Secondary injury is usually the result of hypoxic-ischemic injury caused by cerebral edema. Because the soft and pliable brain is enclosed within the rigid skull, abnormal brain fluid dynamics caused by cerebral edema result in increased intracranial pressure (ICP). Signs and symptoms of increased ICP include headache, loss of sense of smell, and altered level of consciousness. Even a mild increase in ICP is sufficient to cause death of neural tissue caused by inadequate perfusion. Moderate and severe increases in ICP can cause brain tissue to shift position or herniate from one chamber into another and may also cause compression of neural structures. Intracranial hematoma (epidural, subdural, and intracerebral) are another source of secondary
