First Combined Auditory Brainstem and Cochlear Implantation (ABCI) Using a Double Array Device

Introduction: Today in some cases of NF2 (after tumor removal), auditory neuropathy, and auditory nerve hypoplasia, it cannot be predicted with absolute certainty which implant, a CI or an ABI, will give the best postoperative functional outcome. Indeed, no test is available by which one may verify the function of the remaining auditory nerves fibers. Therefore, we have applied the new concept of a dual implantation of an ABI and a CI, called ABCI.

Material and Methods: A double-array device was custom-made by the Cochlear Company for this application. A Nucleus 24 implant was equipped with a split electrode presenting a 90-mm Hybrid-L electrode for the cochlea and a 115-mm lead as the ABI electrode. Ten channels were assigned to the CI and another 10 channels to the ABI.

Results: The first patient received an implant of this device in November 2008. He presented with a 1-cm IC growing vestibular schwannoma and bilateral profound sensorineural hearing loss with ongoing degradation. Via an extended translabyrinthine approach, the tumor was removed, with anatomical preservation of the cochlear nerve, and the ABI electrode was inserted in the lateral recess of the 4th ventricle. Then the cochlear electrode was inserted. At the third fitting after 2 months, CI stimulation to thresholds around 40 dB was achieved, and the first auditory sensations were induced by brainstem stimulation. The 6-month functional results will be presented.

Conclusion: In light of the preliminary results in a first case, the authors believe that the concept of this dual implantation ABCI might be promising in selected cases. This could be helpful in NF2 patients with still small tumors where auditory fibers can be preserved during tumor removal. Its use could also be extended to nontumor indications (VIII hypoplasia, neuropathy, cochlear otosclerosis). The simultaneous electrode insertion would avoid patient disappointment, unnecessary reoperations, and morbidity. It would also allow new pathways of stimulation (cross-electrode stimulation).