The Laryngoscope C 2014 The American Laryngological, V
Rhinological and Otological Society, Inc.
Choice of Ear for Cochlear Implantation: Implant the Better- or Worse-Hearing Ear? Aniruddha Patki, MD; Debara L. Tucci, MD, MS, MBA BACKGROUND The availability of cochlear implants (CIs) has led to significant advances in hearing rehabilitation. Indications for implantation have expanded significantly since the technology was introduced, and many more patients today are considered eligible for the device. As indications have become less restrictive, patients with poor but serviceable hearing in at least one ear have been implanted. In such patients, implantation of the poorer ear allows the possibility of bimodal stimulation, utilizing a contralateral hearing aid (HA). However, implantation of the poorer ear has raised concerns that the implant could be less beneficial in an auditory system that has been long deprived of stimulation. Analysis of this question may be aided by addressing two related questions: 1) Is there a clear benefit to bimodal stimulation (utilizing one HA and one CI) over stimulation with one CI alone? 2) Does the degree of hearing loss preimplant affect the derived benefit from the implant? If the answer to the first is yes and the answer to the second is no, then the ideal ear to implant should be the poorer ear.
LITERATURE REVIEW Benefit of Bimodal Stimulation Bimodal stimulation is defined as the use of electrical stimulation (CI) in one ear and acoustic stimulation delivered via a HA in the opposite ear. A 2008 systematic review of the effectiveness of bimodal stimulation reported a “moderate” strength of evidence in support.1 The potential benefit of such stimulation is that the CI gives access to high-frequency information that is important for speech perception, and the residual low frequency hearing amplified by the CI provides improved ability to hear in the presence of background noise.1 In
The authors have no funding, financial relationships, or conflicts of interest to disclose. From the Division of Otolaryngology Head and Neck Surgery, Department of Surgery, Duke University, Durham, North Carolina, U.S.A Send correspondence to Debara L. Tucci, Division of Otolaryngology, Duke University Medical Center, Durham, North Carolina. E-mail: [email protected] DOI: 10.1002/lary.24736
Laryngoscope 125: January 2015
addition, the binaural advantage conferred by bimodal stimulation may result in improved localization, and the continued stimulation of the nonimplanted ear may reduce ongoing auditory deprivation, preserving any residual auditory function.1 The authors acknowledge a lack of strong evidence to support bimodal stimulation primarily because of the fact that, although many studies on this topic have been published and all report significant (although not universal) benefit, a high level of evidence such as seen with randomized clinical trials is not observed. In 2012, Firszt et al. examined the benefit of bimodal stimulation versus CI only in a group of 10 adults with asymmetric hearing loss who received a CI in their poorer ear. The study was novel in that these subjects were not considered CI candidates by current standards because of the amount of residual hearing in the better ear; however, all met criteria for a CI in the poorer-hearing ear. All patients used a contralateral HA postimplant. Seven had postlingual hearing loss in the CI ear, whereas three had pre/perilingual onset of severe–profound hearing loss. Assessments included word and sentence recognition in quiet and noise, sentence recognition in noise (fixed and restaurant noise), localization, and hearing handicap scale. The majority (5/7) of the postlingual hearing loss subjects showed bimodal advantage over the CI-alone condition on at least one test measure.2 Benefit was less clear in this study for those with pre/perilingual hearing loss in the CI ear, only one of whom had open set speech understanding. Postlingually deafened subjects demonstrated improved localization with bimodal input, and all subjects showed decreased mean hearing handicap ratings postimplant, indicating a perceived benefit in everyday life.2
Preimplant Hearing Status as a Predictor of Performance Post-CI Gantz et al. in 2002 studied 10 adult patients who underwent bilateral cochlear implantation in order to evaluate, in an intrasubject design, the relationship between preimplant physiologic measures and postoperative hearing outcomes. The authors found no correlation between pre-implant electrophysiologic measures and speech perception testing measured at 3 and 12 months postimplant.3 In fact, by 12 months post-CI, there was no relationship between any preoperative measure and Patki and Tucci: Ear Choice in Cochlear Implantation
5
speech performance. The authors speculated that good word understanding provided through one CI could stimulate central mechanisms and in this manner facilitate auditory processing through the other poorer ear.3 Francis and colleagues in 2005 investigated the relationship between residual hearing in the implanted ear and speech perception post-CI. The authors used a retrospective design to examine hearing performance in 86 unilaterally implanted patients who were divided into three groups: bilateral severe hearing loss, bilateral profound loss, and asymmetrical severe–profound (severe in one ear, profound in the other); groups were matched for other factors such as duration of deafness that are thought to impact CI performance. By 1 year postimplant, there was no difference in performance of an implanted ear with profound hearing loss in the asymmetric group versus the bilateral severe group.4 However, performance following unilateral implantation in the bilaterally profound hearing loss group was poorer than performance in a group that had severe hearing loss in at least one ear.4 As with prior studies,3 the authors suggest that it is the status of the hearing/nonhearing brain that impacts post-CI results more than the hearing status of the implanted ear. The presence of residual hearing in at least one ear provides persistent auditory stimulation that appears to confer benefit to even a profoundly impaired ear with CI stimulation.3,4 In a large retrospective international study of 2,251 postlingually impaired CI recipients, Lazard and colleagues examined the relationship between pre-, peri-, and postoperative factors and postoperative performance. The authors found that implanting the better or worse ear had no effect on performance, confirming their impression that implantation of the poorer hearing ear
Laryngoscope 125: January 2015
6
is unlikely to reduce CI outcome.5 Similar to prior studies,4 the level of residual hearing in the better ear had significant positive influence on CI outcome. Again, results confirm the importance of central auditory function in post-CI patient performance.
