MED-EL Cochlear Implants (CI) provide auditory sensations via electrical stimulation of the auditory pathways for severely to profoundly hearing-impaired individuals who obtain little or no benefit from acoustic amplification in the best aided condition.

However, there is only few evidence from large long-term observational studies available to gain knowledge on clinical effectiveness of cochlear implants. With continued pressure on healthcare system budgets, there is an increasing demand for evidence-based research that demonstrates an intervention is effective in the real-world environment across large and diverse populations. Currently, there is a paucity of data concerning the long-term outcomes of subjects implanted with a SONATA 2 cochlear implant from representative samples of the population. This retrospective study aims at analyzing SONATA 2 cochlear implant data from clinical routine.

Data from SONATA 2 CI recipients will be transferred to predefined fields in an electronic data capture system (CASTOR EDC) by the investigators. The data transfer starts after the approval of the Ethics Committees (EC). Data will be included for all subjects who meet the inclusion/exclusion criteria

Inclusion Criteria:

• At least one MED-EL SONATA 2 cochlear implant with a compatible MED-EL audio processor

Exclusion Criteria:

• Lack of compliance with any inclusion criteria

In this retrospective observational study, the inclusion and exclusion criteria encompass all individuals with a SONATA 2 cochlear implant at the study centers. By including all individuals with a SONATA 2 cochlear implant from the study centers, the investigation population is representative of the target population. The investigation population is representative of "real-world" users of SONATA 2 cochlear implant.