Effects of maternal preeclampsia on brain-stem auditory evoked response in very low birth weight infants.

OBJECTIVE: Because stress in utero may enhance neuromotor maturation, we hypothesized that infants born to mothers with preeclampsia would have a shorter absolute latency V and interpeak latency I-V period (brain-stem conduction time) of brain-stem auditory evoked response (BAER) than infants born to normotensive mothers. STUDY DESIGN: A retrospective cohort study was performed to assess the effects of maternal preeclampsia on BAER of very low birth weight infants. The cohort consisted of 24 infants with a birth weight less than 1251 gm born to mothers with preeclampsia, and 48 infants born to normotensive mothers, matched for birth date within 2 months, gestational age, and chronologic age at the time of the BAER test. The BAER test was completed before discharge, with the infant in a quiet state and the use of a 30 dB stimulus. RESULTS: The mean latencies of wave V were shortened bilaterally (left 8.60 +/- 0.6 msec vs 9.02 +/- 0.6 msec, p < 0.008; right 8.61 +/- 0.6 msec vs 8.96 +/- 0.6 msec, p < 0.033, and the interpeak latency of I-V was significantly shortened compared with the control subjects on the left (left 4.91 +/- 0.5 msec vs 5.38 +/- 0.6 msec, p < 0.003; right 5.17 +/- 0.5 msec vs 5.37 +/- 0.6 msec, not significant). CONCLUSION: These results suggest that the intrauterine stress of maternal preeclampsia accelerates the maturation of the auditory nerve and brain-stem auditory pathway in very low birth weight infants.

Some forms of tinnitus may involve the extralemniscal auditory pathway.

It has previously been shown that the click-evoked responses recorded from the intracranial portion of the eighth nerve in patients with incapacitating tinnitus are not abnormal, nor is the latency of peak III of the click-evoked brainstem auditory-evoked potentials significantly altered; however, the latency of peak V is slightly (but significantly) shortened in comparison to that of patients with the same degree of hearing loss but no tinnitus. In this study the hypothesis that the extralemniscal auditory system is involved in the generation of tinnitus is tested. We made use of the fact that neurons of the extralemniscal auditory system also receive input from the somatosensory system, and that stimulation of the somatosensory system can influence the processing of auditory information in the extralemniscal system. In 4 of 26 patients with mild-to-severe tinnitus whose median nerve was stimulated electrically, the tinnitus increased noticeably during stimulation, in 6 the intensity of the tinnitus decreased noticeably, and in the remaining 16 there was no noticeable change in the tinnitus. In some of the patients the character of the tinnitus changed in a complex way. There were no significant differences in hearing thresholds in these three groups of patients. Electrical stimulation of the median nerve in 12 individuals with normal hearing who did not have tinnitus either had no effect on the loudness of sounds or it caused a slight increase in the loudness.

Correlative changes of auditory nerve and microphonic potentials throughout sleep.

Gross cochlear potentials in response to alternating clicks and pure tone bursts were recorded in guinea-pigs with chronically implanted electrodes in the round window during sleep and the awake state. A significant increase in both averaged potentials, the compound auditory nerve action potential (cAP) and cochlear microphonics (CM) occurred in slow wave sleep (SWS) with a subsequent diminution in paradoxical sleep (PS) periods. The cAP, CM, amplitude and area averages were similar during quiet wakefulness and in PS. Moreover, as an episode of PS progressed, the recorded potentials continued to decrease. On the other hand, increased averaged values were again observed during a subsequent episode of SWS. An involvement of the efferent olivo-cochlear bundle is postulated, first, because it is the only known pathway connecting the CNS and the auditory periphery and, second, because several key pre-receptor variables (middle ear muscles and ossicles and sound-source ear relation) were either abolished or altered dramatically.

Brainstem auditory evoked response (BAER): Clinical perspectives and normative data.

Research pertaining to the physiological mechanisms involved in the generation of brainstem auditory evoked responses is reviewed emphasizing the current status of its clinical applications, pointing out present gaps in knowledge and delineating avenues for further inquiry. Some work conducted in our laboratory aimed at statistical description of BAER parameters relevant to clinical practice is presented, along with assessment procedures that are deemed promising for routine work. Relevant implementation procedures are described.