BEST PRACTICE These studies demonstrate significant benefit of bimodal stimulation over a single CI. Furthermore, the benefit of a CI to speech perception appears to be more positively correlated with the integrity of central nervous system pathways for auditory processing than the preimplant functional status of the inner ear and eighth cranial nerve. This suggests that in patients with asymmetric hearing loss, in cases where a single ear is to be implanted, the optimal choice of ear for cochlear implantation is the poorer ear.
LEVEL OF EVIDENCE This work cites 1 level 2a, 2 level 2b, and 2 level 2c publications.
BIBLIOGRAPHY 1. Olson AD, Shinn DB. A systematic review to determine the effectiveness of using amplification in conjunction with cochlear implantation. J Am Acad Audiol 2008;19:657–671. 2. Firszt JB, Holden LK, Reeder RM, Cowdrey L, King S. Cochlear implantation in adults with asymmetric hearing loss. Ear Hear 2012;33:521–533. 3. Gantz BJ, Tyler RS, Rubinstein JT, et al. Binaural cochlear implants placed during the same operation. Otol Neurotol 2002;23:169–180. 4. Francis HW, Yeagle JD, Bowditch S, Niparko JK. Cochlear implant outcome is not influenced by the choice of ear. Ear Hear 2005;26:7S–16S. 5. Lazard DS, Vincent C, Venail F, et al. Pre-, per- and postoperative factors affecting performance of postlingually deaf adults using cochlear implants: a new conceptual model over time. PLoS One 2012;7:e48739.
Patki and Tucci: Ear Choice in Cochlear Implantation
Rhinological and Otological Society, Inc.
Choice of Ear for Cochlear Implantation: Implant the Better- or Worse-Hearing Ear? Aniruddha Patki, MD; Debara L. Tucci, MD, MS, MBA BACKGROUND The availability of cochlear implants (CIs) has led to significant advances in hearing rehabilitation. Indications for implantation have expanded significantly since the technology was introduced, and many more patients today are considered eligible for the device. As indications have become less restrictive, patients with poor but serviceable hearing in at least one ear have been implanted. In such patients, implantation of the poorer ear allows the possibility of bimodal stimulation, utilizing a contralateral hearing aid (HA). However, implantation of the poorer ear has raised concerns that the implant could be less beneficial in an auditory system that has been long deprived of stimulation. Analysis of this question may be aided by addressing two related questions: 1) Is there a clear benefit to bimodal stimulation (utilizing one HA and one CI) over stimulation with one CI alone? 2) Does the degree of hearing loss preimplant affect the derived benefit from the implant? If the answer to the first is yes and the answer to the second is no, then the ideal ear to implant should be the poorer ear.
