As previously noted, one of the scales used to assess early outcome after hospitalization for TBI is the GOS. The GOS is a crude indicator of medical (neurologic) complications or of residual effects at the time of discharge from a primary treatment center. The major difficulty with the GOS is its inability to classify patients properly because of the lack of specific criteria that separate severe from moderate and moderate from the good-recovery categories. Good recovery does not mean, nor was it ever intended to mean, complete recovery, and, as noted above, Jennett and Teasdale (1981) devised an extended version of the GOS (GOS-E) to account for the insensitivity of the scale to some changes in functional ability, especially in the moderate and severe categories.
The large number of population-based TBI incidence studies might suggest the availability of much more information on the GOS as an early hospital-discharge tool, but only seven of the 66 studies (US and non-US) reported on the scale. Rimel (1981) observed that 69% of TBI patients had a “good recovery” at the time of discharge. The highest percentage of persistent vegetative state was also reported in that study. Almost all other studies in Table 3.15 had a rate of good recovery of 75% or higher. The one exception is the study by Masson et al. (2003), in which only 18% of patients were discharged with a good recovery; their study population, however, consisted of only patients admitted to the hospital with severe TBI.
Almost all the incidence studies had shortcomings, and that should be considered in drawing conclusions. No two published studies are identical in methods. However, many studies have used reasonable methods to identify patient cases, defined and measured the populations that gave rise to the patients, used acceptable methods in identifying patients in treatment facilities or in administrative datasets, defined TBI (and severity levels) in reasonable ways, classified exposures that gave rise to the injuries in ways that make sense, recorded basic descriptive information about patients in uniform formats, and, in longitudinal studies, followed patients for outcomes by using acceptable methods to reduce losses and used accepted outcome instruments. Thus, we can learn a great deal about the epidemiology of TBI and use that knowledge to help in designing prevention strategies.