Auditory brainstem responses in Rett syndrome: effects of hyperventilation, seizures, and tympanometric variables

This study examined the effects of tympanometric variables, stage of disease, hyperventilation, and seizures on the auditory brainstem response (ABR) in Rett syndrome (RS). Thirty-four female children with RS ranging in age from 2 years, 3 months to 15 years, 7 months participated in the study. ABRs and tympanograms were recorded from all of the subjects. When the ABR peaks were identifiable, interpeak latency intervals (IPLIs) for I-III, III-V, and I-V were computed for each waveform. The peaks (I, III, and V) and IPLIs were characterized as abnormal if either the peaks were absent or the latencies were greater than 2 SD from the normative data (obtained on female children). Analyses revealed significant prolongation of wave I latencies in Rett children with abnormal tympanograms. ABR wave III latencies were significantly affected by the presence of seizures and hyperventilation. The Pearson chi-square statistic revealed significant differences in the rate of wave III and V abnormalities due to the presence and degree of hyperventilation and the presence of seizures. Wave I abnormalities were also observed in the presence of normal middle ear function, suggesting the presence of sensorineural hearing impairment in some RS children. Clinical implications of these findings are discussed.