Intracranial hemorrhage

What it means

The skull contains the brain and several thin protective layers, with small blood vessels running between them. When one of those vessels tears or bursts, blood collects somewhere it should not be. On a fresh CT scan this shows up as a bright white patch, which makes it one of the easiest things for radiologists to spot. On MRI, the appearance changes over days and weeks as the blood breaks down.

Why it appears on a CT or MRI report

Reports name the exact compartment where the blood sits — inside the brain tissue, on its surface, around the brain stem, or inside the fluid spaces. You will see descriptors for the size, the side, whether it is acute (new) or chronic (older), and whether there is surrounding swelling, mass effect, or midline shift. The named subtype (subdural, epidural, subarachnoid, intraparenchymal, intraventricular) tells the care team where the leak came from and how it usually behaves.

What it usually means

Even small bleeds inside the skull are taken seriously because they sit in a tightly enclosed space. A tiny, stable, older bleed in a person who feels well may be monitored conservatively. Larger or new bleeds are urgent: they can press on the brain, raise the pressure inside the skull, and worsen quickly in the first hours. Causes vary by age and situation — head trauma is the most common, followed by high blood pressure, an abnormal blood vessel (aneurysm or malformation), the side effects of blood-thinning medication, certain tumours, and occasionally no clear cause. The care team will look at the location, the size, the trajectory on repeat scans, and the person's symptoms to decide between observation, medication adjustments, or neurosurgery.

When to follow up

If this is a new finding on an emergency scan, the medical team is already acting on it. If you are reading the words on an outpatient report, treat it as something to discuss the same day with your doctor or the neurology team. Go to the emergency department immediately for sudden severe headache (often described as the worst of your life), repeated vomiting, sudden confusion or sleepiness, weakness on one side, slurred speech, vision changes, seizures, or a recent head injury followed by any of these symptoms.

A plain-language way to picture it

Imagine a sealed jar packed full of soft fruit. If you squeezed a little ink inside, there is nowhere for the ink to go without pushing the fruit aside. A bleed inside the skull does the same thing — even a small amount of blood takes up space that was already occupied, and the surrounding brain has to give way. That is why the size and location of the ink matter as much as the fact that it leaked at all.