Typically, "severity of injury" refers to the degree of
presumed brain tissue damage. Degree of damage cannot be measured,
but instead is estimated by measuring the duration of loss of consciousness
and the depth of coma.
The scale most commonly used to measure the depth of coma is the Glasgow
Coma Scale (or GCS). The GCS is used to rate three basic aspects of
functioning: eye opening, motor response and verbal response. Individuals
in deep coma score very low on all aspects of functioning measured
with the GCS, while those recovering from coma score higher.
Glasgow Coma Scale |
| |
|
| Eye opening |
Spontaneous |
4 |
To speech |
3 |
To pain |
2 |
None |
1 |
| Best Motor Response |
Obeys |
6 |
Localizes |
5 |
Withdraws |
4 |
Abnormal flexion |
3 |
Extensor response |
2 |
None |
1 |
| Best Verbal Response |
Oriented |
5 |
Confused conversation |
4 |
Inappropriate words |
3 |
Incomprehensible sounds |
2 |
None |
1 |
A GCS score of 3, for example, is the deepest level
of unconsciousness, describing a person who is totally unresponsive
to even painful stimulation. A score of 9 or more indicates that the
person is no longer in a coma, but is not fully alert. The highest
score of 15 refers to a person who is awake, oriented and able to
obey verbal commands.
Severity of injury is typically categorized into three
levels: mild (or minor), moderate and severe. Although clinicians
and researchers have adopted a variety of definitions of these respective
categories, a commonly used rule of thumb is that minor injury refers
Moderate injuries and severe injuries are defined in terms of increasingly
lengthier durations of LOC and lower GCS's at initial medical assessment.
Typically a GCS of 9-12 defines a moderate injury and 3-8 a severe
injury.
Although initial "severity" measures may predict "severe"
long-term impairments in some individuals, initial severity scores
do not correlate one-to-one in terms of negative consequences in a
person's life. As will be discussed below, the effects of TBI on individuals
and the meaning of those effects vary with a variety of factors, only
one of which is initial "severity of injury".
However, severity is a useful concept in discussing
post-injurys recovery and treatment, as the scenario is usually quite
different for those with moderate to severe injuries versus those
with minor injuries. Discussion of the latter group will be delayed,
to allow an expanded description of the course of recovery after more
severe injuries.
