Hearing Conservation Surgery Using the Hybrid-L Electrode

Patients with high-frequency deafness and/or substantial residual hearing across frequencies might benefit from combined electro-acoustic stimulation. The Hybrid-L electrode was designed to address the issues of both hearing conservation and effective electrical stimulation in those recipients. The electrode with 22 contacts should be inserted through the round window membrane, and covers approximately 270 degrees of the basal turn of the cochlear. This insertion length is equivalent to the one seen in many patients using the former Nucleus straight electrode. Twenty-four patients with low-frequency thresholds of 60 dB or better, up to 500 Hz, were implanted with a Hybrid-L device in a clinical trial at the Medical University of Hannover. Another group of 8 recipients with less residual hearing was included under extended inclusion criteria. Residual hearing was conserved in the majority of cases. One patient had a loss of more than 30 dB, but hearing partially recovered after 9 months. The median loss in all patients was 10 dB in both the Hybrid group and the extended group. Patients were able to use the residual hearing postoperatively to the same extent as preoperatively. In the Hybrid mode (cochlear implant + ipsilateral hearing aid), patients showed a significant improvement of 21% (p = 0.002) in speech understanding in quiet using the Freiburger Monosyllabic Word Test compared to the preoperative scores under aided conditions with their hearing aid. The Oldenburg Sentence Test in noise showed a remarkable average improvement of 10.2 dB (p < 0.001) compared to the preoperative hearing aid only mode. An additional improvement could be seen in the combined mode using an additional contralateral hearing aid. Recipients with a shorter duration of high-frequency hearing loss showed a larger benefit than those with a longer duration of hearing loss. Hearing conservation using the Hybrid-L electrode and a given surgical technique is possible with high probability in patients with high-frequency deafness or pantonal hearing loss. The use of the residual acoustic hearing offers specific advantages, especially for understanding speech in noise and for spatial hearing.