorrhagic intramedullary signal abnormality
adjacent to the nidus and most likely indicates gliosis,
edema, or areas of cord infarction.
Extension of nidus into extramedullary structures,
paraspinal soft tissue structures, is also well seen on MR
Angiographic evaluation of delineation of all feeding
vessels, aneurysms, locating the nidus within the cord,
and mapping the size and location of draining veins.
intramedullary (AVM) of
the cervical and thoracic
anteroposterior (A) and
lateral (B) views,
superior aspect of a large
intramedullary AVM that
extends from C4 to T2.
The nidus of the AVM fills
the spinal canal from
front to back and from
side to side.
On sagittal T1-weighted
magnetic resonance imaging ,
the signal void from the AVM
clearly involves not only the
cross-sectional area of the spinal
cord but also the anterior and
posterior elements of the spine
and paraspinous soft tissue
Selective spinal cord arteriogram demonstrating a
glomus-type intramedullary arteriovenous
malformation supplied by the anterior spinal
artery via the artery of Adamkiewicz
Feature SDAVF SCAVM
Age >4th decade 2nd-3rd decade
Symptom onset Slow progressive Acute
Male predominance Yes (marked) Minimal
Hemorrhage No Yes (frequent)
Bruit No 5-10%
Origin Acquired Congenital
Site of nidus Dura, root sleeve Spinal cord
Perimedullary arteriovenous fistulas
Consist of direct AVF located on
the cord and fed directly by arteries
supplying the cord, most frequently
8-19 % of spinal AVM.
Single hole between one or more
radiculomedullary arteries &
perimedullary veins on the surface
of cord .
Features that differentiate SCAVFs
from both SDAVFs and SCAVMs
Intradural location of shunt,
constant involvement of arteries supplying
the spinal cord, and
lack of intervening nidus
Etiology And Clinical Presentation
Believed to be congenital lesions, usually present in patients in
their second through fourth decade
Most common neurologic presentation is one of progressive
asymmetrical radiculomedullary signs involving lower
extremities, reflecting the most common location of SCAVFs in
the lower thoracic or lumbar region
Hemorrhage is also common and has been noted in nearly one
third of patients at presentation
Three subtypes have been identified based on the size and
number of vessels involved
A – Simple perimedullary fistula fed by single arterial
branch. (Venous drainage minimally dilated)
B – Intermediate sized fistula with multiple dilated
arterial feeders. (ASA & PSA are mildly dilated and
draining vein markedly dilated)
C – Large perimedullary fistula with multiple giant
arterial feeders.(Main supply is ASA and draining
proximal venous segment is ectatic)
Young adults , 2 – 4 Decade
No sex predilection .
Most common presentation :
• Progressive asymmetrical radiculomedullary signs,
involving lower extremities .
• Progressive paraplegia without remission.
• Impaired venous return & long intradural course of
the venous drainage may be responsible for
ascending myelopathy & spinal cord ischaemia .
• Spinal SAH In 1/3 patients .
Flow voids - enlarged feeding and draining vessels of
Intrinsic cord signal abnormality and evidence of
hemorrhage may also be present.
Small size of some lesions and lack of nidus may make
differentiation from SDAVF difficult.
Abnormal enhancement of the cord may be present.
Radiological differences between dural
AVM and Intradural Avm
Dural AVM Intradural AVM
Site of nidus Lateral canal
Within cord 80%
Level of spine Lower half diffuse
Rapid flow 0 80%
Assoc aneurysm 0 44%
Route of drainage Rostral 100%
(CMs) are slow flow vascular
malformations without AV
3% to 5% of CMs involve the
Site- Most often intramedullary
and occur proportionally
throughout the cord
CMs of the spine have been
noted to preferentially affect
It can arise denovo, post
radiotherapy and post traumatic.
Symptoms may begin at any age, patients most often
present in the fourth decade
Acute presentation is probably secondary to hemorrhage
either within vascular spaces of malformation or into
surrounding parenchyma (hematomyelia)
Progressive myelopathy may result from growth or
enlargement of the lesions by several mechanisms
including vessel dilation, repeated hemorrhage, or
Varies in size from mm to cms.
Well demarcated with low grade hemorrhage of
Surrounded by hemosiderin stained gliotic neural
Histology show single cell layer to hyalinized,
thickened walls containing densely packed
collagen but no elastic or smooth muscle fibres.
