[Negative potential auditory brainstem response with 3-msec latency in profoundly deaf patients: characteristics and relationship to vestibular evoked response].

A large negative deflection with a latency of 3 msec was observed in the auditory brainstem response (ABR) waveforms of 48 patients (6.5%), [59 ears (5.8%)] in 740 patients with profound peripheral deafness (1,009 ears) between 1978 and 1990 at our department. This negative deflection was termed the "N3 potential." We reviewed some of these patients and discuss some common characteristics found in abnormal ABR waveforms. We also inquired into the conditions and origins of these potentials. Although virtually all patients were less than 10 years of age, the N3 potential was also observed in the ABR waveform of adult patients. There were no sex differences. In the majority of patients audiograms showed no response to the maximum output of an andiometer in the high frequency range and a residual response in the low frequency range. The most common cause of deafness was "unknown" in children, and "sudden deafness" in adults. The N3 potentials were noted at intensities of 80 dBnHL or greater. A high repetition rate (83.3/sec) of the click stimulus influenced the latency and amplitude of the N3 potential. As the stimulus intensity increased, the amplitude of the potential increased, and the latency decreased. The potential was replicated on retesting within less than a month. The N3 potential had a consistent latency and amplitude over the scalp. We conclude that the N3 potential was a physiological "neural" response evoked by a loud sound rather than by an electrical artifact. The N3 potential was most likely not an auditory evoked response or a response from a semicircular canal, because of the 3-msec latency and sharpness of the waveform, with lack of vertigo. The results suggest that the N3 potential may be a saccular acoustic response.