Traumatic Brain Injury is defined as an alteration in brain function, or other evidence of brain pathology, caused by an external force.
A blow to the head is the most common cause of TBI. It can happen from falls, motor vehicle crashes, assaults, sports, injuries, and other accidents.
An object penetrating the skull is a less common one but can be serious. It can happen from gunshot wounds, shrapnel from explosions, or other objects that pierce the skull.
Rapid acceleration or deceleration of the head can happen in car accidents, falls, or other situations where the head is jerked forward or backward suddenly.
Falls is the leading cause of TBI
Primary Injury is due to direct trauma to the parenchyma.
Secondary Injury results from a cascade of biochemical, cellular, and molecular events that evolve overtime due to the initial injury and injury-related hypoxia, edema, and elevated intracranial pressure (ICP).
Primary Brain Injury results from either brain tissue coming into contact with an object or rapid acceleration/deceleration of the brain creating cortical disruption.
Coup is when an object strikes the head, the brain tissue directly under the impact site is bruised and damaged.
Countercoup is as the brain bounces back inside the skull after the impact, it can hit the opposite side of the skull, causing damage at that location. This is like the brain sloshing back and forth inside the skull.
Common areas of focal injury includes:
Anterior temporal poles
Frontal poles
Lateral and inferior temporal cortices
Orbital cortices.
Acceleration is a direct blow to the head and the skull moves away from force. Brain rapidly accelerates from stationary to in-motion state causing cellular damage.
Deceleration is when head impacts to a stationary object like car windshield. Moving skull stops motion almost immediately buy the brain floating in cerebral spinal fluid briefly continues moving in skull towards direction of impact, resulting in significant forces that damage cells.
Blast Injury is when an explosive device denotes, a transient shock wave is produced, which can cause brain damage.
Diffuse axonal injury is the predominant mechanism of injury in most individuals with severe to moderate TBI. It is common in high-speed motor vehicle accidents and can be seen in some sports-related TBIs.
Primary blast injury results from the direct effect of blast overpressure in the brain.
Secondary injury results from shrapnel and other objects being hurled at the individual.
Tertiary injury occurs when the victim is flung backward and strikes an object
Concussion is a loss of consciousness, either temporary or permanent, resulting from injury or blow to head.
Mild Concussion Syndrome is a momentary loss of consciousness or confusion after TBI. May see retrograde amnesia.
Classical Concussion is moderate in severity with loss of consciousness that is transient and mostly reversible in 24 hours. May see both retrograde and post-traumatic amnesia, temporary lethargy, irritability, and cognitive dysfunction.
Severe Concussion if LOC is longer than 24 hours. It is associated with diffuse axonal injury and coma.
Cerebral Contusion is bruising of the brain and breakdown of small vessels and extravasation of blood into the brain.
Secondary Brain Injury occurs as a result of a chain of cellular events that follow tissue damage in addition to the secondary effects of hypoxemia, hypotension, ischemia, edema, and elevated ICP.
Hypoxic-ischemic Injury results from a lack of oxygenated blood flow to the brain tissue. It can be caused by systemic hypotension, anoxia, or damage to specific vascular territories of the brain.
Normal ICP is 4 – 15 mmHg / 5 – 10 mmHg
With TBI is ICP = >20 mmHg
Epidural Hematoma accumulates in the space between bone and Dura. Almost always associated with a skull fracture. Most common site is temporal bone.
Subdural Hematoma when acute – accumulates in the space between the Dura and the arachnoid, and in chronic – usually occur in the elderly. Most common cause is trauma.
Vegetative State is when the eyes may be open, though awareness of surroundings is absent.
Stupor is an unresponsive state from which the patient can be aroused only briefly with vigorous, repeated sensory stimulation.
Obtunded is when patients sleeps often and when aroused exhibits decreased alertness and interest in the environment and delayed reactions.
Glasgow Coma Scale is the most widely used clinical scale that helps define and classify the severity of injury.
Scores of 8 or less are classified as severe.
Scores between 9 and 12 are defined as moderate.
Scores of 13 to 15 are classified as mild.
No Response is when patient appears to be in deep sleep and is completely unresponsive to any stimuli.
Generalized Response is when patient reacts inconsistently and non-purposefully to stimuli in a nonspecific manner.
Localized Response is when patient reacts specifically but inconsistently to stimuli.
Confused-Agitated is when patient is in a heightened state of activity. Behavior is bizarre and non-purposeful relative to immediate environment.
Confused-Inappropriate is when patient is able to respond to simple commands fairly consistently. However, with increased complexity of commands or lack of any external structure, responses are nonpurposeful, random, or fragmented.