Head injury or Traumatic Brain Injury (TBI) occurs when a sudden physical assault on the head causes damage to the brain. The damage can be focal, confined to one area of the brain, or diffuse, involving more than one area of the brain. Head injuries can result from a closed head injury or a penetrating head injury.
A closed head injury occurs when the head suddenly and violently hits an object, without the object breaking through the skull. A penetrating head injury occurs when an object pierces the skull and enters the brain tissue.
Several types of traumatic injuries can affect the head and brain. A skull fracture occurs when the bone of the skull cracks or breaks. A depressed skull fracture occurs when pieces of the broken skull press into the tissue of the brain.
This can cause bruising of the brain tissue, called a contusion. A contusion can also occur in response to shaking of the brain within the confines of the skull, an injury called "contrecoup".
Shaken baby syndrome is a severe form of head injury that occurs when a baby is shaken forcibly enough to cause extreme contrecoup injury. Damage to a major blood vessel within the head can cause a haematoma, or heavy bleeding into or around the brain.
The severity of a head injury can range from a mild concussion to the extremes of coma or even death. A coma is a profound or deep state of unconsciousness.
Symptoms of a head injury may include headache, nausea, confusion or other cognitive problems, a change in personality, depression, irritability, and other emotional and behavioural problems. Some people may have seizures as a result of a head injury.
CT scanning is the gold standard for the radiologic assessment of a head-injured patient. A CT scan is easy to perform and is an excellent test for detecting the presence of blood and fractures, which are the most important lesions to identify in emergency situations.
Plain x-rays of the skull are recommended by some people as a way to evaluate patients with only mild neurologic dysfunction. However, most large centres in South Africa have readily available CT scanning, which is a more accurate test. For this reason, the routine use of skull x-rays for head-injured patients has declined.
Magnetic resonance imaging (MRI) is not commonly performed for acute head injury because it takes longer to perform than a CT scan, and because transporting an acutely injured patient from the emergency room to the MRI scanner is difficult.
However, after a patient has stabilised, MRI may demonstrate the existence of lesions that could not be detected by CT. Such information is generally more useful for determining prognosis than for influencing treatment.
The outcome of TBI depends on the cause of the injury and on the location, severity, and extent of neurological damage: outcomes range from good recovery to death. Doctors often use the Glasgow Coma Scale to rate the extent of injury and chances of recovery.
The scale (3-15) involves testing for three patient responses: eye opening, best verbal response, and best motor response. A high score indicates a good prognosis and a low score indicates a poor prognosis.
Like all trauma patients, persons with head injury need a systematic yet rapid evaluation in the emergency room. Cardiac and pulmonary functions are the first priority. Next, a rapid examination of the entire body is performed. Immediate treatment for head injuries involves surgery to control bleeding in and around the brain, monitoring and controlling intracranial pressure, insuring adequate blood flow to the brain, and treating the body for other injuries and infection.
To consider, some contusions or haematomas may enlarge over the first hours or days after head injury, so that some patients are not taken to surgery until several days after an injury. Sometimes these delayed haematomas are discovered when a patient's neurologic exam worsens or when the ICP increases.
On other occasions, a routine follow-up CT scan that was ordered to see if a small lesion has changed in size indicates that the haematoma or contusion has enlarged significantly. In many of these cases, removing the lesion before it enlarges and causes neurologic damage may be safest for the patient.
Reviewed by Dr Andrew Rose-Innes, Assistant Professor of Neurology, University of Washington.