Let’s move to ones that are a little nastier
in terms of their clinical ability to cause
problems. And that’s the non-neoplastic
They’re also present at birth. They do not
go through the rapid proliferative phase of
a hemangioma. And they don’t involute.
They stay. They grow with the patient. And
about a third of them are found on the head
and neck. And they’re thought to result
when there’s an interruption at a particular
stage of development of the blood vessel so
that you don’t get to the final stage of
the blood vessel. There are in a sense primitive
And the type of malformation depends on the
stage at which this development – morphogenesis
– this development is interrupted.
And here you can see in a couple of cartoons
exactly what they look like. First of all,
you can see that the AVM actually is a direct
connection between the artery and the vein.
It bypasses the capillaries and it bypasses
the arterioles. So there’s no resistance
in there. As you remember, the resistance
is in the arterioles. So a lot of blood can
shunt through these. Often they have a number
of side vessels connected to them. There’s
a lot of blood going through that system.
This is a high-flow system. And they can actually
enlarge. And as you see in the two cartoons
on the right, you can actually see they bulge
and they can be quite irritating because they’re
not just flat and only cosmetic, like the
It’s of course, as I said, an abnormal connection
between the arteries and veins. It bypasses
the capillary system. It can appear at any
location. Most are asymptomatic but some can
cause intense pain, bleeding or can become
infected and torn. They dilate with time and
become larger. And the worst ones are, of
course, the ones in the brain where they can
A secondary type of AV malformation is the
cavernoma. And here you see instead of there
being a direct connection between the artery
and the vein, rather there’s a connection
to a whole clump of abnormal primitive blood
vessels. And in a sense, the cavernoma is
fed by both the artery and the vein. And when
these are also in the brain, they can bleed
and cause quite a lot of trouble.
The AV malformations have been classified
by two pediatric specialists in this area:
Spetzler and Martin. And they have a grading
system where you get points for a certain
number of things which I’ll talk about in
a moment. And the higher you score, the worse
is the prognosis and the more likely that
you’re going to have real clinical problems
So you can see you get various points for
the size of the AVM. The larger the AVM, the
nastier it is.
The so-called eloquence of adjacent brain,
in other words, is this in the brain area
that controls motor – arm or leg motion?
Is it in an area that controls speech? Or
is it in a silent area? If it’s in a silent
or so-called no-eloquent area, it’s much
more benign than of course if it potentially
affects speech or muscle contraction.
If the venous drainage is only very superficial,
that’s okay. But if there’s a deep component
it’s much worse because getting them out
may require sacrificing more brain tissue.
I show you this just to show you that they
can be relatively not so bad or they can be
When they’re in the brain – and here we’ll
talk a little bit about the nasty ones – they
can bleed. And the bleed most commonly presents
clinically as a subarachnoid or an intracerebral
There can be scarring following a bleed. And
that leads to seizures. There can be a mass
effect. That is if there’s enough bleeding
into it, it can actually cause the brain to
shift and this can be potentially fatal.
There can be progressive neurological deficits,
paralysis, inability to speak. And 7% of these
patients also have aneurysms that can rupture.
So this is not something that you’re happy
about when it occurs in your child.
The diagnosis is made, again, usually not
invasively although occasionally angiography
is needed. The CT scan almost always picks
that up and I’ll show you an example in
If you're not totally satisfied with the imaging
CT, MRI will give you a more detailed image.
And particularly if neurosurgical intervention
is planned, often the neurosurgeons want both
a CT angiogram to show the blood vessels feeding
it and also an MRI to show exquisitely the
anatomy. And you can also, of course, occasionally
do MRI angiography if you’re not satisfied
with the CT angiography image or if the patient
is allergic to the angiographic dye.
And finally sometimes you actually have to
put a catheter in the carotid and thread it
up into the brain and actually make a cerebral
angiogram. But these days mostly the non-invasives
And here we see an example. This is a cerebral
AVM. You can see it’s circled in green.
And then on the right-hand side, you can actually
see a CT angiogram. The tangled abnormal blood
And usually there’s an attempt to destroy
these. One way is operating and actually cutting
them out. More frequently these days, the
radiologists do it. They go up and they put
a catheter in the artery that’s feeding
one of these. And then they embolise material
that clots off these abnormal blood vessels.
And then they involute. It’s a very sophisticated
radiologic procedure. But it avoids surgery
on the brain.