The auditory brainstem evoked response in comatose children

Predicting outcome in deeply comatose children is often difficult. The clinical examination and ancillary tests, such as EEG and CT scan, fail to define accurately the etiology of coma and predict survival. Many studies have shown that the auditory brainstem evoked response (ABR) is an important diagnostic test in various neurologic diseases. The ABR is also effective in localizing brainstem lesions, defining brain death and predicting outcome. One of its major advantages is that it is relatively insensitive to changes in homeostasis and to CNS depressant drugs, so it is especially useful in patients who present in deep coma since they often exhibit marked deviations from homeostasis and receive drugs such as barbiturates and anticonvulsants to reduce increased intractanial pressure and for 'brain protection.' We report results of ABR examinations in 53 deeply comatose children varying in age from 1 day to 13 years. The primary disease was CNS infection in 26 (49.1%), head trauma in 21 (28.3%) and cerebral ischemia in 12 (22.6%). All of 22 (41.3%) with normal ABR recordings, signifying intact brainstem function, regained consciousness and were long term survivors. All of 15 (28.3%) with complete absence of ABR waves (but with sparing of wave one in some patients), signifying severe brainstem function, died. In 16 (30.2%) patients with partial absence of ABR waves and/or prolonged brainstem transmission time, the outcome was variable; seven regained consciousness and survived, five remained vegetative and four died. Partial absence of waves enabled accurate localization of brainstem lesions. This study demonstrates the efficacy of ABR as a diagnostic tool in various neurologic disease. Its relative simplicity, high validity and insensitivity to changes in homeostasis and to CNS depressant drugs make it especially important for prognosis in deeply comatose children.