Intracranial hemorrhage

An intracranial hemorrhage is a hemorrhage, or bleeding, within the skull. Intracranial bleeding occurs when a blood vessel in the head is ruptured or leaks. It can result from physical trauma (as occurs in head injury) or nontraumatic causes (as occurs in hemorrhagic stroke) such as a ruptured aneurysm (ballooning blood vessel).

Intracranial hemorrhage is a serious medical emergency because the buildup of blood within the skull can lead to increases in intracranial pressure, which can crush delicate brain tissue or limit its blood supply. Intracranial bleeds with a lot of bleeding are more dangerous than those with not as much blood.

CAT scan (computed axial tomography) is the definitive tool for accurate diagnosis of an intracranial hemorrhage.

Types of intracranial hemorrhage are roughly grouped into intra-axial and extra-axial.

Intra-axial hemorrhage
Intra-axial hemorrhage is bleeding within the brain itself. This category includes Intraparenchymal hemorrhage, or bleeding within the brain tissue, and intraventricular hemorrhage, bleeding within the brain's ventricles (particularly of premature infants).

Extra-axial hemorrhage
Extra-axial hemorrhage, bleeding that occurs within the skull but outside of the brain tissue, falls into three subtypes:
 * Epidural hemorrhage is caused by trauma, and results from laceration of an artery, most commonly the middle meningeal artery. This is a very dangerous type of injury because the bleed is from a high-pressure system and deadly increases in intracranial pressure can result rapidly.
 * Patients have a loss of consciousness (LOC), then a lucid interval, then sudden deterioration (vomiting, restlessness, LOC)
 * Head CT shows lenticular (convex) deformity.
 * Subdural hemorrhage results from tearing of the bridging veins in the subdural space between the dura and arachnoid mater.
 * Head CT shows crescent-shaped deformity
 * Subarachnoid hemorrage, like intraparenchymal hemorrhage, can result either from trauma or from ruptures of aneurysms or arteriovenous malformations. Blood is seen layering into the brain along sulci and fissures, or filling cisterns (most often the suprasellar cistern because of the presence of the vessels of the circle of Willis and their branchpoints within that space). The classic presentation of subarachnoid hemorrhage is the sudden onset of a severe headache. This can be a very dangerous entity, and requires emergent neurosurgical evaluation, and sometimes urgent intervention.