Analysis of P1 Latency in Normal Hearing and Profound Sensorineural Hearing Loss

OBJECTIVES P1 is a robust positivity at a latency of 50-150 msec in the auditory evoked potential of young children. It has been reported that over the first 2-3 years of life, there is a rapid decrease of the latency and the mean P1 latency in adults with normal hearing is approximately 60 msec. This study was designed to evaluate the change of the P1 latency in Koreans with normal hearing according to age and to compare this with the P1 latency of young patients with profound sensorineural hearing loss before and/or after cochlear implantation. METHODS Among the patients who visited the Department of Otorhinolaryngology at Seoul National University Hospital from June 2007 to September 2009, the P1 response was recorded in 53 patients in the normal hearing group, in 13 patients in the pre-cochlear implantation (CI) group and in 10 patients in the post-CI group. A synthesized consonant-vowel syllable /ba/ was used to elicit the evoked responses. The evoked responses were collected using the center of the frontal head. For each subject, an individual grand average waveform was computed by averaging the ten recordings. The P1 latency was visually identified as a robust positivity in the waveform. RESULTS For the normal hearing group, the P1 latency showed the pattern of shortening as the age increased (coefficient, -0.758; P<0.001). For the pre-CI group, 10 cases showed delayed latencies and 3 cases did not show the P1 wave. For the post-CI group, the P1 latencies showed a less delayed tendency than those of the pre-CI group, but this was not statistically different. CONCLUSION This report provides the standard value of the P1 latency at each age in Koreans for the first time and the findings support that the maturation of the central auditory pathways could be measured objectively using the P1 latency.