Three frequency component waveforms of auditory evoked brainstem response in spinocerebellar degeneration.

Under adequate stimulus intensities, the power spectra of normal auditory evoked brainstem responses (ABRs) are composed of three major components: 0-350 Hz, 350-700 Hz and 700-1200 Hz. By means of a digital filter using fast Fourier transform, three ABR waveforms consisting of each frequency component of the power spectrum were obtained. The significance of these three component waveforms in the analysis of ABR abnormality was estimated in 30 patients with spinocerebellar degeneration (SCD). In conventional wave latency analysis, 9 out of 30 patients (30%) had abnormal ABRs, the main abnormality being prolonged interpeak latencies of waves I-III, I-V and the disappearance of wave V. On the other hand, component waveforms were abnormal in 82.5% of the cases. These results suggest that analysis of ABRs by the use of component waveforms is useful for detecting abnormality in the brainstem auditory pathway in SCD patients.