Phase 1 · Understand the Body — Why the disease behaves the way it does.
The One-Line Truth
The whole disease in one chain
Everything on this page exists to explain this line.
Bleeding inside the skull can happen in four spaces—inside brain tissue (intracerebral), around the surface of the brain (subarachnoid), between the brain and the dura (subdural), or between the dura and the skull (epidural)—and where the blood lands tells you what broke and what to do.
Water Balloon in a Locked Box
Imagine your skull is a rigid plastic box with three things inside: a sponge (brain tissue), a network of tiny pipes (blood vessels), and clear gel (cerebrospinal fluid)—they fill exactly 100% of the space with no room to spare. Now a pipe bursts and water (blood) starts pooling inside the box. The sponge gets squeezed, the gel gets pushed out through a drain (the spinal canal), and the pipes get kinked. For a while the box seems fine because it's squishing things around inside, but once there's nowhere left to push things, pressure inside skyrockets and the sponge starts to bulge out through the drain hole (herniation). The water (blood clot) is like a tumor—it doesn't matter what it's made of, only that it takes up space the brain needs to survive.
American Heart Association / American Stroke Association Guidelines for the Management of Spontaneous Intracerebral Hemorrhage (2022) · American Heart Association / American Stroke Association Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage (2023) · Neurocritical Care Society · CDC Stroke Facts · reviewed 2026-07-07