Radiological notes on cerebral arteriovenous malformation

1. Cerebral AVM

2. Cerebral AVM
Brain AVMs are congenital high flow
vascular malformation consisting of
an abnormal tangle of small vessels
(nidus) which directly connect brain
arteries to brain veins, without any
capillaries in-between.
85% are supratentorial

6. Clinical presentation
 hemorrhage 65%
 ischemic events due to vascular steal from
normal brain.
 Seizures 20%
 headaches
 incidental finding in asymptomatic patients
15%

7. Diagnosis
7
With increased availability of MRI and CT scans,
many patients are found to have an AMV after
having a scan for an unrelated problem. Following
AVM diagnosis, patients are usually referred to
neurointerventional radiologist and/or
neurosurgeon, and undergo a diagnostic cerebral
angiogram.

8. Radiological diagnosis
The imaging features of a brain AVM are
(a) the presence of a nidus embedded within the brain
parenchyma, identified at either cross-sectional imaging (CT,MR)
or conventional angiography.
(b) early venous drainage, which is best seen on dynamic studies,
the standard of reference being conventional catheter
angiography.

9. Radiological diagnosis
 The nidus containing numerous serpentine vessels that appear
hyperdense in CT and flow void on MRI, there are usually
changes in the adjacent brain including gliosis, dystrophic
calcification, and blood products.
 AVM replaces rather than displaces brain, it causes minimal
mass effect.

10. Imaging findings
10
If a nidus is present, two subtypes of abnormal networks of vessels can be
encountered.
The typical type is the glomerular or compact type nidus, which consists of
abnormal vessels without any interspersed normal brain tissue .
The more rarely seen second type is the so-called diffuse or proliferative type
nidus, in which normal brain parenchyma is interspersed throughout the
tangle of vessels.
If this finding is present, proliferative angiopathy or cerebrofacial
arteriovenous metameric syndrome (CAMS) must be included in the
differential diagnosis and can be distinguished from a true brain AVM on the
basis of the absence of early venous drainage seen in proliferative angiopathy
and the classic location and association with facial AVMs seen in CAMS.

11. Imaging findings
11
Many vascular lesions can manifest with abnormal vessels in the brain
at imaging and must be differentiated from one another due to their
different natural histories and the various treatment strategies. For
example, classic brain AVMs and pial arteriovenous fistulas (AVFs)
should be managed according to the risk associated with the disease
versus treatment-related risk, DVAs are normal variants that never
require treatment.

12. Imaging of Brain AVMs:
What the Clinician Needs to Know
 Previous hemorrhage.
 Intranidal aneurysm.
 Venous stenosis.
 Deep venous drainage.
 Single venous drainage.
 Deep or posterior fossa location.
Risk of future hemorrhage:

19. 19
The most important clue to the diagnosis of CAMS is the
presence of multiple AVMs in both the brain parenchyma and
the facial region. The brain AVMs have a characteristic
distribution, consisting of diffuse or proliferative type nidus
with supply from multiple small perforator collateral vessels
with rather slow arteriovenous shunting into the veins, which
makes these AVMs extremely difficult to treat.
Cerebrofacial Arteriovenous
Metameric Syndrome

20. Cerebrofacial Arteriovenous Metameric
Syndrome

21. 21
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.
The lack of clear early venous drainage on dynamic images is
the key to differentiating this disease from classic brain AVM.
Proliferative angiopathy

22. Proliferative angiopathy

23. 23
Developmental Venous Anomalies
Although they are not classified as
AVMs, DVAs may manifest at cross-
sectional imaging with an
intraparenchymal tangle of vessels
and represent extreme variants of
the normal transcerebral venous
system.

24. Apart from conservative management, there are three treatment options for
brain AVMs: surgery, endovascular embolization, or radiosurgery.
Surgery can provide a rapid cure in suitable cases (smaller and cortical-
based brain AVMs)
Endovascular embolization is another treatment option that can be used to
quickly eliminate angiographic risk factors. however, the cure rate with
embolization alone is relatively low .
Radiosurgery has a high cure rate with relatively low complication rates.
However, its major limitation is that radiation is slow to take effect; it may be
up to 2 years before any shrinkage of the brain AVM is seen.
Conservative management is typically used when the risk posed by treatment
is too high, such as in large brain AVMs or in asymptomatic patients who are
believed to have a low risk of future hemorrhage.
TREATMENT

25. The Spetzler-Martin (AVM) grading
system
size of nidus
small (<3 cm) = 1
medium (3-6 cm) = 2
large (>6 cm) = 3
venous drainage
superficial veins only = 0
deep veins = 1
eloquence of adjacent brain
non-eloquent = 0
eloquent = 1
eloquent brain
sensorimotor, language, visual cortex, hypothalamus, thalamus, brain
stem, cerebellar nuclei, or regions immediately adjacent to these
structures
non-eloquent brain
frontal lobe, temporal lobe, cerebellar hemispheres

26. Embolization

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