Dural Arteriovenous MalformationsMohamad Kanso

MED IV

Neurosurgery applicant

Outline

Overview of AVMs

DAVMS

Intracranial

Epidemiology

Etiology

Common locations

Classification

Natural History and Prognostication Factors

Evaluation

Management

Spinal DAVMs

Conclusion

Arteriovenous malformation (AVM) Dilated arteries and veins with dysplastic vessels.

Grossly “tangle” of vessels,

circumscribed center (Nidus)

Arterialized veins (Red)

Arterial blood flows directly between them with no capillary bed & no intervening neural parenchyma in nidus

In adulthood, AVMs are medium-to-high pressure and high-flow

AVMs are:

• Usually presents with hemorrhage, less often with seizures

• Not congenital, but acquired.

• Risk of bleeding: ≈ 2-4% per year

• Demonstrable on angiography, MRI, or CT (especially with contrast)

• Main treatment options: stereotactic radiosurgery, endovascular approach, or surgical excision

May be classified as:

1. Parenchymal AVMs

Subclassified as:

- Pial

- Subcortical

- Paraventricular

- Combined

2. Pure dural AVM

3. mixed parenchymal and dural (rare)

DAVMs- History Rizzoli was the first to describe an arteriovenous malformation (AVM) that

involved the dura mater

Rizzoli (1873) Observed a right Occipital pulsating swelling in a 9-year-old girl.

The pulsation disappeared on compression Of the left occipital artery.

The girl died from an apparent meningitis (perhaps, in fact, from an intracranial hemorrhage).

At autopsy she was found to have an AVM of the occipital region (-duralpial) with drainage to the transverse sinus.

There was a defect in the occipital region Of the skull so that the pulsation in the AVM could be felt externally.

Sachs reported the first, angiographic description in 1931.

In the 1970s , it was realised that venous drainage influenced DAVM’s behaviour, notably by Aminoff and Kendall

Dural AVMs

• Not true AVMs in the usual sense; qualify more as direct fistulas

Direct fistula AKA arteriovenous fistula.

Single or multiple dilated arterioles that connect directly to a vein without a nidus.

These are high-flow, high-pressure.

• May develop by

• opening of existing microshunts within the dura

• angiogenesis leading to the development of new shunts.

DAVMs

Intracranial Spinal

Intracranial Dural AVMs

• Rare

• Vascular abnormality in which an arteriovenous shunt is contained within the leaflets of the dura mater

• Supplied by branches of the carotid or vertebral arteries before they penetrate the dura.

• May be multiple.

Cerebral angiogram of a cerebral dural arteriovenous malformation. The nidus is located at the cerebral convexity (arrow). There is rapid filing of the cerebral venous system after injection of contrast into one internal carotid artery.

EPIDEMIOLOGY

DAVMs comprise 10-15% of all intracranial AVMs

Modest male predominance (higher-grade lesions)

Age: 40-50 year

Rare in Pediatric age group Complex

bilateral.

Common locations:

DAVMs may occur anywhere within the cranium or the spinal canal.

Usually within the wall or immediately around the venous sinuses:

1.Transverse sinus: the most common with a slight left-sided predominance

2.Posterior cavernous sinus: Usually drains to junction of transverse and sigmoid sinuses

Cavernous Sinus 15 %

Transverse Sinus 55% (Most Common)

Tentorium 10%

Anterior Fossa 6 %

Others 14%

Most Common locations:

ETIOLOGY

The etiology and pathogenesis of the DAVM is still not fully understood.

Acquired lesions (Not congenital)

Associated with stenosis or occlusion of the draining dural sinuses.

The evidence for DAVMs being

Acquired is more compelling

*Lucas CP, Zabramski JM, Spetzler RF, Jacobowitz R. Treatment for intracranial dural arteriovenous malformations:a meta-analysis from the English language literature. Neurosurgery. 1997

has been proposed as the most probable pathogenic mechanism

ETIOLOGY

Venous Thrombosis

Controversy exists

Cause

Prothrombin gene mutation sinus

thrombosis DAVM(Singh et al. 2001)

Result

A normal sinus prior having a DAVM was documented in several papers (Convers 1986)

OR?

