Traumatic brain injuries (TBI) are generally defined as injury to the brain caused by an external source. TBI are classified as acquired brain injuries in that they occur after birth and traumatic in that damage is caused by force or penetration rather than internal injury such as stroke or aneurysm. They are most often classified by mechanism of injury, severity, and anatomical area of the injury. The most common injury to the brain results from pressure caused by swelling or bleeding into the cranial cavity.
Traumatic brain injuries are a leading cause of death and disability around the world. The leading causes of TBI are firearms and vehicle accidents with the majority of firearm injuries resulting from suicide attempts. Worldwide between 70-90% of TBI treated are classified as mild. Men suffer TBI nearly twice as often as women; however women are more likely to have a poor outcome. Firearm injuries have the lowest survival rate at 9%.
Signs and symptoms vary according to the severity of the injury. Mild TBI symptoms include loss of consciousness for a few seconds to minutes, headache, nausea, vomiting, ringing in the ears, and dizziness. Moderate to severe injury results in repeated vomiting, confusion, agitation, blown pupils, slurred speech, and inability to awaken.
The basis for determining the severity of TBI is the Glasgow Coma Scale which rates a person’s level of consciousness on a scale from 3-15. A score between 13-15 indicates mild TBI and a more favorable outcome. Scores between 9-12 denote moderate damage and a score between 3-8 points to severe damage and a poor outcome. Other diagnostic models also take into consideration the duration of post trauma amnesia and duration of loss of consciousness.
Diagnostic tests used include computed tomography (CT), magnetic resonance imaging (MRI), X-rays, and angiography. CT scans are the most widely used diagnostic tool in an emergency situation although MRI’s often reveal greater detail. X-rays are used less often and angiography is most often used to help detect blood vessel trauma.
Immediately following a traumatic brain injury the primary focus in treatment is insuring adequate oxygen supply, controlling raised intracranial pressure, and maintaining proper cerebral blood flow. Cranial pressure can be relieved using a catheter or by opening the skull and the patient is usually intubated to assure adequate oxygen supply. TBI can also result in cardiac arrhythmia and pulmonary edema. These conditions are monitored and treated as needed.
Prognosis is dependent on the severity, mechanism of injury and time between injury and access to specialized care. The effects of mild TBI usually resolve within about three weeks while some degree of permanent disability is nearly 100% in cases of severe traumatic brain injury. The most common residual effects are loss of memory, behavioral and intellectual deficits, and convulsions.