Cavernous Malformation- treatment
They are not subjects for endovascular treatment, and
surgical resection is advocated for symptomatic lesions.
It is generally reserved for symptomatic lesions
Treatment planning for spinal vascular
arteriovenous lesions is based on
The hemodynamics of the lesion,
Location in the axial and longitudinal plane, and
Poly vinyl alcohol(150-250micro) :Temporary & Reduces arterial steal
N-butyl cyanoacrylate (NBCA) : If AVM is supplied by only PSA
ethylene vinyl alcohol copolymer)
If AVM is supplied by ASA , embolization only if :
Normal anterior RMA supplying above & below the
Superselective catheterization , close to nidus.
Treatment - Dural AVF
Goal of treatment of spinal dural AVF is permanent
elimination of of venous congestion of the spinal
Simple interruption of the AvF produces permanent
resolution of venous congestion and improvement
Medullary vein(arterialised) is coagulated
Neurological outcome is closely related to preop
Endovascular occlusion of SDAVF is possible in
more than 80% of cases and can be accomplished
at the same time as the diagnostic angiogram using
permanent liquid embolic agents such as
NBCA(N-butyl cyanoacrylate) or ONYX.
Perimedullary venous thrombosis.
Clinical symptoms may worsen.
Post procedure anticoagulation for 3 months.
Treatment - Dural AVF
TREATMENT : AVMs
Should be pursued aggressively because of the poor
outcomes in untreated patients.
AIM : To suppress the risk of hemorrhage & arrest
progression of neurological defecit .
Maximum suppression of arterial steal may reverse a
progressive neurological defecit.
• Method of choice .
• Risk of embolization is 3 to 5 times lower
than surgery .
• Angiographic criteria for endovascular
Enlarged prominent ASA
Multiple commissural branches
participating in AVM .
Normal ASA above or below the AVM .
TREATMENT : Perimedullary AVF
Type I: Embolisation is not indicated if the fistula is surgically accessible since
surgery is the safer and more reliable treatment.
• Catheterisation in the anterior spinal artery can be difficult and is always
• Fistulas situated on the ventral cord surface are candidates for embolisation
which has been performed with particles (as a presurgical manoeuvre) or
Type II: If the fistula is situated on the dorsal surface of the cord, surgical ligation
and embolisation are of equal value and efficacy.
• Ventral lesions are difficult cult to approach surgically but difficult cult to
completely exclude by embolisation, if there are multiple feeders
Type III: The high-flow and dilated vessels in this type makes surgery difficult, and
embolisation with coils or liquids is usually performed as curative or presurgery
TREATMENT : Perimedullary AVF
1. Smaller lesion ,
2. AVF I & II , located posterior to the spinal cord
3. Endovascular treatment failed in AVF III .
Intradural arteriovenous fistula at surgery (A) Before, (B) After
Summary of outcomes of treatments for spinal
Intramedullary AVM Surgery Curative resection
Embolisation (curative or
Particles: high recurrence
NBCA: better cure rates
Onyx: no data
Perimedullary AVF Type I. Surgery (or embolisation)
treatment if AVF accessible
NBCA embolisation, but
particles may be safer
Perimedullary AVF Type II EVT (or surgery) NBCA, particles or surgery
Perimedullary AVF Type
EVT (surgery if
Coils, (balloons), NBCA or
DAVF EVT (surgery if recurrent) NBCA or Onyx
Indications for occluding only the feeding vessels
Intramedullary diffuse AVM
Conus medullaris AVM
Complications that result from open surgical ligation or
Infection of meninges (meningitis)
Cerebrospinal fluid leak
Complications that result from the endovascular technique
Pseudoaneurysms and thrombosis
Single high dose SRS
20 to 30% rate of occlusion.
Internal fiducial markers and image‐guided
radiation allow stereotactic irradiation for spinal
disease with real‐time verification and an
accuracy of ±1 mm for every 0.03 seconds
Minimal Acute or
1 Leg weakness, abnormal gait or stance, but no restriction of activity
2 Restricted activity
3 Requiring 1 stick for walking
4 Requiring 2 sticks, crutches, or walker
5 Confined to wheelchair
Grade Micturi tion
1 Hesitancy, frequency, urgency
2 Occasional urinary incontinence or retention
3 Total incontinence or persistent retention
Modified Aminoff-Logue grading scale