Is venous thrombosis a cause or a result for DAVM?

Result

Trauma: A Possible Etiology..

TraumaRupture arteries

adjacent to veins

Fistula OR

Transient Sinus Thrombosis

Stimulate VEGF

Angiogenesis

Head injuryS

inus compression by a Tumor

Changes in AV pressure gradientsOpens AV microshunts between

dural vessels

DAVM

Other Possible Etiologies

Pathomorphology of dural arteriovenous malformations

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

Primary and secondary arteriovenous shunts are seen on the venous side of the network.

Left Sigmoid SinusLeft occipital artery injection () (AP) viewDrained by the ipsilateral jugular vein (broken )

Macroscopic image of the same DAVM taken during autopsy. The sigmoid is opened ().

Spongy, fibrous material (broken arrow) fills the lumen of the involved segment of the sinus.

Microscopic section of the spongy tissue removed from the sinus

Multiple cross sections of thin-walled sinusoidal vascular structures () within fibrous proliferating tissue

Classification

There are several classification systems in use.

The more recent and most commonly used classification scheme are those developed by Borden et al. and Cognard et al.

Classification is mainly based on venous drainage

DAVMs draining into a cortical vein classified as dangerous

The Cognard et al. classification is based on angiographic patterns.

Borden

Based on:• site of venous drainage• Presence of CVR• Nb of Fistula

Advantage: simple without loss of predictability

Cognard

Based on:• Direction of venous drainage• Presence or absence of CVR• Venous outflow architecture

(ectasia)

Advantage: Permits an accurate comparison of clinical and radiological parameters

Classification

(1995)

Cognard (Types I and IIa)

Type I and IIa: 54% of DAVMs

Exhibit benign behavior.

Low Risk DAVM

(I or IIa)

Persistance of Arterial blood

flow in dural sinus

Mechanical obstructio

n of the sinus

Retrograde drainage of

blood away into the cortical vein

Transforming into High risk lesion

2-4% chance that a low risk lesion can transform into a High risk lesion

As a general rule: lesions with retrograde flow in the cortical veins (IIb, III & IV ) are high risk (for bleeding or intracranial hypertension).

Clinical presentation:

Considered as an additional independent factor determining the clinical course of these lesions.

Lesion with benign presentation Better clinical course (than those with an aggressive)

Benign Presentation Aggressive Presentation

Bruit Spontaneous haemorrhage

Headache Focal neurological deficits

Seizures

Clinical presentation: highly variable

Often symptoms depend on the location and the anatomy of the lesion.

Intracranial Hemorrhage

Non-hemorrhagic neurologic manifestations

Presentation

Pulsatile tinnitus

Focal neurologic deficits

Reversible Parkinsonis

mSeizures

Progressive dementia (venous

hypertensive encephalopathy

)

Hydrocephalus

CHF (Neonate

s)

18% of DAVFs presented with

hemorrhage. Congard et al.

Often symptoms depend on the location and the anatomy of the lesion.

Natural History and Prognostication Factors Annual risk of hemorrhage in an unruptured DAVM is 1.5-1.8%

Patients with hemorrhage experienced excess mortality until 7 years after admission

The presence of intracranial venous hypertension in intermediate and high grade lesions is the ultimate determinant of poor long term prognosis,

Risk of Hemorrhage depends on

venous drainage pattern

(cortical venous reflux)

presence or absence of aggressive symptomson clinical

presentation

Natural History and Prognostication Factors Lack of CVR (Cognard types I and IIa) is associated with a benign

natural history with an extremely low risk of intracranial hemorrhage.

