Arteriovenous Malformation

KEY FACTS

TERMINOLOGY

• Pial vascular malformation of brain

○ Artery → vein shunting, no intervening capillary bed

IMAGING

• General features

○ Supratentorial (85%), posterior fossa (15%)

• CT/CTA

○ Iso-/hyperdense serpentine vessels ± Ca++

○ Arterial feeders, nidus, draining veins enhance

• MR

○ "Bag of worms"/tangle of serpiginous "honeycomb" flow

voids

○ No intervening normal brain in arteriovenous

malformation (AVM) nidus

○ Minimal/no mass effect

○ ± high signal (gliosis) on FLAIR

○ T2* GRE "blooming" if hemorrhage present

• DSA: Best delineates internal angioarchitecture, 3

components of AVM

○ Enlarged feeding arteries

○ Nidus of tightly packed vascular channels

○ Dilated draining veins

• Intranidal "aneurysm" > 50%

• Flow-related aneurysm on feeding artery (10-15%)

TOP DIFFERENTIAL DIAGNOSES

• Glioblastoma with arteriovenous shunting

• Dural arteriovenous fistula

CLINICAL ISSUES

• Annual hemorrhage risk varies widely

○ Overall annual hemorrhage risk 2-4% (cumulative)

○ However, ≤ 1% for unruptured, superficially-located nidi

with superficial venous drainage

○ ≥ 30% for ruptured, deep-seated nidi with extensive

deep venous drainage

(Left) Coronal graphic shows a

classic cerebral arteriovenous

malformation (AVM). Note the

nidus ﬉ with intranidal

aneurysm ﬊ and enlarged

feeding arteries with a

"pedicle" aneurysm ﬈. (Right)

Axial NECT (L) shows classic

serpentine hyperdensities ſt

of an unruptured AVM. CECT

(R) shows strong uniform

enhancement ﬈. Wedgeshaped configuration is

typical.

(Left) Axial T2WI shows a

classic AVM in the left parietal

lobe. The AVM nidus is seen as

a wedge-shaped mass of "flow

voids" ﬇ with its broad base

at the cortical surface. There is

no normal brain visible within

the AVM. (Right) T1 C+ FS MR

in the same case shows the

tangle of vessels within the

nidus enhances strongly ﬇.

Because AVMs are congenital

lesions and replace (rather

than displace) brain, there is

almost no mass effect present.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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