[Direct acoustic cochlear stimulation for therapy of severe to profound mixed hearing loss: Codacs™ Direct Acoustic Cochlear Implant System].

OBJECTIVE: Implantable hearing aids have become a valid option for the therapy of various forms of hearing loss. The Codacs™ Direct Acoustic Cochlear Implant System is the first vibratory implant available for patients with severe to profound mixed hearing loss (MHL). By directly coupling sound energy into the perilymph, a very high maximum power output (MPO) is achieved over a broad frequency range. Via a conventional stapedotomy, the vibratory energy of the electromagnetic actuator is transferred directly to the perilymph through the oval window.

PATIENTS AND METHODS: This article describes the technical principle, basic surgical aspects and audiological outcomes of two clinical studies. Additional coupling procedures and extensions to the spectrum of indications are also discussed. Surgically, the two-component system can either be implanted via a purely transmastoid approach with posterior tympanotomy, or additionally via transmeatal access to the stapes footplate. Pre- and postoperative audiological results of patients wearing conventional hearing aids and with severe to profound MHL, who were implanted with the Codacs™ system at the Medical University Hannover, were compared.

RESULTS: Significant improvements over conventional hearing aids could be achieved with initial bone conduction thresholds between 44 and 63 dB HL (Ø 54 dB HL) and an air-bone gap between 19 and 51 dB HL (Ø 34 dB HL) in patients with MHL caused by advanced otosclerosis or tympanosclerosis and an intact posterior wall of the auditory canal. The mean functional gain was 50 ± 9 dB (0.5-4 kHz) and the monosyllabic word score was 85% at 65 dB presentation level compared to conventional hearingaids with 25%. Speech intelligibility in noise (S0N0) improved by 7.1 to Ø 0.3 dB SNR with Codacs™. The mean bone conduction threshold remained unchanged or showed a minimal increase in the low-frequency range.

CONCLUSION: The CODACS system provides an effective new treatment for patients with severe to profound MHL for the first time.