The preservation of residual hearing has become a high priority in cochlear implant surgery. This study was designed to substantiate whether conservation of residual hearing can be preserved after cochlear implantation using the suprameatal approach.
Retrospective chart review.
Retrospective chart review was performed in 109 severely to profoundly hearing impaired cochlear recipients who had some measurable hearing preoperatively. Subsequently, the pre- and postoperative pure-tone thresholds were analyzed by three different analyses to observe the degree of hearing preservation.
Single-subject results showed a complete conservation of residual hearing (change in pure-tone average [ΔPTA] ≤ 10 dB) in 27 of 109 patients (24.7%). Partial conservation of residual hearing (ΔPTA > 10 dB) was observed in 77 patients (70.6%), but these percentages have been affected severely by ceiling effects. Furthermore, group-subject results demonstrated that the median postoperative PTA was 11.7 dB worse than the preoperative PTA. For individual frequencies, the median deteriorations were 15, 20, 10, and 5 dB at 250, 500, 1,000, and 2,000 Hz, respectively. Stratification for the absence of postoperative hearing thresholds showed a conservation of measurable postoperative hearing levels in 17.4% of all study patients.
The results of this study demonstrate that complete preservation of residual hearing is possible in a limited number of patients using the suprameatal approach technique for cochlear implantation. For a reliable analysis of the audiometric effects of cochlear implant surgery, it is important to take into account the ceiling effects, therefore using different calculation methods to estimate the accurate deterioration of hearing thresholds.