[Effect of REZ-I cochlear implantation on residual hearing in adult patients]

To evaluate the effect of cochlear implantation with REZ-I straight electrodes on residual hearing of postlingually deafened adults, and to explore the audiologically safety and injury characteristics of cochlear implantation.

Sixteen unilateral REZ-I (22 channels) cochlear implantation recipients from September 2009 to December 2009 were picked out. Their pre-and post-implantation audiometry data including pure-tone audiometry (PTA), auditory steady-state responses (ASSR), auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE) were retrospectively analyzed, in order to compare the change between pre- and post-implantation residual hearing.

Among the 12 recipients who had some measurable residual hearing before implantation, 5 (41.6%) patients had conserved some measurable hearing but the other 7 (58.4%) recipients had lost all measurable hearing after implantation on the implanted side. The implanted ears had an average PTA threshold drop of 9.5 dB HL and a statistically significant difference between pre- and post-implantation (P < 0.05) PTA thresholds in the frequencies of 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz. Compared to non-implanted ears, the drop in 500 Hz and 1kHz had a statistically significant difference between pre- and post-implantation PTA thresholds (P < 0.05). The ASSR residual hearing threshold elevation were statistically significant (P < 0.05) between pre- and post-implantation ASSR at 250 Hz and 500 Hz on the implanted side, while the The ASSR residual hearing threshold elevation were statistically significant (P < 0.05) at 500 Hz when compared to non-implanted side. The difference of residual hearing between pre- and post-implantation was not statistically significant for both DPOAE and ABR.

There will be a certain degree of damage to residual hearing of the implanted side following REZ-I cochlear implantation.