How do traumatic head injuries cause brain compression or bruising?

Traumatic head injuries cause brain bruising and compression through several mechanisms involving direct impact, rotational forces, and secondary complications.12

Brain Bruising (Contusion)

Bruising of the brain tissue, or contusion, typically occurs when a force causes the brain to shift or move within the skull.12
* Direct Impact: Blunt trauma causes injury directly beneath the point of contact.2
* Contrecoup Injury: The brain may bounce back and forth, striking the rough, bony base of the skull, which causes bruising on the side opposite the initial impact.12
* Tissue Shearing: Rotational energy and rapid velocity changes create shear stress, which can tear brain tissue and blood vessels, leading to internal bleeding and further damage.12

Brain Compression

Compression often results from the accumulation of blood or fluid within the rigid confines of the skull, which increases intracranial pressure.23
* Hematomas: Bleeding into the spaces surrounding the brain—such as the epidural space (between the skull and dura mater) or the subdural space—creates a mass that exerts pressure on the brain tissue.13
* Edema: Following an injury, the brain may swell due to inflammation or fluid leakage, further increasing pressure.2
* Consequences: If intracranial pressure becomes too high, it can force brain tissue to shift or herniate, which is a life-threatening condition.123