Atraumaticity and Deep Insertion

Abstract

Background: An atraumatic insertion is one of the conditions to succeed to preserve low frequencies in case of electro acoustic stimulation. Preservative procedures are also important to preserve vestibular functions, particularly in very young children, and in case of bilateral implantation. Atraumaticity requires a specific surgical procedure, and a specific electrode array. Many publications reported high rates of hearing preservation with short electrodes. Nevertheless, many evidences argue for potential benefits of using cochlear implant electrodes that extend into the apical regions of the cochlea. A complete coverage provides additional low-pitched auditory percepts and thereby increases the spectral information. Apical electrodes are able to selectively stimulate discrete and tonotopically ordered neural populations near the apex of the spiral ganglion. In this area, neuronal tissue (ganglion cells) is dense. Intracochlear potentials recordings showed that this area is very reactive and clinical evaluation demonstrated patient’s preferences to complete cochlear coverage. Medel developed a long atraumatic electrode (flex soft) and the aim of this study is to evaluate the hearing preservation with this electrode and the benefit of the bimodal stimulation. Materials and methods: this multicentric study (Rennes, Bordeaux, Paris, Lyon) included 12 patients who were implanted with Medel Sonata Ti100, electrode 31,3 mm flex soft. The low frequencies were preserved in all these patients and a speech processor EAS DUET was applied for electroacoustic stimulation. Patients were tested in different situations: acoustic only, electric only, and bimodal electroacoustic. Results: There was a significant advantage for the EAS condition in speech recognition in quiet situation and in noise. Questionnaires exhibited patients’ preferences for the EAS condition. Conclusion: preservation of inner ear functions is possible with a long electrode with a specific surgical procedure and an atraumatic electrode array. Providing information from low frequencies increases auditory performances.