Audiometric tests
CM
Intraoperative setting. Center of the intraoperative setting is the digital microscope. During electrode insertion, residual hearing is monitored by ECochG potentials measured as Cochlear microphonics which are transferred via a video converter from a laptop to the digital microscope and visualized in the top right corner in the surgeon’s field of view. Patients´ CT scans are displayed in the top left corner. Postoperative control for correct intracochlear positioning of the electrode is performed with C-arm X-ray-unit (left side)The acoustic component of the sound processor was connected to a disposal sound tube (for 3 M E-A-RTONE™ insert earphones, 3 M AEARO) and a disposal ear-tip (3 M E-A-RLINK™, 3 M AEARO). The ear tip was positioned in the ear canal before surgery started. ECochG potentials were acoustically generated with a tone burst of 250 Hz, 112 dB HL and a duration of 7 ms. The screen of the Cochlear™ Research Platform 1.1 was transferred to the digital microscope ARRISCOPEPreoperatively, all patients underwent standard tone and speech audiometry as well as objective hearing tests like auditory brainstem response (ABR) and cochlear microphonics (CM) in routine cochlear implant screening by professional audiometrists using Auritec audiometer (Auritec GmbH, Hamburg, Germany) and BERA Eclipse EP 25/ECochG/ASSR (Interacoustics A/S, Assens, Denmark). Additionally, air and bone conduction were measured one day before and one day after surgery. Postoperative monitoring of residual hearing and speech perception was performed at 6 weeks, 3 months, 6 months and 12 months postoperatively. All tests were performed according to the declaration of Helsinki and were approved by the local ethics committee. Informed written consent was obtained from all patients.