A prospective cohort study of cochlear implantation as a treatment for tinnitus in post-lingually deafened individuals

Introduction

As the most successful neural prosthesis, cochlear implants have restored functional hearing to one million individuals¹. About half of the users are prelingually deafened children with most being able to develop normal language, while the other half are post-lingually deafened adults who can carry on a conversation on the phone^2,3. Despite this success, treating hearing loss has remained the only approved indication for cochlear implantation since 1984.

Hearing loss is associated with many other ear disorders like tinnitus, which is the perception of sound that does not have an external source⁴. Tinnitus is present in about 80% of those with hearing loss and 10-20% of the general population^{5, 6–7}. Tinnitus is a nuisance to some but debilitating to many, affecting focus and sleep, and leading to anxiety, depression and even suicide. Current standard care relies on behavioral therapies that relieve tinnitus symptoms, but do not cure tinnitus⁸.

Historically, clinicians have noted that the cochlear implant could suppress tinnitus^9,10. Further case studies identified electrical stimulation parameters for tinnitus suppression^{11, 12–13} and several clinical trials demonstrated promising results including treating incapacitating unilateral tinnitus in patients with single-sided deafness^{14, 15, 16, 17–18}. A 2021 review identified 10 studies with only 89 patients using intracochlear electrical stimulation to relieve tinnitus¹⁹. Despite the lack of a pre-defined protocol that resulted in >50% missing data, a large retrospective study of 300 patients also found a beneficial effect of the cochlear implant on alleviating tinnitus and distress²⁰. A more recent prospective study involving 72 patients who responded to questionnaire showed that 58% of them complained about tinnitus before implantation and 60% of those with pre-implantation tinnitus experienced a clinically signification reduction 3 months post-implantation²¹. However, these studies have not provided sufficient evidence to make cochlear implantation a labeled indication for the treatment of tinnitus²². Additionally, reports on cochlear implantation inducing or worsening tinnitus have introduced outcome uncertainty and heightened the potential risk of implantation^{23, 24–25}.

Here we designed a prospective two-year cohort study to examine the efficacy and risk of cochlear implantation on tinnitus and related symptoms in 323 post-lingually deafened individuals (>16 years old), including those with...