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Gulf War and Health, Volume 7: Long-Term Consequences of Traumatic Brain Injury
It was originally intended that the GCS would be applied repeatedly during a patient’s hospital course to monitor improvement or deterioration—during emergency transport, in the emergency department (ED), during intensive care, and throughout primary care. Because GCS scores have been reported in almost all recent studies of TBI severity, it is important to compare only readings taken at similar times after injury among studies. The most common time for determining the GCS score is 6 hours after injury, which is generally when the patient is in the ED. The GCS is subject to limitations when used on some patients, such as young children, people with extensive facial injuries that would preclude eye assessment, people subject to cross-language misunderstandings, and people who have been intubated or sedated on arrival at the ED. A major limitation of the GCS is the effect of intoxication. As many as 35–50% of adult civilian patients transported to the ED may be under the influence of alcohol (Jagger et al., 1984a), so its effect on the GCS score and its interpretation cannot be ignored. A study by Sperry et al. (2006), however, suggests that alcohol intoxication had little effect on the GCS.
Nell and associates (2000) introduced an extended version of the GCS (GCS-E) to address difficulties of its application to the mild forms of TBI (Table 3.1). A study by Drake and colleagues (2006) showed that the extended GCS is a useful tool for the prediction of symptoms connected with mild TBI. The GCS should not be confused with the Glasgow Outcome Scale (GOS) (Table 3.1). The GCS is a physiologic measure of consciousness and the GOS is a gross measure of complications or residual effects following severe brain injury (Jennett and Bond, 1975).
Other methods and instruments have been used as alternatives to the GCS, such as the Abbreviated Injury Scale (AIS) (see Chapter 2) and the International Classification of Diseases (ICD). Clinical measures—such as loss of consciousness (LOC) and duration of posttraumatic amnesia (PTA)—and computed tomography of brain lesions have also been used to assess TBI severity. Table 3.2 shows examples of TBI incidence studies conducted in the United States that used those measures. As can be seen there is no consistency in severity classification systems reflecting available clinical symptoms or evidence from neuroimaging. A review of popular injury scales can be found in the review by MacKenzie (1984).
Outcome Scores and Predictors
The literature is replete with attempts to predict TBI outcomes on the basis of measurements in the ED or soon after intensive care. One of the most commonly used measures is the GOS (Table 3.1) developed by Jennett and Bond (1975). Although the intent of the GOS was to address severe TBI, it has been applied over the years to less severe TBI. It is acknowledged as a crude measure of medical (neurologic) complications and sequelae but has found favor as a quick and reliable indicator of outcome especially of severe TBI (Teasdale et al., 1998). The GOS is most commonly applied at 3, 6, or 12 months postinjury but can be used at any time after intensive care. Pettigrew and associates (2003) recently showed that the GOS can be successfully applied over the telephone. There are many other measures, but only the GOS is covered in this chapter to assess patient disposition at hospital discharge. Because the gross categories of the GOS have some limitations, an extended version (the GOS-E) was developed (Jennett et al., 1981); the GOS-E adds three categories to the GOS and has good inter-rater agreement.