Unilateral Internal Carotid Artery Agenesis Incidentally Detected on Trauma CT Angiography: A Case Report and Diagnostic Considerations
This case report describes a 32-year-old man with congenital agenesis of the left internal carotid artery, incidentally identified on trauma CT angiography by the absence of the bony carotid canal, highlighting the critical importance of distinguishing this rare anomaly from acquired occlusion to guide clinical management and future procedural planning.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Imagine your brain is a bustling city that never sleeps, and the roads delivering its fuel (blood) are the Internal Carotid Arteries. Usually, this city has two main highways, one on the left and one on the right, running from the neck up into the skull. But in a rare twist of nature, sometimes one of these highways was never built in the first place.
This is the story of a 32-year-old man who walked into a hospital after a very bumpy ride. He was a passenger in a car that flipped over at high speed, hitting a utility pole. It was a chaotic scene: a torn-up scalp, a deep cut on his arm, and some cracked ribs. But while the doctors were patching him up, they ran a special "traffic camera" scan of his head and neck called a CT Angiography.
The Big Discovery
The scan revealed something surprising: the left "highway" (the left internal carotid artery) was completely missing. It wasn't just blocked; it was as if the road had never been paved.
Here is the crucial part where the paper draws a hard line: This was not an accident. The doctors didn't think the crash broke the road. They knew this because they looked at the "tunnel" the road usually runs through inside the skull bone. In a normal person, there is a bony tunnel called the carotid canal. In this patient, that tunnel was missing.
Think of it like this: If a highway is blocked by a landslide (an injury or a clot), the tunnel underneath the mountain is still there, just clogged. But if the highway was never built, the tunnel was never dug. Since the tunnel was gone, the doctors knew this was a congenital agenesis—a fancy way of saying "born without it." This ruled out the idea that the car crash caused the problem.
How the City Survived
You might wonder, "If a main road is missing, doesn't the city starve?" Not in this case. Because the man was born this way, his brain had spent his whole life building clever detours. It was like a city that learned to use side streets and bridges to keep traffic flowing.
The scan showed that blood was sneaking in from the right side, crossing over the middle of the brain, and even coming up from the back (the vertebrobasilar system). These detours were so good that the man had no symptoms and no neurological problems, even before the crash.
The Hidden Risk
While the man was lucky to have no symptoms, the paper points out that this setup isn't entirely "benign" (harmless). Because the blood has to take these detours, the side streets are working harder than usual. The paper notes that this extra pressure can wear down the walls of the blood vessels over time.
In fact, the paper suggests that people with this missing artery have a much higher chance of developing a "balloon" (an aneurysm) on their blood vessels later in life compared to the general population. The paper doesn't say this man has an aneurysm—he didn't—but it says the risk is real enough that he needs to be watched.
The Plan
Because of this, the doctors gave him a specific game plan:
- Medication: He started taking a daily aspirin to keep his blood flowing smoothly and a statin to keep his cholesterol low, just to be safe.
- Surveillance: He needs to get a special brain scan (MRA) in five years to check if any of those "balloons" have started to form.
- Future Warning: He was told to tell any future doctors or surgeons about his missing artery. If he ever needs brain surgery or anesthesia, the doctors need to know the "map" is different so they don't accidentally cut into a vital detour.
The Takeaway
This case is a reminder that when doctors see a missing road on a scan, they shouldn't just assume it's a crash. They need to check the "tunnel" in the bone. If the tunnel is gone, it's a birth defect, not a trauma. Recognizing this difference changes everything: it stops doctors from panicking about a fresh injury and starts them planning for long-term safety.
The paper confirms that while this condition is incredibly rare (less than 0.01% of people), spotting it in a trauma patient is a golden opportunity to prevent future problems. The man went home with a few stitches and a new plan, but his brain's clever detours kept him safe.
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