A multicentre study on the clinical utility of post-traumatic amnesia duration in predicting global outcome after moderate-severe traumatic brain injury.
BACKGROUND
Past research shows that post-traumatic amnesia (PTA) duration is a particularly robust traumatic brain injury (TBI) outcome predictor, but low specificity limits its clinical utility.


OBJECTIVES
The current study assessed the relationship between PTA duration and probability thresholds for Glasgow Outcome Scale (GOS) levels.


METHODS
Data were prospectively collected in this multicentre observational study. The cohort was a consecutive sample of rehabilitation patients enrolled in the National Institute on Disability and Rehabilitation Research funded TBI Model Systems (n = 1332) that had documented finite PTA duration greater than 24 h, and 1-year and 2-year GOS.


RESULTS
The cohort had proportionally more Good Recovery (44% vs 39%) and less Severe Disability (19% vs 23%) at year 2 than at year 1. Longer PTA resulted in an incremental decline in probability of Good Recovery and a corresponding increase in probability of Severe Disability. When PTA ended within 4 weeks, Severe Disability was unlikely (<15% chance) at year 1, and Good Recovery was the most likely GOS at year 2. When PTA lasted beyond 8 weeks, Good Recovery was highly unlikely (<10% chance) at year 1, and Severe Disability was equal to or more likely than Moderate Disability at year 2.


CONCLUSIONS
Two PTA durations, 4 weeks and 8 weeks, emerged as particularly salient GOS probability thresholds that may aid prognostication after TBI.