Auditory short, middle, and long latency responses in acutely comatose patients.

For assessing comatose patients, the combination of auditory short, middle, and long latency evoked potentials (auditory brain stem response [ABR], middle latency component [MLC], and slow vertex response [SVR] ) is more comprehensive than auditory brain stem response (ABR) only or ABR with slow vertex response (SVR). Fifty-four acutely comatose patients were studied. Thirty-four of the patients had severe head injury and others had coma of varied etiology. Within two months after admission, 25 patients survived, while 29 patients died. Auditory evoked response measurements were conducted usually within 48 to 72 hours after admission. For patients with normal SVR, MLC, and ABR, there was 100% survival; with absent SVR but normal MLC and ABR, survival was 91%; with absent SVR and MLC and normal ABR, it was 60%; with abnormal ABR, it was 10%; no patient survived whose ABR was absent. It is emphasized that a normal MLC is clearly a predictor of survival of comatose patients, but a normal ABR is not always a reliable indicator of survival.