Every brain injury is different. The frontal lobes and temporal lobes can be susceptible to injury because of the location of bone near the brain. The frontal lobes are particularly important for planning, organization, problem-solving, memory, impulse control, decision-making, selective attention, and control of behavior and emotions. The temporal lobes are located on the sides of the brain behind the temporal lobes and near the level of the ears. The temporal lobes are responsible for processing speed (speed of thinking), understanding and producing speech, and various aspects of memory. You will notice that a lot of these tasks are important for completing activities of daily living and remaining functional at work and school. It is also important to note that other areas of the brain work in concert with the temporal lobes and influence the above abilities. Most common after moderate to severe brain injury is injury to the inferior frontal lobe and anterior (or front) temporal lobe.
The hippocampus (or, plural, hippocampi) are other important structures that are very sensitive to oxygen loss or lower blood flow. I have previously assessed individuals with hippocampal damage as a result of anoxic or hypoxic injuries (where the brain does not receive the oxygenated blood that it needs). This can result in damage to these structures. Injury may affect new memory creation, new memory retention, mood, and orientation. It is as if some individuals with this injury live in a “1-minute time zone.” They may not be able to remember what they told you moments ago.
Most brain injuries are mild, but approximately 20% are classified as moderate or severe. It is important to remember, though, that brain injury is the total effect of both primary injury (damage to brain tissue) and secondary causes of TBI. Diffuse axonal injury is a term that refers to damage to corpus callosum and midline structures such as the parasaggital white matter, intraventricular septum, walls of the third ventricle, and brain stem. It can be responsible for initial loss of consciousness, and results from acceleration and deceleration forces in high velocity impact. Axonal injury can occur because of problems with transport in the axon, causing swelling and shearing/tearing. Sometimes diffuse axonal injury or DAI won’t show up on an initial CT, but you can see it on follow-up CT or MRI. You may be able to see microtears.
One term you can see with brain injury is “midline shift.” This is a term seen in radiology readings after someone experiences a subdural hematoma, or pool/collection of blood in the brain after injury. The blood will push against the brain and can require surgery where blood pushes the brain to 1 side. Subdural hematoma can occur due to tearing of bridging veins or directly from contusion. It can be chronic in older patients. It can require brain surgery (“evacuation”) if there are signs of “midline shift.”
Subarachnoid hemorrhages can occur in frontal-temporal injuries. With this injury, blood vessels can spasm, which increase the risk of secondary injury. There can be an increased risk of hydrocephalus.
An epidural hematoma can also be found. It is very important to treat these injuries early, to reduce mortality. The celebrity Natasha Richardson had this type of injury.
There are some early predictors of outcomes at the time of injury. The person’s rating on the Glasgow coma scale, length of coma, length of posttraumatic amnesia, age, pupil reflex, prior insults to the brain, neuroimaging findings, and psychosocial factors all play a role in recovery. People with reactive pupils at time of injury have better outcomes than those who do not. People are even using sideline assessments such as the blink reflexometer to track this; however, this is an emerging technology and is not well validated for use in this population. The biopsychosocial model (where psychological and social factors are taken into consideration) still has the strongest of supports for predicting outcomes, particularly in cases of milder brain injury.
The Glasgow Coma Scale (GCS) is among the most widely used and well known assessment tools used after brain injury. The GCS after mild TBI is 13-15. The GCS after moderate TBI is 9-12. The GCS after severe TBI is 3-8. This measure is administered in the ER and helps people define the severity of injury.
Length of posttraumatic amnesia (PTA) is a very important predictor of outcomes as well. Posttraumatic amnesia is the period during which the patient’s ability to learn new information (lay down new daily memories) is minimal or nonexistent. It ends when the patient incorporates ongoing daily events into memory and is able to lay down new day to day memories. There is another scale called the Galveston Orientation and Amnesia Test (GOAT) which can be used to assess this in the ER. If PTA is less than 2 months a person with brain injury has a better chance of improved outcomes than PTA greater than 2 months.
After brain injury it is important for qualified professionals to establish whether the brain injury is mild, moderate, or severe, and to predict prognosis (both in terms of level of functioning, return to work, cognitive and behavioral/emotional outcomes). People with brain injury, particularly severe brain injury, may benefit from caregiver support, discussion of life changes, discussion of intimacy after brain injury (couples), determination of whether educational and workplace accommodations may be of benefit, exploration of disability benefits, vocational rehabilitation, and work with a rehabilitation team. It is important to remember that mild and severe brain injuries are very different injuries that can require a very different level of supports.