In terms of the immediate events following TBI, two levels
of effects are seen. First, TBI is a physiological/biological event.
Brain tissue is damaged, sometimes severely; bleeding and swelling
within the brain may be found. The brain tissue reacts to trauma with
a series of biochemical and other physiological responses; substances
that once were safely housed within the cells now flood their former
'homes'. These events further damage and destroy brain cells, in what
is called secondary cell death.
The second level of effects is seen in the individual's
functioning. For those with more severe injuries, loss of consciousness
(LOC) occurs at the time of trauma, for anywhere from a few minutes
or hours to several weeks or even months. In such serious injuries,
the first few days after trauma may produce negative changes in body
systems other than neurological, for example, in respiration 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 a 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, nor do new nerves 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 be compromised
and emerge as challenges in the individual's life.
Before discussing in greater detail what happens to
the person after injury, which depends to a great extent on the severity
of injury, "severity" needs to be defined.
