Feeders Aren’t Always Friendly

Not all arteries are what they seem. In this episode, we explore a tricky group of feeders that quietly complicate your embolization plan — and why knowing their behavior changes everything.

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Script:

Okay, welcome back. Let’s dive right into arterial feeders now.

So, most of the time, arterial feeders end directly into the AVM nidus. Pretty straightforward, right?

But — and this is a big but — there’s a special group called en passage feeders.

Now… what are en passage feeders?

Basically, they’re little branches that come off a main artery that’s just traveling past the AVM. The main artery is actually heading to normal brain — not the AVM itself. But while it’s passing by, tiny side branches sneak off and start feeding the nidus.

And these feeders — they can be a real headache.

Why?

Because:

• ​ They’re hard to access with your microcatheter.
• ​ And even if you get there, embolizing them is risky.
• ​ You could end up refluxing embolic agent back into the main artery and cause brain ischemia.

And here’s the kicker — you usually don’t see these on a regular brain angiogram. Nope. You need selective angiography.

So what do we do?

We take the microcatheter we’re planning to use for embolization anyway, and we perform super selective angiograms.

But be ready: these angiograms are usually pretty diluted.

Why? Because the catheter’s tiny, and the artery’s big — so the contrast gets washed out fast by the blood flow.

Still, even if the images aren’t perfect, they give you clues.

If you want better selective images though, you can use a balloon catheter.

Here’s how it works:

You inflate the balloon to block the blood flow. Then you inject contrast through the balloon’s lumen. Now — with the blood flow arrested — your contrast stays longer, and you get a much clearer look. It’s like slowing down a rushing river just enough to see what’s inside.

Alright, moving back to the AVM nidus.

When it comes to MRI, personally I’m a big fan of T2-weighted images.

Because on T2, flowing blood shows up as jet black signal voids, while CSF is bright white. It gives you this really nice contrast. The black tangled vessels against the bright background — it just pops out at you.

And when you find the nidus, the next question is — where exactly is it?

Is it MCA territory? ACA? PCA?

Because depending on that, you can start classifying your feeders.

If the feeder comes from the territory where the nidus sits — it’s a direct feeder. If it comes from another territory — usually through collaterals — it’s an indirect feeder.

Let’s say you have an AVM in the parietal lobe — supplied mainly by the MCA, but also getting a bit from the ACA.

In this case:

• ​ MCA = direct feeders.
• ​ ACA = indirect feeders.

And the ACA feeders usually reach the nidus through pial collaterals.

And understanding this is super important when planning your treatment.

Alright, that’s the anatomy part pretty much wrapped up. Next — we’ll jump into treatment strategy — why treating an AVM is kinda like eating an apple.

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