Traumatic brain injuries remain a common cause of disability and death in the United States. An estimated 1.7 million adults and children in the United States sustain a traumatic brain injury each year, resulting in approximately 52,000 deaths, reports the Centers for Disease Control and Prevention. Traumatic brain injuries can have transient or permanent effects on the brain, depending on the nature and severity of the injury.
Neuronal Metabolic Abnormalities
Mild traumatic brain injuries, or concussions, cause transient disturbances in brain function. The brain is composed of billions of nerve cells, or neurons, which interact with one another to accomplish the numerous voluntary and involuntary tasks of the brain. Jarring of the neurons by a sudden, violent blow to the head causes temporary metabolic abnormalities that manifest as disturbances in brain function.
Common symptoms of concussion include irritability, difficulties concentrating and thinking clearly, sleep disturbances, mental slowness, lack of energy, dizziness, clumsiness, anxiety and nervousness, reports the CDC. Recovery time varies from days to months, depending on the severity of the concussion.
Brain Bruising
High-energy blows to the head cause an impact between the brain surface and the skull, resulting in areas of brain bruising known as cerebral contusions. The bruises represent blood leakage into the brain tissues caused by rupture of minute blood vessels, or capillaries.
The neurons in an area affected by a brain contusion are injured by the impact. Connections to other nerve cells may be lost, interfering with the brain's normal communication networks. Neighboring nerve cells that were not initially injured may sustain secondary damage due to chemical imbalances initiated by the bruised neurons, explains the National Institute of Neurological Disorders and Stroke.
Symptoms associated with cerebral contusions are highly variable, depending on the area of the brain involved in the injury. Overall, cerebral contusions lead to similar but more severe disturbances in brain function than do concussions. Behavioral and personality changes often accompany damage to the frontal areas of the brain. Recovery time typically proves slower for a cerebral contusion compared to a concussion.
Cerebral Edema
Brain injuries often cause swelling of the brain tissue, the severity of which parallels the degree and extent of the trauma. The brain fits snuggly within the skull, leaving little room to accommodate tissue swelling. Substantial brain swelling, or cerebral edema, typically leads to increased pressure within the skull. The National Library of Medicine's MedlinePlus medical encyclopedia notes that markedly increased intracranial pressure is a medical emergency, as the brain may be squeezed through the bony opening at the base of the skull, fatally damaging the brainstem. Surgically opening the skull to relieve the pressure associated with cerebral edema usually averts this potentially lethal complication of severe brain injury.
References
- Centers for Disease Control and Prevention: How Many People Have TBI?
- National Institute of Neurological Disorders and Stroke: Traumatic Brain Injury: Hope Through Research
- Centers for Disease Control and Prevention: What are the Signs and Symptoms of Concussion?
- MedlinePlus: Brain Herniation
- University of Missouri Health Care: Cerebral Contusion
