SPINAL AVM – CLASSIFICATION AND MANAGEMENT

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Spinal Cord Vascular Malformations

It represent a heterogeneous group of non-neoplastic vascular

abnormalities

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.

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Incidence

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

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HISTORY AND CLASSIFICATION

Classification of spinal AVM has evolved with thetechnology available to study them.

Earliest studies were based on postmortem examinations.

1888, Gaupp described them as “hemorrhoids of the piamater spinalis”.`

In 1914, Charles Elsberg performed the first successfuloperation on a spinal cord AVM.

1925 – Sargent: classified 19/21 cases as venous angiomas

1943 – Wyburn Mason classified AVMs into histologicalgroups arteriovenous angiomas and purely venousangiomas(more common)

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Baker –layton in 1967 classified AVM s into 3

categories:

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

AVMs.

HISTORY AND CLASSIFICATION

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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

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Classification: Berenstein A(1999)

Spinal cord vascular malformation

Isolated - AVMs and Av fistulas

Multiple – Metameric (Cobb syndrome and otherassociations) and non metameric (Rendu –Osler– weber syndrome)

• Spinal cord telangiectasias

• Cavernomas

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Classification: Anson, Spetzler(1992)

Most widely accepted. 4 types

Type 1: AV Fistula located between a duralbranch of the spinal ramus of a radicular arteryand an intradural medullary vein

Type 2 : Intramedullary glomus malformationwith a compact nidus within the substance of thespinal cord

Type 3: Juvenile or combined AVMs -extensiveAVM often extending to the vertebra orparaspinal tissues.

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Type 4 : Intradural perimedullary arteriovenous

fistula

A – simple fistula fed by a single arterial

branch.

B – Intermediate sized fistula with multiple

dilated arterial feeders

C – Large perimedullary fistula with multiple

giant arterial feeders.

Classification: Anson, Spetzler(1992)

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MODIFIED CLASSIFICATION OF

SPINAL CORD VASCULAR LESIONS

1. NEOPLASTIC VASCULAR LESION

• Hemangioblastoma

• Cavernous malformation

2. SPINAL ANEURYSM

3. AVF :

Extradural

Intradural

• Ventral (Small/Medium/Large shunt)

• Dorsal (Single/Multiple feeder)

4 AVM

• EXTRADURAL-INTRADURAL

• INTRADURAL

• CONUS MEDULLARIS

Spetzler and Detwiler 06-Jan-1610

Arterial Anatomy

1. Anterior spinal artery: Arises from the fusion of a contribution from each of the vertebral

arteries

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

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Arterial Anatomy

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

Medullary branch: 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 Adamkiewicz

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Arterial Anatomy

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Venous Anatomy

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 cranial dura

It drains into the ascending lumbar veins and the azygousvenous system

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Pathophysiology of Symptoms

Depends on the type of the AVM

High-flow:

Ischemia

Hemorrhage

Slow-flow:

Venous congestion

Mechanical compression of the spinal cord and

roots

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CLINICAL PRESENTATION

The clinical signs are due to:

(1) SAH;

(2) haematomyelia;

(3) steal into AVF/AVM;

(4) venous hypertension;

(5) thrombosis of draining vein,

(6) pressure of aneurysm, venous or arterial, true or false;

(7) arachnoiditis;

(8) syringomyelia and

(9) Foix-Alajouanine syndrome, a result of chronic venousischaemia of the spinal cord.

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Dural Arterio-

Venous Fistula

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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

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Dural AV Fistula

Medullaryvein

Spinal Dural Arteriovenous Fistula

Represent at least 35% of all spinal vascularmalformations in large series, although some estimatesrange as high as 80%

Most commonly occur at thoracolumbar levels, usuallybetween T5 and L3

It represents an AV shunt that occurs within duralcovering of spinal cord, below and medial to the pedicle.

Located adjacent to intervertebral foramen or withindural root sleeve, with arterial supply arising from duralbranch of radicular artery.

An intradural vein drains the shunt directly into the pialveins of the cord

J Neurosurg 1983;59:1019-1030.06-Jan-16

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Pathophysiology

AV shunting result in venous engorgement andvenous hypertension involving the spinal cord(Venous congestion, steal phenomenon, ischemiaand hemorrhage)

Most often, no direct arterial supply to the spinalcord itself originates from the radicular arteryfeeding an SDAVF.

