This study will test an experimental Tinnitus Implant System that consists of a cochlear implant, sound processor and programming software. The Tinnitus implant is surgically placed under the skin just behind the ear in the mastoid bone. It has an electrode that extends from the implant into the promontory bone of the cochlea which emits electrical signals that stimulate the auditory nerve. The sound processor is worn behind the ear and powers the implant via the coil. The study will be conducted in adults with moderate to severe chronic tinnitus who have normal hearing to moderately severe hearing loss in the inner ear. The study participants will undergo a series of tests that include evaluations of tinnitus loudness and annoyance, and self-reported questionnaires on their tinnitus and general health.

Inclusion criteria

• 18 years or older.
• Normal hearing to moderately severe sensorineural hearing loss defined as a pure tone average (PTA) at 500, 1000, 2000 and 4000 Hz less than 65 dB HL in both ears (separately) and best-aided phoneme recognition score more than or equal to 80% in both ears (separately).
• Unilateral or asymmetric subjective (no pulsatile) tinnitus. In case of asymmetric tinnitus, the worst ear must be implanted.
• Tinnitus duration of at least 6 months.
• Severe tinnitus loudness determined by a. VAS-L score in the severe range i.e. 50-100/100 b. TFI score in the severe range i.e. 52-90/100
• Tinnitus that is intractable and has not been ameliorated satisfactorily by standard of care such as CBT or hearing aid, when such interventions are potentially clinically indicated.
• Clinically significant reduction in VAS-L score (≥ 15/100 points) in response to trans-tympanic promontory stimulation
• Willing and able to provide written informed consent.
• Medically able to use the device and to undergo general anaesthesia for implantation taking into account their medical condition, contraindications and surgical risks.
• Dutch language proficiency

Exclusion Criteria:

• Pulsatile tinnitus.
• Any anatomical or structural abnormalities of the inner ear, cochlear nerve, or brainstem that would negatively impact response to study intervention (determined in a temporal bone CT and if necessary (e.g. possibility of vestibular/acoustic schwannoma) by a MRI scan of the head (of sufficient quality at the discretion of the investigator) not more than five years old at the time of enrolment
• Medical contraindications limiting correct placement, activation, or treatment (determined by medical history; contraindications include brain or major ear surgery, brain or temporal bone tumor(s), recurrent ear infections within the last year, otosclerosis, prior major head trauma that results in sudden injury that causes damage to the brain and results in lasting cognitive impairment).
• Any medical condition, including mental illness or substance abuse, deemed by the Investigator to likely interfere with a patient's ability to sign informed consent, cooperate and/or participate in the study, or interfere with the interpretation of the results (incl. pregnant or breastfeeding women or patients with unrealistic expectations).
• Presence of clinically diagnosed depression or anxiety determined by a psychological state evaluation (if PHQ-9 > 9 or GAD-7 > 9).
• Active (currently or within two months prior to enrolment) use of medications (taking regularly scheduled antidepressant, anxiolytic, antipsychotic or antiepileptic medications, or other neuromodulator agents) or other tinnitus treatments.
• It is permissible to include people who use such medications at lower doses as a sleep aid or for people who intermittently use such medications for situational anxiety (e.g., Ativan before airplane travel). A change in medication during the trial should be avoided.
• It is permissible to include people who prefer to use a hearing aid to amplify ipsilateral hearing loss. The start of using a hearing aid during the trial should be avoided.
• Investigator site personnel directly affiliated with this study and/or their immediate families; immediate family is defined as a spouse, parent, child, or sibling.
• Cochlear employees or employees of Contract Research Organizations or contractors engaged by Cochlear for the purposes of this investigation.
• Current participation, or participation in another interventional clinical study/trial in the past 60 days, involving an investigational drug or device (unless the other investigation was/is a Cochlear sponsored investigation and determined by the investigator or Sponsor to not impact this investigation).