Tinnitus and cochlear implantation: impact and outcomes

Abstract

Unilateral cochlear implantation (UCI) is the standard treatment for adult patients with bilateral severe to profound sensorineural hearing loss (SNHL). A symptom often prevalent in patients with severe to profound SNHL is subjective tinnitus. In the first part of this thesis, the effect of cochlear implantation on tinnitus is investigated with multiple study designs and in different patient groups. A systematic review of the literature showed a decrease of tinnitus severity after UCI on group level. On patient level, however, increase of tinnitus and newly induced tinnitus were also reported in a minority of patients. The results we found with our retrospective cohort study, evaluating the 10-year results of a tertiary center, were in line with the results of the systematic review. Which patients with preoperative tinnitus will recover from tinnitus after cochlear implantation and which patients not, is barely investigated. For that reason, we performed a retrospective study developing and internally validating a multivariable prediction model for tinnitus recovery following UCI. Three significant predictors for tinnitus recovery after UCI were found: a lower preoperative score on a speech perception test (Consonant-Vowel-Consonant test), unilateral localization of tinnitus and a larger deterioration of residual hearing at 250 Hz. The performance of this first prediction model is promising, however, a larger prospective study is needed before it can be used in daily clinical practice. Candidacy for cochlear implantation has changed through the years. The last decades there is a growing interest in bilateral cochlear implantation (BiCI) in patients with bilateral severe to profound SNHL. Contrary to UCI, only a few studies reported on the effect of BiCI on tinnitus, with contrary results. Therefore, we studied the effect of simultaneous and sequential BiCI on tinnitus. These results were comparable to the tinnitus results after UCI. There is an ongoing global discussion on whether or not BiCI should be standard clinical care for adult patients with bilateral severe to profound SNHL. One major point of this discussion, is the cost-effectiveness. An often-used method to evaluate cost-effectiveness is a cost-utility analysis. In these analyses, the outcomes of self-reported quality of life instruments, in particular health utility instruments, are leading. We found incomparable results between different general health utility instruments, used in cochlear implant studies. This is problematic as the choice of instrument will largely affect the outcome: cost-effectiveness. This thesis also showed that most general health utility instruments are not appropriate to measure changes after cochlear implantation. The more disease-specific quality of hearing questionnaires are more appropriate to measure subjective changes after cochlear implantation. Although there is a growing interest in the use of subjective outcome measures in the current healthcare system, these instruments are hardly used in the current clinical evaluation of cochlear implantation. This thesis underlines the importance and necessity of subjective outcome measures in the evaluation of cochlear implantation, as current objective tests do not fully reflect subjective everyday listening situations.