Localizing and prognostic value of auditory evoked responses in coma after closed head injury

We studied brainstem auditory evoked responses (BAERs) in 26 comatose patients after head injury, and long-latency auditory evoked responses (AERs) in 24 patients. BAERs-AERs were graded for abnormality to evaluate graded outcome. Only six patients had central BAER abnormalities. AERs were abnormal in 21, and all patients with abnormal BAER had abnormal AER, implying that the major site of injury affected the cerebral hemispheres. BAER was abnormal in only 5 of 12 with decerebration, suggesting that decerebration may occur with diffuse hemispheric injury. BAER (p less than 0.01) and AER (p less than 0.01) strongly correlated with outcome. Preservation of AER and normal BAER indicated good quality of survival; absent AER and normal BAER, survival; and absent AER and abnormal BAER, severe disability or death. BAER-AER predicted outcome as accurately as the detailed neurologic examination and occasionally added predictive power.