Cortical evoked auditory potentials with cochlear implant and in childeren

Cortical evoked auditory potentials (CEAP) are the late latency auditory responses recorded between 50 and 300 ms. P1 latency decreases by age and latency of this potential may serve as a good indicator of the central auditory development in hearing impaired children. It was shown that there is a correlation between P1 latency and duration of hearing loss. Auditory cortex remains maximally plasticity until approximately age 3-3.5 years. The aim of this study was to compare the P1 latencies in congenitally deaf children fitted with unilateral cochlear implant and age-matched normal hearing peers. This retrospective study included 40 children who underwent unilateral cochlear implantation between 2006 and 2012 and 30 normal hearing, age-matched children. Data were collected from medical and audiologic records and included the age and gender of the patient, age at device fitting, duration of device use, and P1 latencies. All of the children in cochlear implant group had congenital profound sensorineural hearing loss assessed by auditory brain stem response testing. Acoustic immitance and distortion product otoacoustic emission tests were in normal hearing children. CEAPs were measured through the Fonix® HEARLab System. Three speech sound stimuli / m /, / g /, and / t / that represent speech in the low, mid, and high frequencies presented to the patient in the free field at a level of 55 dB SPL. HEARLab System performed statistical analysis automatically and calculated a p value for each speech sound stimuli to determine whether a CAEP was actually present. Cochlear implant group included 23 (57.5%) female and 17 (42.5%) male patients with a mean age of 53.15 months (range 21-82 months). Normal hearing group comprised 17 (56.6%) female and 13 (43.3%) male patients with a mean age of 53.15 months (range 15- 84 month). A Pearson?s correlation was used to assess the correlation between the age and P1 latencies within two groups. A negative and poor correlation was found between P1(m), P1 (g) and P1(t) latencies and age in normal hearing group ( r= -0.4429). There was a negative and poor correlation between P1 latencies and duration of device use in cochlear implant group [P1(m)-r=-0.3668, P1(g)-r=-0.4887, P1(t)-r= -0.4261 ). This study showed that P1 latencies in low, mid, and high frequencies shortened as the duration of the device use increased in cochlear implant group. P1 latencies in low, mid, and high frequencies also shortened as the age increased in normal hearing group. CEAPs particularly P1 latency may be used to assess the maturation of the auditory pathways in children scheduled to receive a cochlear implant and in children fitted with cochlear implant. Key words: Cochlear implants, Cortical auditory potentials, P1 latency