Comparison of indices of traumatic brain injury severity: Glasgow Coma Scale, length of coma and post-traumatic amnesia

Background: Classification of traumatic brain injury (TBI) severity guides management and contributes to determination of prognosis. Common indicators of TBI severity include Glasgow Coma Scale (GCS) scores, length of coma (LOC) and duration of post-traumatic amnesia (PTA). Objective: To compare GCS, LOC and PTA by examining distributions and intercorrelations and develop multivariable linear regression models for estimating LOC and PTA duration. Methods: Prospective study of 519 of 614 consecutive patients with TBI. Indices of TBI severity studied were GCS, LOC, PTA and PTA-LOC (the interval from return of command-following to return of orientation). Candidate predictor variables for estimation of LOC, PTA and PTA LOC intervals were age, years of education, year of injury (before 1997 vs 1997 or later), GCS, LOC (for PTA and PTA-LOC), pupillary responsiveness, type of injury, CT pathology and intracranial operations. Results: Although there was a severity/response relationship between GCS and LOC, PTA and PTA-LOC intervals, there was overlap in these intervals between GCS severity categories. Age, year of injury, GCS, pupillary responsiveness and CT pathology were predictive of LOC. Age, years of education, year of injury, GCS, LOC, pupillary responsiveness and intracranial operations were predictive of PTA duration. Age, years of education, year of injury, GCS, LOC and pupillary responsiveness were predictive of PTA-LOC. GCS and LOC effects were influenced by age. Conclusions: Predictors for estimating LOC, PTA and PTA-LOC intervals were determined and simple equations were developed. These equations will be helpful to clinicians, researchers and those counselling family members of patients with TBI.