A Traumatic Brain Injury is either diffuse or focal.
TRAUMATIC BRAIN INJURY: Diffuse Injuries
Diffuse injuries are characterized by microscopic damage to many areas of the brain; whereas, focal injuries occur in a specific location of the brain.
TRAUMATIC BRAIN INJURY: Focal Injuries
Focal injuries with localized damage to the brain may result when the brain bounces against the skull. The areas of the brain that are most likely affected by focal injury are the brainstem, frontal lobe, and temporal lobes because their locations are close to bony protrusions.
As a result of the traumatic brain injury, the brain may experience: chemical cascade, energy crisis, and diffuse axonal injury.
Diffuse Axonal Injury (DAI)
Diffuse Axonal Injury (DAI) is one of the most common and devastating types of TBIs. The damage is done in the form of lesions in white matter tracts over large areas. DAI occurs when the nerve cells in the brain are torn apart. Diffuse axonal injury is the “hallmark” of mTBI and concussion. However, diffuse axonal injury can occur in every degree of severity, and with severe DAI, the outcome is often a coma with over 90 percent of patients never regaining consciousness. Those who do are usually significantly impaired. DAIs are often the result of traumatic shearing forces or strong rotational forces, which occur when the head is accelerated or decelerated very quickly, such as in car accidents. The unmoving brain lags behind the movement of the skull, causing the brain to tear. When there is extensive tearing of nerve tissue throughout the brain, the brain’s regular communication and chemical processes can be disrupted. This “chemical cascade” can cause additional injury.
Damage to Neuronal Firing
Damage to neuronal firing in the brain can also result. The brain is comprised of billions of cells. The basic cell is the neuron, which conducts electrochemical impulses that transmit information in the brain and throughout the central nervous system. Neurons are comprised of the cell nucleus with multiple branching dendrites that receive information from other neurons, and the axon that carries the electrical nerve impulses for transmission to connecting neurons. Information from one neuron flows to another neuron across a synapse. The synapse contains a small gap separating neurons. The synapse consists of: a presynaptic ending that contains neurotransmitters, mitochondria and other cell organelles.
Abnormal neuronal firing can occur when the signals between neurons are disrupted. This occurs when there is “axonal shearing” which involves the connection of the axon being “sheared” from the cell body by trauma forces.
As a result of the damage to neuronal firing, the symptoms of Diffuse Axonal Injury include slow mental processing, in which the injured victim requires increased time to hear what is being said, increased time to process that information, and increased time to formulate and articulate a response.
Image of Neuron and Synapse