The effects of post-traumatic amnesia on information processing following mild traumatic brain injury

Primary objective: The aim of this study was to determine whether a single measurement of level of PTA could distinguish patients more severely injured from those less so, by investigating the effect of PTA on psychometric test performance. Methods and procedures: Ninety patients with mTBI completed a word recall test, a spoken version of the Speed of Comprehension test and the Digit Symbol Substitution Test (Digit Symbol), within 24 hours of injury. These patients were divided into two groups, based on the presence (n=42) or absence (n=48) of PTA at the time of testing. PTA was measured with an eight-item orientation scale. Main outcomes and results: An independent groups design showed that patients with mTBI in PTA recalled fewer words after two presentations and after a delay and completed fewer symbols in 90 seconds on Digit Symbol than patients with mTBI not in PTA. Discriminant function analysis was applied to explore whether classifying severity of injury in terms of number of orientation questions answered would be useful. Conclusions: These results indicate that for individuals with mTBI in PTA, speed of information processing and verbal memory are impaired. A single brief administration of orientation questions may be sufficient to provide an index of severity of mTBI within the first 24 hours