P1 cortical auditory evoked potential in children with unilateral or bilateral cochlear implants; implication for the timing of second cochlear implantation

Objective To examine maturation of the central auditory pathway, using P1 cortical auditory evoked potential (CAEP), in
children who had received unilateral or bilateral cochlear implantation (CI).
Study design Prospective study.
Setting Tertiary referral hospital.
Methods Twenty children who had received CI due to congenital, or prelingual, deafness participated in the study. Participants
had received the 1st implant at a mean age of 3.4 ± 0.7 years; 16 had also received a 2nd CI for the contralateral ear, at
a mean age of 11.1 ± 2.1 years. P1 CAEP was recorded while using the 1st implant and, for those who received contralateral
CI, within 2 weeks of switching on the 2nd implant. Relations between P1 latency and duration with the 1st implant, and
between age at 1st CI and P1 latency, were investigated. Relations between P1 latency with the 1st and 2nd implants, and
between the interstage interval and difference between P1 latencies with the 1st and 2nd implants, were also examined.
Results P1 CAEP with the 1st implant was present in 16 of the 20 children. Mean P1 latency was shorter in the early CI
group compared with the late CI group, but this difference was not statistically significant (p = 0.154). There was a significant
negative correlation between the duration with the 1st implant and P1 latency (r = − 0.783, p < 0.001). Among the 16
children with sequential bilateral CI, P1 CAEP with the 2nd implant was present in 10. There was a significant negative
correlation between the duration with the 1st implant before receiving the 2nd implant and P1 latency with the 2nd implant
(r = − 0.710, p = 0.021); there was also a significant positive correlation between P1 latency with the 1st and 2nd implants
(r = 0.722, p = 0.018). There was not a significant correlation between interstage interval and the difference between the two
P1 latencies (r = − 0.430, p = 0.248).
Conclusion Longer cochlear implant use is associated with shorter P1 latency. Unilateral hearing with the 1st implant may
positively affect P1 latency with the 2nd CI ear. These findings imply that increased auditory experience may influence central
auditory pathway maturation and that the degree of central auditory pathway maturation before the 2nd CI, rather than the
timing when the surgery is received, may influence 2nd CI outcome in children with sequential bilateral cochlear implants.