Intracranial Hemorrhage
- Intracranial hemorrhage (ICH) just means blood somewhere inside the skull where it shouldn't be — the whole game is figuring out which compartment it landed in.
- On a non-contrast head CT, fresh blood is bright white. That brightness is the headline finding and the reason CT is the first stop in an emergency.
- The shape and location of the bright stuff tell you the cause: a rounded blob deep in the brain, blood tracing the surface grooves, or a smooth crescent or lens hugging the skull.
- Blood doesn't stay white forever — over days to weeks it fades, so the "age" of a bleed changes how it looks.
- The scary part usually isn't the blood itself but what it pushes on: swelling and shifting brain is the emergency hiding behind the bright spot.
Somewhere in your skull, blood is supposed to stay politely inside its pipes. Intracranial hemorrhage is what happens when it stops doing that and spills out into the cabin. The skull is a sealed, rigid box — wonderful for protecting the brain, terrible for accommodating an unexpected houseguest. There's no room to expand, so any leaked blood has to shove something else out of the way. That "shoving" is the part that hurts people.
The good news: blood is one of the easiest things in all of radiology to spot. The work is less "is there blood?" and more "where exactly is it, and what does that tell me?"
Why blood lights up like a flashbulb
On a non-contrast CT — the workhorse you'll order first for any head emergency (see the approach to the head CT) — fresh blood looks bright white. The reason is attenuation: the protein in blood, mostly from packed-together red cells, soaks up more of the X-ray beam than the surrounding brain. More beam eaten means brighter pixels.
Here's the catch nobody warns you about: that brightness is a fresh-blood phenomenon. As a clot ages over days and then weeks, it breaks down and gets less dense, fading from bright white toward gray and eventually toward the dark of spinal fluid. So a bleed you'd spot instantly today can become nearly invisible — even sneakily darker than brain — a couple of weeks later. Age changes the picture.
"Bright = acute" is a great rule of thumb, with one honest asterisk: very anemic patients have thin, watery blood that may look less impressively white. Don't talk yourself out of a real bleed just because it isn't the brightest thing you've ever seen.
Location is the whole story
Think of the inside of the skull as an apartment building with very specific rooms. Blood announces its cause by which room it floods. This is the single most useful framework for ICH, so it's worth a table.
| Where the blood sits | What it looks like | Classic cause |
|---|---|---|
| Inside the brain tissue itself (intraparenchymal) | A blob of white within the brain | High blood pressure; also tumors, malformations |
| In the spinal-fluid space over the surface (subarachnoid) | White tracing the grooves and cisterns, like spilled paint in the cracks | Ruptured aneurysm; trauma |
| The lens-shaped or crescent layers against the skull (epidural/subdural) | Smooth collection hugging the inner skull | Almost always trauma |
| Inside the fluid chambers (intraventricular) | White settling in the ventricles | Extension from another bleed |
The two surface collections that hug the skull — the lens-shaped one and the crescent — have their own dedicated page, because telling them apart is a rite of passage: see epidural and subdural hematoma. And when blood paints the surface grooves with no trauma to explain it, you're worried about a ruptured aneurysm until proven otherwise.
The deep brain bleed: blood pressure's calling card
The most common spontaneous bleed into the brain tissue is the hypertensive one. Chronically high pressure wears out the tiny deep arteries until one finally gives, typically in the deep central structures (the basal ganglia and thalamus) or the brainstem and cerebellum. On CT it's a white blob right where those structures live. It's the long-term cost of pressure the body quietly absorbed for years — like a hose left at full blast until a seam splits.
What actually makes it dangerous
The bright spot is rarely the thing that kills. The danger is mass effect: the leaked blood, plus the swelling that follows it, takes up space the skull can't provide. Structures get squeezed and pushed across the midline, and in the worst case brain tissue is forced through the few openings it has — the herniation syndromes. So when you find a bleed, your eyes immediately go to the neighbors: Is the midline shoved over? Are the fluid chambers being crushed or, conversely, ballooning because blood is blocking drainage?
A growing bleed can block the normal flow of spinal fluid and cause pressure to back up throughout the brain — a true neurosurgical emergency. Blood in the ventricles especially raises this flag. The clock starts the moment the blood appears, not when you finish describing it.
CT first, MRI for the backstory
CT wins the emergency because it's fast, everywhere, and brilliant at catching fresh blood. MRI enters later when you need the why: Was there a hidden tumor under that bleed? An old malformation? Has the patient had silent micro-bleeds for years? MRI is exquisitely sensitive to blood and its breakdown products, but it's slower and not the tool you reach for with a crashing patient in front of you.
Two classic traps. First, calcium — common in the normal pineal gland and choroid plexus — is also bright white on CT and can masquerade as blood; location and symmetry usually give it away. Second, don't anchor on a bleed and forget to check for an underlying ischemic stroke that bled into itself, which changes management entirely.
If you remember one thing: when you see bright white inside the head, name the room it's in. The compartment tells you the cause, the cause tells you the urgency, and the brain around it tells you how much time you have left.