Annual mortality rate of 10.4%,

Annual risk of intracranial hemorrhage of 8.1%

An annual risk of non-hemorrhagic neurologic deficit of 6.9%

Seizures

Parkinsonism

cerebellar symptoms

failure to thrive

Cranial nerve deficits)

Conversely the presence of CVR (Cognard type IIb-V) is an aggressive feature and is associated with a high risk of hemorrhage:

Can demonstrate:• Dilated

vessels • Venous

Pouches • Vascular

Enhancement • Signs of

Venous Hypertention

Limited to Rule out:• Intracranial

Hemorrhage

• Edema due to Venous Congestion

Permits an assessment of DAVM:

• Anatomically• Hemodynamical

ly• With crucial

relevance for planning therapy.

Non-Contras

t CT

Angiography

(Gold Standard)

MRI

Raises suspicion

Initially

• MRA :• limited value in providing information about

angioarchitecture of the DAVM • Not sufficiently conclusive for decision making.

EVALUATION (Acute)

Evaluation (chronic symptomatology)

CT and MRI (with contrast)

Both demonstrating engorged cortical veins over the surface of the brain as well as evidence of venous congestion.

When small in size, the nidus is rarely localized, even with MRA, and the diagnosis of intracranial DAVS is not excluded with negative CT and MRI examinations.

If clinically suspicious, cerebral angiography will be required to demonstrate the presence or absence of a DAVM.

Cerebral angiography

Confirm the diagnosis

Identify the dural origin of the nidus

Outline its: Arterial supply

Venous drainage

Relationship to the venous drainage of the brain.

A venous ectasia or pseudoaneurysm may be demonstrated at angiography and attest to the venous cause of the ICH

MANAGEMENT

When to treat? Treatment Strategies:

Conservative management Surgery Stereotactic Radiotherapy Embolisation

Transarterial embolization

Transvenous embolisation

When to treat?

The decision to treat is based on clinical presentation, location, anticipated natural history and venous drainage.

Indications for intervention:

1. neurologic dysfunction

2. hemorrhage

3. refractory symptoms

***A change in a bruit (either worsening, or disappearance) should prompt restudy.

Therapeutic strategy

Based on the pattern of venous drainage of the lesion, since it determines the natural history of the DAVS.

Thus:

Type I lesions Conservative management intervention is only indicated if symptoms are distressing for the patient

(physiological obstruction to the drainage of the normal brain, which in turn may produce clinical symptoms)

Type II lesions, endovascular treatment is usually recommended

Type III and IV lesions, urgent surgical or endovascular treatment is indicated.

Aim of Treatment

Cure Palliate

completely closethe fi stula and the abnormal venous outle

• difficult without risking alterations of the venous drainage pattern

• usually performed trans-arterially.

I- Manual Arterial compression

Arterial compression may be useful in asymptomatic type I and type IIa DAVF.

Patient compresses the cervical carotid or occipital artery using their contralateral hand.

The procedure should start with short periods of compression, repeated several times a day.

The frequency and duration of compression increased over 3–4 weeks .

I- Manual Artery self compression Patients are advised to compress with the hand that

would be affected by ischemia if it were to occur Example:

with a left-sided DAVM, the right hand should be used to compress the left carotid artery).

That way, the hand would fall away if ischemia develops.

Compression is performed sitting or lying

Effective in inducing thrombosis of the DAVM in 20–30% of patients. (mimics the natural course)

Contraindicated in patients with atherosclerosis.

II- Endovascular embolization

Recent reports emphasize the important role of embolization as the first treatment for all but completely isolated (from endovascular access) lesions.

Prior to any endovascular treatment, comprehensive catheter angiography must be performed.

This should include 6-vessel cranial angiography (bilateral external carotid arteries, internal carotid arteries, and vertebral arteries)

The goal of aggressive treatment of a DAVM

A. Cure of the lesion

B. Conversion of a high risk fistula to a low-risk one

C. Palliation of symptoms caused by a low-risk lesion.

Endovascular Embolization

1.Trans-Arterial 2.Trans-Venous

1. Trans-arterial Embolisation

Complete closure is often difficult or impossible to achieve from the arterial side.

Embolic material injected from the feeding arteries is very likely to get wedged proximal to the shunt.

Transarterial embolization therefore rarely results in complete cure of DAVMs

Should be reserved for:

Cases in which the fistula cannot be reached via the transvenous route.

