Recent studies have reported successful reduction of tinnitus after cochlear implantation (CI) in most CI users, but the mechanisms of reduction and the amount of improvement is not fully understood. Especially, the relative role of peripheral and central auditory pathways is not clearly known. This study assessed the effect of CI electrical stimulation on tinnitus in subjects with unilateral tinnitus related to a single-sided deafness (SSD), and relative contributions of peripheral and central auditory pathways in tinnitus reduction.

Introduction: Continuous surgical, technological and audiological advances are responsible for the ever improvement of outcomes obtained through cochlear implants (CI) over the last decades. These positive observations have progressively led to the cautious extension of CI indications including patients with single-sided deafness (SSD). SSD patients are characterized by the loss of functional hearing in one ear, causing an impairment of binaural hearing abilities, with important difficulties for sound localization and speech in noise comprehension. These patients also often present invalidating tinnitus in the deaf ear, worsening both their psychological and audiological conditions. Recent studies have reported successful reduction of tinnitus intensity after cochlear implantation. However, most studies included a very limited number of participants and tinnitus evaluation tools. The impact of CI speech perception abilities in SSD is still under debate.

Objective: This study aims to assess the effect of CI electrical stimulation on tinnitus, speech-in-noise and speech-in-quiet abilities in a group of 30 SSD patients.

Methods: After cochlear implantation, patients are stimulated using continuous white noise stimulation in the first month period and thereafter using a conventional stimulation. This was done to investigate the effects of non-meaningful, and therefore only peripheral, stimulation. Outcomes were monitored at 1, 3, 6 and 12 months of CI use. Tinnitus loudness and annoyance were measured with a Visual Analog Scale and tinnitus distress and quality of life were evaluated with tinnitus questionnaires (THI, TRQ and STSS). Speech in noise comprehension was assessed in three different spatial listening configurations and speech in quiet was evaluated through direct connection with the speech processor.

Inclusion Criteria:

• Age over 18
• Profound to total single sided deafness with associated tinnitus
• Normal or near-normal hearing on contralateral ear
• Tinnitus evaluated by THI ≥ 58 and VAS on annoyance ≥8
• Failure of usual tinnitus treatments
• Duration of tinnitus between 1 and 15 years
• Normal vestibular function of contralateral ear
• Native of fluent French speaker

Exclusion Criteria:

• No Social security affiliation
• Retrocochlear pathology (vestibular schwannoma, severe central auditory processing disorder)
• Cochlear ossification
• Middle ear pathology
• Tinnitus not related to deafness
• Depression with BDI (Beck Depression Inventory) > 16 or unfavorable advice from psychologist/ psychiatrist