Immediately following TBI, two types of effects are seen. First, brain tissue reacts to trauma and to tissue damage with a series of biochemical and other physiological responses. Substances that once were safely housed within the cells now flood the brain. These processes further damage and destroy brain cells, in what is called secondary cell death.
The second type of effect is seen in the individual’s functioning. For those with more severe injuries, loss of consciousness (LOC) occurs at the time of trauma, lasting from a few minutes or hours to several weeks or even months. Lengthy LOC is referred to as coma. In such serious injuries, the first few days after trauma may also produce negative changes in respiration (breathing) and motor functions.
As an individual regains consciousness (those with the severest injuries may never do so), a variety of neurologically based symptoms may occur: irritability, aggression and other problems. Post-traumatic amnesia (PTA) is also typically experienced when an injured person regains consciousness. PTA refers to the period when the individual feels a sense of confusion and disorientation – Where am I? What happened? – and an inability to remember recent events.
As time passes, these responses typically subside, and the brain and other body systems again approach physiological stability. But, unlike tissues such as bone or muscle, the neurons in the brain do not mend themselves. New nerves do not grow in ways that lead to full recovery. Certain areas of the brain remain damaged, and the functions that were controlled by those areas may emerge as challenges in the individual’s life.