Interpretation of brainstem auditory evoked potentials: results from intracranial recordings in humans

The results of recording intracranially from the auditory nerve, lower brainstem nuclei, and the inferior colliculus in more than 40 patients operated upon for hemifacial spasm and trigeminal neuralgia are presented. Recordings from the auditory nerve have shown that the auditory nerve is the neural generator of the first two peaks in the human ABR. Recordings from the entrance of the eighth nerve into the brainstem and locations close to that reveal potentials; the latencies of the peaks in these potentials match those of peaks III and IV. These peaks are therefore assumed to have their source in second-and third-order neurons of the ascending auditory pathway. Recordings from the inferior colliculus show a surface-positive deflection followed by a slow negative wave usually with several undulations. The latency of the positive peak matches that of wave V of the scalp-recorded ABR. It is assumed that the neural generator of this component of the potential recorded from the inferior colliculus is the lateral lemniscus and that the slow, surface-negative potential originates in the inferior colliculus. The latency of this slow potential is too long to explain that nucleus as the neural generator of peak V, as was assumed previously.