For the palliation of symptoms in case of low-risk DAVMs

Preoperative measure to facilitate surgery

Solid – i.e., polyvinyl alcohol particles(PVA), platinum coils –

Liquid embolics (NBCA or Onyx)

Tran-venous Embolisation

Multiple arteriovenous connections are difficult to obliterate via the feeding arteries.

Easily achieved by packing the lumen of the single venous channel of the lesion.

Transient pressure elevation inside the nidus might be induced.

--But--

rupture and bleeding does not occur, the nidus is surrounded by thick walls, reinforced by connective tissue proliferation within the dura.

Venous embolization requires thorough study of the venous circulation Venous Infarction can be induced if the normal venous draining

pathway of the brain is sacrificed.Visualization of the same venous structure (sinus or cortical vein) in both the early and late phases demonstrates

participation of the involved segment in normal venous flow

Some authors consider arterial embolization

followed by transvenous disconnection of the

involved dural sinus the most efficient strategy for

high grade DAVFs!

Location Management

Anterior Cranial Fossa Surgical

Cavernous Sinus ConservativeCompressionTransvenous Embolisation

Signoid-Transverse Sinuses CompressionTrans-arterial or Transvenous EmbolisationSurgery

Superior Sagittal Sinus Trans-arterial or Transvenous EmbolisationSurgeryCombined

Tentorial incisura EndovascularSurgeryCombined

Basal tentorial EndovascularSurgeryCombined

Torcular: EndovascularSurgery

Foramen Magnum Endovascular Surgery

III- Surgery

Surgery is generally reserved for lesions in the anterior fossa, tentorium and craniocervical junction

Preoperative embolization will usually facilitate surgical treatment.

Warnings of rapid blood loss that frequently occurs during surgery (including just incising the scalp) with one report of 8 units lost in 4 minutes following elevation of the bone flap!

Use of the Craniotome is discouraged, as a sinus or venous laceration could produce a fatal hemorrhage.

Contingencies for rapid administration of blood products must be made (large bore central lines).

III- Surgery.. continued

Patients were operated in either Semi-prone position

or

Supine with maximal head rotation.

Extra care is taken to place copious dural tack-up sutures to obliterate the epidural space which is abnormally vascular

III- Surgery.. continued

Surgical ligation of feeders is inappropriate therapy ( increase the risk of hemorrhage)

Skeletisation of the dura around a DAVM involves excision of the: nidus

sinus

Venous drainage

A complete resection is of paramount importance.

Recently, intraoperative angiography has been advocated as a useful tool for assessing the adequacy of surgical treatment

Post - operative care :

It is usually sufficient for patients to recuperate with bed rest for 24 h

Oral analgesics.

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.

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.

Lucas CP, Zabramski JM, Spetzler RF, Jacobowitz R.Treatment for intracranial dural arteriovenous malformations:a meta-analysis from the English language literature. Neurosurgery. 1997;40(6):1119–30; discussion1130–2.

Stereotactic radiosurgery

May be used post-embolization. Reports of treatment with stereotactic

radiosurgery claim complete occlusion rates of 44–87% without serious complications.

Its major disadvantage is the delay in response;

used for: low-risk lesions

lesions otherwise untreatable

Its use in combination with transarterial embolisation has been reported as effective after incomplete treatments

Stereotactic radiosurgery..

Radiosurgery represents an important adjunct to the treatment of DAVM.

Should be reserved for benign DAVM that have failed other treatments.

Aggressive DAVM require urgent and complete obliteration that cannot be provided by radiosurgery

Stereotactic radiosurgery..continued

Yang et al. reported cure rates of 83% after 2 years in selected patients. (Series of 40 patients.)

Pan et al reported: a complete obliteration rate of 58% of transverse/sigmoid fistulae treated with

only radiosurgery

or

with radiosurgery after surgery/embolization had failed

71% of the patients were cured of their symptoms.

Algorithm

Most common spinal vascular malformations

80% of all spinal AVMs

Majority located in thoracolumbar region.

