Evoked Auditory Brainstem Responses In Pre-Term Neonates

Computer averaging can be used in recording low amplitude, far-field reflections of electrical activity in stimulated auditory pathways ascending the brainstem in man. These evoked responses were recorded from pre-term neonates in the Neonatal Intensive Care Unit at Orange County Medical Center. Recordings were made while the infants were in environmentally-regulated isolettes with the use of conventional EEG electrodes. Clicks at 65, 45, and 25 dB SL (re: normal hearing adults) were applied via a headphone. Seven components were found within the first 15 msec following stimulation. Latency (msec) and amplitude (nanovolts) were measured and compiled with the individual infant's estimated gestational age. Results from clinically normal and abnormal patients were grouped separately, and brainstem pathology reports were evaluated on patients which expired. Responses from normal subjects decreased in latency with maturation. Amplitudes and latencies in abnormal patients deviated from the established normal pattern. Auditory evoked responses are quantitative measures which can be useful in estimating gestational age and hearing integrity, and determining the neurological status of brainstem structures in the auditory pathway.