Conductive hearing loss during infancy: effects on later auditory brain stem electrophysiology

Long-term effects on auditory electrophysiology from early fluctuating hearing loss were studied in 27 children, aged 5 to 7 years, who had been evaluated originally in infancy. For controls (Group A), infant auditory brain stem responses (ABRs) were normal from birth to age 2 years. A second group (Group B) had intermittent conductive hearing loss. A third group (Group C) had more abnormal ABRs during infancy than Group B and more severe and frequent conductive hearing loss. For this follow-up study, all children had normal peripheral hearing at test. ABRs were obtained to monaural and binaural stimuli. Binaural interaction (BI) in the ABR was assessed in difference traces, derived by subtracting summed binaural from summed monaural waveforms. Controls differed from both groups with early hearing loss for wave III and wave V latencies and interpeak I-III and I-V latencies. There was a significant difference in the presence of BI. Eight of 9 A subjects and 8 of 9 B subjects, but only 4 of 9 C subjects, had demonstrable BI. Findings suggest that early fluctuating hearing loss disrupts later auditory brain stem electrophysiology.