LITERATURE REVIEW Benefit of Bimodal Stimulation Bimodal stimulation is defined as the use of electrical stimulation (CI) in one ear and acoustic stimulation delivered via a HA in the opposite ear. A 2008 systematic review of the effectiveness of bimodal stimulation reported a “moderate” strength of evidence in support.1 The potential benefit of such stimulation is that the CI gives access to high-frequency information that is important for speech perception, and the residual low frequency hearing amplified by the CI provides improved ability to hear in the presence of background noise.1 In
The authors have no funding, financial relationships, or conflicts of interest to disclose. From the Division of Otolaryngology Head and Neck Surgery, Department of Surgery, Duke University, Durham, North Carolina, U.S.A Send correspondence to Debara L. Tucci, Division of Otolaryngology, Duke University Medical Center, Durham, North Carolina. E-mail: [email protected] DOI: 10.1002/lary.24736
Laryngoscope 125: January 2015
addition, the binaural advantage conferred by bimodal stimulation may result in improved localization, and the continued stimulation of the nonimplanted ear may reduce ongoing auditory deprivation, preserving any residual auditory function.1 The authors acknowledge a lack of strong evidence to support bimodal stimulation primarily because of the fact that, although many studies on this topic have been published and all report significant (although not universal) benefit, a high level of evidence such as seen with randomized clinical trials is not observed. In 2012, Firszt et al. examined the benefit of bimodal stimulation versus CI only in a group of 10 adults with asymmetric hearing loss who received a CI in their poorer ear. The study was novel in that these subjects were not considered CI candidates by current standards because of the amount of residual hearing in the better ear; however, all met criteria for a CI in the poorer-hearing ear. All patients used a contralateral HA postimplant. Seven had postlingual hearing loss in the CI ear, whereas three had pre/perilingual onset of severe–profound hearing loss. Assessments included word and sentence recognition in quiet and noise, sentence recognition in noise (fixed and restaurant noise), localization, and hearing handicap scale. The majority (5/7) of the postlingual hearing loss subjects showed bimodal advantage over the CI-alone condition on at least one test measure.2 Benefit was less clear in this study for those with pre/perilingual hearing loss in the CI ear, only one of whom had open set speech understanding. Postlingually deafened subjects demonstrated improved localization with bimodal input, and all subjects showed decreased mean hearing handicap ratings postimplant, indicating a perceived benefit in everyday life.2
Preimplant Hearing Status as a Predictor of Performance Post-CI Gantz et al. in 2002 studied 10 adult patients who underwent bilateral cochlear implantation in order to evaluate, in an intrasubject design, the relationship between preimplant physiologic measures and postoperative hearing outcomes. The authors found no correlation between pre-implant electrophysiologic measures and speech perception testing measured at 3 and 12 months postimplant.3 In fact, by 12 months post-CI, there was no relationship between any preoperative measure and Patki and Tucci: Ear Choice in Cochlear Implantation
5
speech performance. The authors speculated that good word understanding provided through one CI could stimulate central mechanisms and in this manner facilitate auditory processing through the other poorer ear.3 Francis and colleagues in 2005 investigated the relationship between residual hearing in the implanted ear and speech perception post-CI. The authors used a retrospective design to examine hearing performance in 86 unilaterally implanted patients who were divided into three groups: bilateral severe hearing loss, bilateral profound loss, and asymmetrical severe–profound (severe in one ear, profound in the other); groups were matched for other factors such as duration of deafness that are thought to impact CI performance. By 1 year postimplant, there was no difference in performance of an implanted ear with profound hearing loss in the asymmetric group versus the bilateral severe group.4 However, performance following unilateral implantation in the bilaterally profound hearing loss group was poorer than performance in a group that had severe hearing loss in at least one ear.4 As with prior studies,3 the authors suggest that it is the status of the hearing/nonhearing brain that impacts post-CI results more than the hearing status of the implanted ear. The presence of residual hearing in at least one ear provides persistent auditory stimulation that appears to confer benefit to even a profoundly impaired ear with CI stimulation.3,4 In a large retrospective international study of 2,251 postlingually impaired CI recipients, Lazard and colleagues examined the relationship between pre-, peri-, and postoperative factors and postoperative performance. The authors found that implanting the better or worse ear had no effect on performance, confirming their impression that implantation of the poorer hearing ear
Laryngoscope 125: January 2015
6
is unlikely to reduce CI outcome.5 Similar to prior studies,4 the level of residual hearing in the better ear had significant positive influence on CI outcome. Again, results confirm the importance of central auditory function in post-CI patient performance.
BEST PRACTICE These studies demonstrate significant benefit of bimodal stimulation over a single CI. Furthermore, the benefit of a CI to speech perception appears to be more positively correlated with the integrity of central nervous system pathways for auditory processing than the preimplant functional status of the inner ear and eighth cranial nerve. This suggests that in patients with asymmetric hearing loss, in cases where a single ear is to be implanted, the optimal choice of ear for cochlear implantation is the poorer ear.
LEVEL OF EVIDENCE This work cites 1 level 2a, 2 level 2b, and 2 level 2c publications.
BIBLIOGRAPHY 1. Olson AD, Shinn DB. A systematic review to determine the effectiveness of using amplification in conjunction with cochlear implantation. J Am Acad Audiol 2008;19:657–671. 2. Firszt JB, Holden LK, Reeder RM, Cowdrey L, King S. Cochlear implantation in adults with asymmetric hearing loss. Ear Hear 2012;33:521–533. 3. Gantz BJ, Tyler RS, Rubinstein JT, et al. Binaural cochlear implants placed during the same operation. Otol Neurotol 2002;23:169–180. 4. Francis HW, Yeagle JD, Bowditch S, Niparko JK. Cochlear implant outcome is not influenced by the choice of ear. Ear Hear 2005;26:7S–16S. 5. Lazard DS, Vincent C, Venail F, et al. Pre-, per- and postoperative factors affecting performance of postlingually deaf adults using cochlear implants: a new conceptual model over time. PLoS One 2012;7:e48739.
Patki and Tucci: Ear Choice in Cochlear Implantation
