The study will follow a cohort of CI-candidates becoming CI-user, till two years postoperative. A through-out assessment of both their audiological and vestibular status will be carried out at multiple fixed timepoints over 2 years, evaluating both subjective (patients reported) and objective outcomes over time. For the audiological part of the study both pure-tone and speech audiometry results will be held against the patient perceived benefit of the treatment as assessed by the questionnaires NCIQ and SSQ-12. The vestibular part of the study will evaluate the function of the SCCs and the sacculus. This is will be put in concert with functional tests of the vestibular system, and the patient perceived outcome measure DHI. Correlations between vestibular and audiological performances will be examined. A collection of specific hypotheses will be tested by predefined statistical methods.

Inclusion Criteria:

• Adults (At or above 18 years of age and capable of giving an informed consent)
• Cochlear implant candidacy
• Profound bilateral post-lingual hearing loss
• Proficiency in Danish
• Expected ability to participate on both all pre- and postoperative examinations
• No previous CI experiences

Exclusion Criteria:

• Later abandonment of CI candidacy
• Blindness or visual handicap compromising eye movement evaluation
• Distinct neck mobility handicap hindering either vHIT- or cVEMP examination
• Patient reluctance, such as consistent no-show or cancellations of appointments
• CI-surgery before preoperative evaluation could be obtained
• Simultaneous bilateral cochlea implantation.
• Sequential CI within the follow-up period

Adult CI-candidates are to be included from our tertiary referral centre at the Audiological Department at Aalborg University Hospital, Aalborg, Denmark.

Full plan of analysis and raw data will be presented given there is still anonymity for the participants.