Such generalized axonal damage is known as diffuse axonal injury. This refers to bleeding within the brain as it scrapes across the inner surface of the skull. This results when arterial blood enters the potential space between a membrane which covers the brain, the dura mater, and the inner surface of the skull. The result is a localized collection of blood on the outside of the brain. A large epidural hematoma can lead to death through increased intrcranial pressure and herniation, which occurs when the brainstem is pushed down from above.
Immediate surgery can be life-saving.
This results when venous blood enters the space beneath the dura mater and the arachnoid membrane. Elderly and alcoholic patients are particularly prone to subdural bleeding. Similar to epidural hematoma, a large subdural hematoma can be life-threatening without surgery. In instances of severe head injury convulsive seizures can develop as a result of the injury. Often these seizures will develop months or years after the actual injury.