Traumatic brain injury overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Joanna Ekabua, M.D. [2]
Overview
Traumatic brain injury (TBI) occurs when physical trauma causes brain damage. TBI can result from a closed head injury or a penetrating head injury and is one of two subsets of acquired brain injury (ABI). The other subset is non-traumatic brain injury, or injuries that do not involve external mechanical force (e.g. stroke, meningitis, anoxia). Parts of the brain that can be damaged include the cerebral hemispheres, cerebellum, and brain stem.
TBI can be mild, moderate, or severe, depending on the extent of the damage to the brain. TBI can cause a host of physical, cognitive, emotional, and social effects. Outcome can be anything from complete recovery to permanent disability or death.
Historical perspective
- There is limited knowledge on the historical perspective of traumatic brain injury.
Classification
- Traumatic brain injury may be classified as either
- Focal vs. diffuse
- Open vs. closed
- Mild, moderate or severe
Pathophysiology
- The progression of traumatic brain injury usually involves the inflammatory response pathway.
- Unlike most forms of traumatic death, a large percentage of the people killed by brain trauma do not die right away but rather days to weeks after the event. Rather than improving after being hospitalized, some 40% of TBI patients deteriorate. Primary injury (the damage that occurs at the moment of trauma when tissues and blood vessels are stretched, compressed, and torn) is not adequate to explain this degeneration. Rather, the deterioration is caused by secondary injury, a complex set of biochemical cascades that occur in the minutes to days following the trauma and contribute a large amount to morbidity and mortality from TBI.
- Secondary injury events are poorly understood but are thought to include brain swelling, alterations in cerebral blood flow, a decrease in the tissues' pH, free radical overload, and excitotoxicity. These secondary processes damage neurons that were not directly harmed by the primary injury.
Causes
- Common causes of traumatic brain injury include falls and Motor vehicle accident
Differentiating Traumatic Brain Injury from other Diseases
Traumatic brain injury must be differentiated from
- Concussion
- Chronic Traumatic Encephalopathy
- Extra-axial Hematomas
- Contusions
- Traumatic Subarachnoid Hemorrhage
- Diffuse Axonal Injury
Epidemiology and Demographics
Incidence
- The incidence of TBI varies by age, gender, region and other factors.
Age
- The age groups most at risk for TBI are children ages five to nine and adults over age 80.
Race
- There is no racial predilection to TBI
Gender
- Men are more commonly affected by TBI than women with a ratio of 2:1.
Region
- Each year in the United States:
- About two million people suffer a TBI
- About 500,000 people are hospitalized for TBI
- Approximately 270,000 people experience a moderate or severe TBI
- Approximately 60,000 new cases of epilepsy occur as a result of head trauma
- Approximately 50,000 people die from head injury
- Approximately 80,000 of these survivors live with chronic disabilities as a result of the injury.
Developed countries
- About sixty-nine million (95% CI 64–74 million) people worldwide sustain a TBI/year. The percentage of TBIs resulting from motor vehicle accident was minimal in North America (25%). The universal incidence of TBI per 100,000 people was significant in North America (1299 cases, 95% CI 650–1947) and Europe (1012 cases, 95% CI 911–1113).
Developing countries
- About sixty-nine million (95% CI 64–74 million) people worldwide sustain a TBI/year. The percentage of TBIs resulting from motor vehicle accident was significant in Africa and Southeast Asia (both 56%). The universal incidence of TBI per 100,000 people was minimal in Africa (801 cases, 95% CI 732–871) and the Eastern Mediterranean (897 cases, 95% CI 771–1023).
Risk factors
- Common risk factors for traumatic brain influry include male gender, age >55, driving without helmet and seatbelts, driving under the influence, conduct disorder, depression, and anxiety.
Natural History, Complications and Prognosis
Natural history
- If left untreated, 100% of patients with traumatic brain injury die.
Complications
- The results of traumatic brain injury vary widely in type and duration. A head-injured patient may experience physical effects of the trauma such as headaches, movement disorders (e.g. Parkinsonism), seizures, difficulty walking, sexual dysfunction, lethargy, or coma. Cognitive symptoms include changes in judgment or ability to reason or plan, memory problems, and loss of mathematical ability. Emotional problems include mood swings, poor impulse control, agitation, low frustration threshold, self-centeredness, clinical depression, and psychotic symptoms such as hallucinations and delusions.
Prognosis
- Traumatic brain injury is a frequent cause of major long-term disability in individuals surviving head injuries sustained in war zones. This is becoming an issue of growing concern in modern warfare, in which rapid deployment of acute interventions is effective in saving the lives of combatants with significant head injuries. Traumatic brain injury has been identified as the "signature injury" among wounded soldiers of the current military engagement in Iraq.
Diagnosis
History and Symptoms
- The hallmark of traumatic brain injury is finding a positive history of headache, mental confusion, lightheadedness, dizziness, double vision, repeated vomiting or nausea, seizures, inability to awaken, dilation (widening) of one or both pupils, slurred speech.
Physical Examination
- Common physical examination findings of traumatic brain injury include
- Neurologic deficit
- Motor and sensory skills
- Hearing and speech
- Coordination and balance
- Mental status
- Mood or behavior changes
- Normal to abnormal Glasgow Coma Scale (GCS).
- Head injured people with signs of moderate or severe TBI should receive immediate emergency medical attention.
Laboratory Findings
- An elevated concentration of CSF spectrin breakdown product (SBDP)120 and SBDP145, ubiquitin C-terminal hydrolase-L1 (UCH-L1), and glial fibrillary acidic protein (GFAP) is diagnostic of traumatic brain injury.
X Ray
- There are no x-ray findings associated with traumatic brain injury.