In 10% to 15% of cases, however, SDAVF is fedby a radicular artery that also supplies spinal cordvia a radiculomedullary or radiculopial branch

Radiology 1985;154:687-689.06-Jan-16

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SUBACUTE NECROTIZING MYELOPATHY

VENOUS HYPERTENSIVE MYELOPATHY &

Cord edema, stagnation of bloood flow , blood – CNS disruption

Intramedullary vasodialation, Loss of autoregulatory capacity

Tissue perfusion ( hypoxia )

Intramedullary arteriovenous pressure gradient

Venous engorgement & venous hypertension

Increased pressure & engorgement of pial veins

Intradural vein Pial veins

PATHOPHYSIOLOGY

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Clinical presentation

Most common spinal vascular anomaly in older adult, afflicts malesin 80% to 90% of cases

Presents after the fourth or fifth decade;

Chronic progressive myelopathy leads to progressive lower extremityweakness, 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

heavy meal

Lead to paraplegia within 2 – 4 years.

Never bleeds.

15% of the patients have rapid neurological worsening and is called

Foix alajouanine syndrome and is due to venous congestion andshould be treated immediately 06-Jan-16

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Imaging

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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).

MRI

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 pialveins 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.

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SPINAL ANGIOGRAPHY :

•AVF shunt below or medial to the pedicle .

•The draining vein is almost 10 times larger than feeding

artery.

•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.

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Type II (Glomus AVMs)

Analogous to intracranial AVMs

Tightly packed nidus of dysmorphicarteries and veins in direct communication w/o capillary bed; over a short segment of the spinal cord

The nidus may be completely or partially intramedullary

Typically lie in the anterior half of the spinal cord and are supplied by one or two medullary arteries via the anterior spinal artery

Usually at the cervicothoracic junction

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glomus type

•Compact nidus

•Intramedullary

• Multiple branches of ASA

& PSA

•High pressure

•Relatively low resistance

•High blood flow

•Aneurysm common 06-Jan-1629

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

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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

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Juvenile

Spinal

AVM

Intramedullary

& extramedullary

+/-

extraspinal

extension

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Vascular anatomy – Intradural AVMs

Juvenile type (TYPE 3):

These lesions are fed by multipleenlarged medullary arteries via theanterior and posterolateral spinalarteries and may have avoluminous nidus that completelyfills up the thecal sac.

The nidus also has interveningneural tissue.

These may frequently involvevertebrae and paraspinal tissues .

These lesions are high-flow AVMs;a spinal bruit may indicate theirpresence.

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JUVENILE SCAVM

EXTRADURAL-INTRADURAL AVM

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SYMPTOMS

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• 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:

•HEMORRHAGE :

•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

remissions.

Prognosis : Poor .

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Imaging

Flow voids representing enlarged arterial feeding vesselsand intramedullary nidus are well seen

Haemorrhage is also seen in various stages.

Nonhemorrhagic intramedullary signal abnormalityadjacent 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 feedingvessels, aneurysms, locating the nidus within the cord,and mapping the size and location of draining veins.

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IMAGING : AVMs

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MRI : best noninvasive modility

Flow voids enlarged arterial feeding vessels

Intramedullary nidus

Recent / remote intramedullary hemorraghe

T2W Hyperintensity : gliosis, edema, infarction

Draining veins :

• Flow voids,

• Ectasia ,

• Mass effect,

• Thrombosis

Intramedullary contrast enhancement

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Juvenile-type intramedullary (AVM) of the cervical and thoracic segments Right vertebral arteriography,anteroposterior (A) and lateral (B) views,demonstrates the 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.

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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

glomus type

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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

Medullary arterial supply involved

10-15% 100%

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Perimedullary

Fistula

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Perimedullary arteriovenous fistulas

Consist of direct AVF located on the cord and fed directly by arteries supplying the cord, most frequently the ASA

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

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AV fistula

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

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Perimedullary AVF

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)

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SYMPTOMS

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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 ofthe venous drainage may be responsible forascending myelopathy & spinal cord ischaemia .

• Spinal SAH In 1/3 patients .

IMAGING

Flow voids - enlarged feeding and draining vessels of

SCAVF.

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.

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PERIMEDULLARY

AVF

3D PC MRAT1WI

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MRISCAVM PMF SDAVF

Flow voids + + +

Parenchymal signal changes

+ + +

Aneurysm + + -

Hemorrhage + + -

Nidus in the cord - -

06-Jan-1650

Radiological differences between duralAVM and Intradural Avm

Dural AVM Intradural AVM

Site of nidus Lateral canal

100%

Within cord 80%

Level of spine Lower half diffuse

Rapid flow 0 80%

Assoc aneurysm 0 44%

Supply by

medullary artery

15% 100%

Route of drainage Rostral 100%

Caudal 4%

Rostral 81%

Caudal 72%

06-Jan-1651

Cavernous Malformation

Cavernous malformations(CMs) are slow flow vascularmalformations without AVshunting

3% to 5% of CMs involve thespine

Site- Most often intramedullaryand occur proportionallythroughout the cord

CMs of the spine have beennoted to preferentially affectfemales

It can arise denovo, postradiotherapy and post traumatic.