Patients present in their 4th decade

Most spinal DAVMs generate spinal venous hypertension leading to myelopathy.

Untreated Permanent disabling neurological deficit. Symptoms commonly develop in a slow and fluctuating

manner.clinical diagnosis extremely difficult.

Proper imaging is of utmost importance to establish the diagnosis before permanent damage to the spinal cord occurs.

Yet the average time from the onset of symptoms until diagnosis was found to be 27 months in a large study of 66 patients with spinal DAVM (Gilbertson et al. 1995).

Venous drainage patterns of Spinal DAVMs

a Venous drainage by epidural veins (arrow). Type 1

b Venous drainage via epidural veins and a perimedullary vein (arrow) into the coronal venous plexus (arrowheads). Type 2

c Exclusive venous drainage by perimedullary vein (arrow) and the coronal venous plexus (arrowheads)Type 3

Meningeal branch of the radicular artery feeds the DAVM

Spinal DAVM

a Digital subtraction angiography,selective injection of an L.IV segmentalartery on the left (arrow).

Demonstrates a DAVM involving the nerve root sheath (curved arrow),draining into a perimedullary vein (open arrow)and into dilated spinal intradural veins (brokenarrow). b Sagittal T1-W MRI study demonstrates

large intradural vessels within the L.I–IV segments(broken arrow), typical of spinal DAVM.

INVESTIGATION

As localization of the lesion by clinical signs is often difficult or impossible

Spinal catheter angiography is highly invasive

MRI and MRA play an outstanding role as noninvasive tools in the diagnosis of spinal DAVM.

The most common signs of spinal DAVM are related to venous ischemia and include: hyperintense T2 signal (94%–100%)

enlargement (45%–65%)

gadolinium enhancement of the spinal cord (60%–88%)

Intradural serpentine structures visualized by flow void and contrast enhancement are typical direct signs of the vascular dural arteriovenous shunts

represent enlarged veins of the coronal venous plexus that drains the lesion

Management Transvenous embolization is not feasible for spinal lesions

Transarterial embolization with glue is the treatment of choice for a spinal DAVM with an arterial feeder that: allows safe and distal catheterization

does not supply the anterior spinal artery.

Glue should be pushed until it reaches the draining vein (Cognard et al. 1996; Song et al. 2001).

Clinical outcome seems to dependent on the severity of the symptoms at the time of treatment (Nagata et al. 2006).

e Microcatheter injection of the fistula prior to embolization with cyanoacrylate glue.

f Control injection of the same segmental branch following embolization demonstrates complete occlusion of the fistula.

BEFORE

AFTER

Conclusion

DAVMs are relatively rare, but should remain on your differential.

They are divided to intracranial and spinal.

There are benign lesions and aggressive ones.

They might cause a large spectrum of symptoms from tinnitus to fatal intracranial hemorrhage.

Always do a non-contrast CT for Acute patients followed by an MRI and Angiography.

Manage benign lesions conservatively; aggressive ones aggressively.

Weapons in hands:

Endovascular Embolisation

Surgery

SRS

Thank you!

Mohamad Kanso

References

1. L. Hacein-Bey et al. / Clinical Neurology and Neurosurgery 121 (2014) 64–75

Advances in Surgical Approaches to Dural Fistulas Patrick P. Youssef, MDdepartment of Neurosurgery, EmoryUniversity School of Medicine, Atlanta (2013)

M. Forsting ・ I. Wanke (Eds.)Intracranial Vascular Malformations and Aneurysms From Diagnostic Work-Up to Endovascular Therapy 2nd Revised Edition

Tutorials in Endovascular Neurosurgery and Interventional Neuroradiology. James Vincent Byrne(2012)

F. Signorelli et al. / Clinical Neurology and Neurosurgery 128 (2015) 123–129

Management of intracranial dural arteriovenous shunts in adults. Dipanka Sarma, Karelter BruggeEuropean Journal of Radiology 46 (2003) 206/220

Surgical Neuroangiography. Bernstien (2004)