Cochlear implantation in adults: a systematic review and meta-analysis. 
Sensorineural hearing loss is the third leading cause of years lived with disability worldwide.  Cochlear implants may provide a viable alternative to hearing aids for this type of hearing loss.  The Coverage and Analysis Group at the Centers for Medicare & Medicaid Services was interested in an evaluation of recently published literature on this topic.  In addition, this meta-analysis is to our knowledge the first to evaluate quality-of-life (QOL) outcomes in adults with cochlear implants.  To evaluate the communication-related outcomes and health-related QOL outcomes after unilateral or bilateral cochlear implantation in adults with sensorineural hearing loss.  MEDLINE, Cochrane Central Register of Controlled Trials, Scopus, and previous reports from January 1, 2004, through May 31, 2012.  Published studies of adult patients undergoing unilateral or bilateral procedures with multichannel cochlear implants and assessments using open-set sentence tests, multisyllable word tests, or QOL measures.  Five researchers extracted information on population characteristics, outcomes of interest, and study design and assessed the studies for risk of bias.  Discrepancies were resolved by consensus.  A total of 42 studies met the inclusion criteria.  Most unilateral implant studies showed a statistically significant improvement in mean speech scores as measured by open-set sentence or multisyllable word tests; meta-analysis revealed a significant improvement in QOL after unilateral implantation.  Results from studies assessing bilateral implantation showed improvement in communication-related outcomes compared with unilateral implantation and additional improvements in sound localization compared with unilateral device use or implantation only.  Based on a few studies, the QOL outcomes varied across tests after bilateral implantation.  Unilateral cochlear implants provide improved hearing and significantly improve QOL, and improvements in sound localization are noted for bilateral implantation.  Future studies of longer duration, higher-quality reporting, and large databases or registries of patients with long-term follow-up data are needed to yield stronger evidence.