Chapter 80 Traumatic Brain Injury
PATHOPHYSIOLOGY
Traumatic brain injury (TBI) is a common injury in children and the most common cause of traumatic death. TBI is often caused by a primary injury, and is followed by a secondary injury. The primary injury is the actual trauma itself, because it occurs at the time of impact on the central nervous system and may cause damage and/or death to the brain cells. A hypoxic insult may also cause a primary injury. The secondary injury is caused by the brain’s response to the trauma and evolves over a period of hours to days after the injury. The secondary injury can result in the loss of cerebral autoregulation, development of cerebral edema, and breakdown of the blood-brain barrier. The secondary injury is exacerbated by systemic hypotension or hypertension, ischemia, hypoxia, or hypercapnia.
There are several types of brain injury:
1. Open head injuries are caused by bullets or other penetrating objects, which include but are not restricted to depressed skull fracture(s) with scalp laceration.
2. Closed head injuries are the more common of the two and usually are caused by a rapid movement of the head, during which the brain is forced back and forth within the skullcap. Such injuries are commonly found in motor vehicle crashes, falls, and recreational sports related activities (i.e., football, bicycling).
Brain injuries are also commonly classified in terms of severity (i.e., mild, moderate, severe).
1. Mild brain injury (Glasgow Coma Scale: 13–15) is commonly referred to as a concussion, which may involve a brief loss of consciousness, loss of memory of events immediately preceding and/or following the injury, alteration in mental status at the time of the injury, and/or neurologic deficits that may or may not be transient. Characteristics most common of mild brain injury include physical, cognitive, and/or behavioral, and are listed below.
2. Moderate brain injury (Glasgow Coma Scale: 8–12) results in a loss of consciousness lasting from minutes to hours, followed by days and/or weeks of confusion. This is usually associated with physical, cognitive, and/or behavioral impairments, which may be transient or permanent.
3. Severe brain injury (Glasgow Coma Scale: <8 for at least 6 hours after injury) always results in prolonged loss of consciousness or coma lasting from days to sometimes months, depending on the severity and location of the injury. Diffuse axonal injury (DAI) is a common finding in severe brain injuries on radiographic investigation. DAI is defined as impaired function and gradual loss of some axons, which are the long extensions of a nerve cell that enable such cells to communicate with each other and integrate global function. Such injuries may leave patients with severe and permanent disabilities involving physical, cognitive, and/or behavioral impairments.
INCIDENCE
1. Males are twice as likes as females to suffer head injuries.
2. Concussions are the most frequent type of TBI.
3. Among children ages 0–14 years, 475,000 TBIs occurred each year between 1995 and 2001 in the United States. Of those, 435,000 children were treated for TBI in the emergency department (ED) each year, 37,000 were hospitalized, and 2685 died.
4. TBI is the leading cause of acquired disability in childhood.
5. Causes of TBI vary with age: very young children ages 0 to 4 years had the highest rate of TBI-related ED visits (1035.0 per 100,000 population).
6. Posttraumatic seizures develop in 7% to 12% of children with cerebral contusions.
7. Exposure to guns and access to a loaded firearm increase the risk of unintentional brain injury and death in a child. The unintentional death rate among children 14 years of age and younger is 9 times higher in the United States than in 25 other industrialized countries combined.
CLINICAL MANIFESTATIONS
2. Headache, dizziness, light-headedness, or loss of balance
3. Bleeding or clear drainage from laceration, nose, or ears
6. Irritability and agitation, sleep problems, fatigue, anxiety, depression, emotional lability
7. Loss of consciousness or cognitive impairment, decreased attention span, concentration or mental speed; short-term memory loss
8. Focal deficit including impaired motor function of limbs such as hemiparesis or hemiplegia
9. Decorticate or decerebrate posturing
10. Battle sign—bruising behind ear
11. Raccoon sign—bruising around eyes
12. Increased sensitivity to lights, sounds, or distractions
COMPLICATIONS
Depending on the type, severity, and location of the head injury, deficits may be multiple and include motor, communicative, cognitive, sensory, behavioral, and emotional problems or delay in reaching developmental milestones not yet achieved. A variety of complications involving the nervous system and other organ systems may be seen. These complications can occur from either the primary or secondary injury to the brain.
Primary Brain Injury
Traumatic brain injury (TBI) is defined as a physiologic disruption of brain function resulting from both external (an object striking the head or the head striking an object) and/or internal trauma (the rapid acceleration/deceleration of the brain within the skullcap).
Primary injuries include the following:
1. Concussion results from shearing and stretching forces in the brain that produce no structural damage. This is the least serious type of injury that requires close monitoring for complications. With a concussion, the child usually has a momentary loss of consciousness. Recovery generally takes place within 24 hours, with a return to the preinjury level of activity and orientation.