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Clinical presentation

Symptoms may begin at any age, patients most oftenpresent in the fourth decade

Acute presentation is probably secondary to hemorrhageeither within vascular spaces of malformation or intosurrounding parenchyma (hematomyelia)

Progressive myelopathy may result from growth orenlargement of the lesions by several mechanismsincluding vessel dilation, repeated hemorrhage, orcapillary proliferation

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IMAGING

Varies in size from mm to cms.

Well demarcated with low grade hemorrhage of

varying ages

Surrounded by hemosiderin stained gliotic neural

tissue.

Histology show single cell layer to hyalinized,

thickened walls containing densely packed

collagen but no elastic or smooth muscle fibres.

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Cavernous Malformation- treatment

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They are not subjects for endovascular treatment, and

surgical resection is advocated for symptomatic lesions.

It is generally reserved for symptomatic lesions

AVM/AVF-Treatment

Treatment planning for spinal vascular

arteriovenous lesions is based on

The hemodynamics of the lesion,

Location in the axial and longitudinal plane, and

The angioarchitecture.

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EMBOLIC AGENTS

Particulate materials Poly vinyl alcohol(150-250micro) :Temporary & Reduces arterial steal

safely.

Gelfoam

Sponge microparticulate

Balloon occlusion

Liquid agents 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

AVM. Superselective catheterization , close to nidus.

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Treatment - Dural AVF

Goal of treatment of spinal dural AVF is permanentelimination of of venous congestion of the spinalcord

Simple interruption of the AvF produces permanentresolution of venous congestion and improvementof myelopathy.

Medullary vein(arterialised) is coagulated

Neurological outcome is closely related to preopfunction.

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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

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TREATMENT : AVMs

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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.

EMBOLIZATION

• Method of choice .

• Risk of embolization is 3 to 5 times lower

than surgery .

• Angiographic criteria for endovascular

approach is

Enlarged prominent ASA

Multiple commissural branches

participating in AVM .

Normal ASA above or below the AVM .06-Jan-16

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TREATMENT : Perimedullary AVF

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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

hazardous.

• Fistulas situated on the ventral cord surface are candidates for embolisation

which has been performed with particles (as a presurgical manoeuvre) or

NBCA

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

procedures.

TREATMENT : Perimedullary AVF

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SURGERY :

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

obliteration

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Summary of outcomes of treatments for spinal

vascular malformations

06-Jan-16

Intramedullary AVM Surgery Curative resection

if possible

Embolisation (curative or

palliative)

Particles: high recurrence

NBCA: better cure rates

Onyx: no data

Perimedullary AVF Type I. Surgery (or embolisation)

Surgery first-line

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

III

EVT (surgery if

incomplete)

Coils, (balloons), NBCA or

Onyx

DAVF EVT (surgery if recurrent) NBCA or Onyx

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Indications for occluding only the feeding vessels

Dural AVM

Intramedullary diffuse AVM

Combined AVM

Conus medullaris AVM

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Complications

Complications that result from open surgical ligation orresection

Infection of meninges (meningitis)

Cerebrospinal fluid leak

Wound dehiscence

Complications that result from the endovascular technique

Femoral hematoma

Pseudoaneurysms and thrombosis

Arterial dissection

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Stereotactic radiosurgery

Single high dose SRS

20 to 30% rate of occlusion.

Hypofractionated irradiation

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

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Type Typical

location

Vascular

supply

Presentation &

course

Clinical

associations

Treatment

DAVF Lumbar,

thoracic

Dural

arteries

Chronic

myelopathy

None 1.Embolizati

or

2.Surgery

AVM Cervical,

thoracic,

Lumbar

Spinal

arteries

(ASA,

PSA)

Acute;

hemorrhage

common

Vascular

syndromes;

paraspinal

involvement

rarely

1.Embolizati

or

2.Surgery

PAVF Lumbar,

thoracic

Spinal

arteries

(ASA >

PSA)

Acute or

chronic; may

hemorrhage

None 1.Embolizati

or

2.Surgery

CM Cervical,

thoracic,

Lumbar

Minimal Acute or

chronic; may

hemorrhage

Intracranial or

familial CM

Surgery

06-Jan-1669

Grade Gait

0 Normal

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

0 Normal

1 Hesitancy, frequency, urgency

2 Occasional urinary incontinence or retention

3 Total incontinence or persistent retention

Modified Aminoff-Logue grading scale

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THANK YOU

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