Carotid Disease
- Carotid disease is plaque building up in the carotid arteries — the two main pipes carrying blood up the front of your neck to your brain.
- The danger isn't usually the pipe slowly clogging; it's a chunk of plaque breaking off and sailing upstream to plug a brain vessel — a stroke.
- It almost always lives at the carotid bifurcation, where the common carotid splits into internal and external branches.
- Ultrasound with Doppler is the cheap, no-radiation first look; CTA or MRA confirms and measures how tight the narrowing is.
- The headline number everyone cares about is the degree of stenosis — how much of the channel is squeezed shut — because it drives whether someone gets surgery.
Imagine the plumbing that feeds your brain. Two big hoses run up the front of your neck — the carotid arteries — and they are, frankly, the most important pipes in the building. Carotid disease is what happens when gunk (atherosclerotic plaque, the same cholesterol-and-calcium sludge that clogs heart arteries) starts caking the inside of those hoses. The plot twist: the real catastrophe usually isn't the slow clog. It's a piece of that crusty buildup flaking off and getting whisked upstream into the brain, where it lodges in a vessel too small to pass and causes an ischemic stroke.
Why the bifurcation is always the scene of the crime
If carotid disease were a true-crime podcast, the location would be the same every episode: the carotid bifurcation, where the common carotid artery forks into the internal carotid (the one feeding the brain) and external carotid (face and scalp).
Why there? Blood flowing past a fork doesn't move in tidy parallel lines — it swirls and eddies, like water hitting the split in a river. That turbulence and shear stress irritate the vessel wall, and irritated walls are where plaque loves to set up shop. So when we image the carotids, our eyes go straight to the fork.
The artery we worry most about is the internal carotid, because that's the one plumbed directly into the brain. Plaque in the external carotid is far less scary — at worst it gives you a cold scalp's worth of trouble, not a stroke.
How we look: ultrasound first
The first-line test is a carotid ultrasound with Doppler. It's painless, radiation-free, and cheap — basically warm jelly and a wand on the neck. Grayscale ultrasound shows the plaque sitting on the wall; Doppler measures how fast blood is moving through the narrowed spot.
Here's the intuition: squeeze a garden hose and the water shoots out faster. Same with arteries — a tighter narrowing forces blood through a smaller gap, so it speeds up. We measure those velocities and use them to estimate how bad the stenosis is. Faster flow at the choke point generally means a tighter stenosis.
Confirming and measuring: CTA and MRA
Ultrasound is a great screen, but it's operator-dependent and can't always see high up where the artery dives toward the skull. So we confirm with cross-sectional CTA or MRA — angiography by CT or MRI. These give a clean roadmap of the whole vessel from chest to brain, let us actually measure the residual channel, and reveal plaque features and any narrowing the ultrasound couldn't reach.
The crucial output is the degree of stenosis: what fraction of the channel is squeezed shut, reported as a percentage. This number isn't trivia — it's the lever that decides treatment.
Why the percentage runs the whole show
Roughly, the management forks like this:
| Situation | What it usually means |
|---|---|
| Mild stenosis | Treat the plaque medically — statins, blood-pressure control, antiplatelet meds, lifestyle. Imaging surveillance over time. |
| Severe stenosis with symptoms (a recent stroke or TIA on that side) | Strongest case for a procedure to open or remove the plaque, on top of medical therapy. |
| Severe stenosis, no symptoms | More nuanced and genuinely debated; depends on the patient, surgical risk, and how good their medical therapy is. |
The two procedure options are surgically scraping the plaque out (carotid endarterectomy) or propping the vessel open with a stent. Which one, and whether to do anything at all, is a clinical decision — our job in imaging is to hand the team an accurate stenosis number and an honest description of the plaque.
A near-occlusion or a fully blocked carotid can fool you. When flow slows to a trickle, Doppler velocities can paradoxically drop — making a critically tight artery look deceptively mild on numbers alone. And a totally occluded internal carotid is not a surgical target. Always look at the grayscale image and the actual lumen, not just the velocity readout.
The one thing to carry out the door
Carotid disease is mostly a quiet plumbing problem until the day a flake of plaque breaks loose and travels to the brain. So when you see that fork in the neck, two questions matter above all: how tight is the narrowing, and has it already caused symptoms? Those two answers — the percent stenosis and whether there's been a stroke or TIA — are what turn a gray smudge on a screen into a real decision about someone's brain.