By Dr Ananya Mandal, MD
Head trauma refers to any damage to the scalp, skull or brain caused by injury. Examples of the types of damage that may be seen in cases of head trauma include neuronal injury, vascular injury, hemorrhage and cranial nerve injury.
The two main types of lesion that occur in head trauma are primary lesions and secondary lesions. Primary lesions occur as a direct result of initial injury to the head causing displacement of the physical brain structures. Secondary injuries occur over time and may involve several cellular processes rather than mechanical damage. Secondary lesions can occur as a result of the primary lesion or they may be unrelated to it.
Primary injury is injury that occurs as a direct result of the initial head trauma. Examples of primary injury include contusion (bruising or hematoma), vascular damage, and axonal shearing (torn and stretched nerve axons). Primary injury can damage the blood–brain barrier and meninges and lead to neuronal death, which may occur in a random manner. Different brain areas may sustain different levels of damage depending on their sensitivity to mechanical loading.
Secondary injury can occur as a result of the primary injury due to complications such as inadequate bloodflow in the brain (ischemia), reduced availability of oxygen (hypoxia) in the brain, low blood pressure, increased intracranial pressure (pressure inside the skull), and swelling in the brain (cerebral edema).
Other causes of secondary injury include meningitis, brain abscess, increased carbon dioxide levels, free radical damage, and acidosis.
Reviewed by Sally Robertson, BSc
Last Updated: Aug 6, 2014