Interpretation of Brainstem Auditory Evoked Potentials: Results from Intracranial Recordings in Humans

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Abstract
The results of recording intracranially from the auditory nerve, lower brain-stem 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 showed that the auditory nerve is the neural generator of the first 2 peaks in the human ABR [auditory brainstem response]. Recording from the entrance of the 8th nerve into the brain stem and locations close to that reveal potentials: the latencies of the peaks in these potentials match those of peaks III and IV. These peaks were assumed to have their source in 2 and 3rd-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. The neural generator of this component of the potential recorded from the inferior colliculus was the lateral lemnisculi; 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.