Hybrid cochlear implantation: clinical results and critical review in 13 cases.

Objective: To substantiate the benefits of hybrid cochlear implantation (CI) in patients with residual low-frequency hearing.

Study Design: Prospective study of patients in a manufacturer-sponsored clinical trial.

Setting: Independent referral center for CI.

Patients: Thirteen patients who met candidacy criteria for a hybrid CI. The 10 women and 3 men had a mean age of 51 years.

Intervention: Preoperative evaluation, CI with a Nucleus Hybrid cochlear implant, subsequent programming, and diagnostic testing.

Main Outcome Measures: Benefits of high-frequency electrical stimulation from the hybrid CI as measured by conventional audiometry, consonant-nucleus-consonant monosyllabic word and Bamford-Kowal-Bench sentence in noise testing at quarterly intervals per protocol.

Results: Follow-up ranged from 3 to 24 months. All 13 patients had preserved hearing immediately postoperative. However, one lost residual hearing 7 days postoperatively, and 2 patients had delayed hearing losses at 2 and 24 months, the latter apparently due to barotrauma; however, this was not conclusive. Another had a bilateral symmetrically progressive hearing loss. Six patients showed changes in low-frequency hearing less than 10 dB; 2 showed changes in the range 11 to 20 dB; 2, 21 to 30 dB; and 3, more than 50 dB. Eleven of 13 had improved consonant-nucleus-consonant words ranging up to 83% when tested with hearing aid + CI in the operated ear. Four subjects exhibited improvement in Bamford-Kowal-Bench sentence in noise testing, although only one subject showed a significant decline associated with bilateral progression in hearing impairment.

Conclusion: Combined electrical and acoustical hearing can result in significant improvement in speech understanding. Only one patient lost residual hearing as a direct result of surgery. Two others had delayed losses. There are no absolute predictive factors as to success with hybrid CI, just as there are none for conventional CI. Similarly, wide variation in results may occur. Further studies may clarify factors involved in such variation.