Long-latency auditory-evoked potentials in severe traumatic brain injury

Objective: To detect the effects of different deviant stimuli on long-latency auditory-evoked potentials (LLAEPs) in patients with severe impairment of consciousness from traumatic brain injury (TBI) and to define their prognostic value for late functional outcome. Design: Correlational study on a prospective cohort. Setting: Brain injury rehabilitation center, Patients: Eleven volunteers and 21 consecutively sampled patients with severe TBI referred to the inpatient intensive rehabilitation unit of primary care in a university-based system. Main Outcome Measures: The LLAEPs recorded with different paradigms; and the Glasgow Outcome Scale (GOS), Disability Rating Scale (DRS), FIM(TM) instrument, and Neurobehavioural Rating Scale (NBHRS). Results: N100-P150 complex showed high reliability. Patients with good outcomes showed N100 and P150 mean latencies similar to those of unimpaired patients and shorter than patients with unfavorable outcomes. When the deviant stimulus was the patient's name, N100 latency showed high correlations with DRS (p <.007), FIM (p <.01), and NBHRS (p <.009). P250 and P300 showed a low percentage of occurrence with passive paradigms in both patients and controls. Their scores were inversely correlated to the Glasgow Coma Scale (p <.03) and the Innsbruck Coma Scale (p <.003), but no significant correlations were found with functional and behavioral outcomes. Patients with COS score 1-2 1 year posttrauma had significantly longer latency and lower amplitude of N100 and P150 than those with GOS score 4-5. Conclusions: LLAEPs can be recorded in patients with severe impairment of consciousness by means of passive paradigms, The use of a stimulus that is relevant for the patient can enhance the accuracy of the test and its relationship with functional outcome.