Title: Preliminary speech recognition results after cochlear implantation in patients with unilateral hearing loss: a case report

Transcription

1 Author's response to reviews Title: Preliminary speech recognition results after cochlear implantation in patients with unilateral hearing loss: a case report Authors: Yvonne Stelzig (yvonnestelzig@bundeswehr.org) Roland Jakob (rolandjakob@bundeswehr.org) Joachim Mueller (joachim.m@mail.uni-wuerzburg.de) Version: 3 Date: 28 January 2011 Author's response to reviews: see over

2 Dear Editor, Dear referees, We would like to thank you for your suggestions. We have implemented these and added explanations where needed. Please note that due to the word limit given by JMCR (2000 words), we were not always able to answer your questions/comments within the manuscript as explicitly as we would have liked. In these cases, we added the explicit explanation to our answers below. Even though we are aware of the word limit, we were unable to only reach the 2000 words as otherwise we would not have been able to address your suggestions satisfactorily. Yours sincerely, Yvonne Stelzig Editor: As stated earlier, authors should give a statement regarding authorization of CI in unilateral SNHL by the hospital or national health governing body We now added the following: All patients were thoroughly counselled and signed informed consent before implantation. Authorisation was provided by the Germany army as patients were treated by the Central hospital of the Federal Armed Forces in Koblenz, Germany. Authors stated that "All patients in the study were members of the German army and appeared to be highly motivated for CI treatment". Although, authors stated that cases were counselled and informed consent was obtained but this statement needs further clarification i.e. why they appeared to be highly motivated? CI cases needs counselling on pros and cons by the team of treating hospital rather than motivation by either self extracted knowlegde or by other doctor/audiologist/vender (conflict of interest). As stated in the article, patients were thoroughly counselled by medical professionals. However, personal motivation to have a cochlear implantation plays also an important role. The patients were highly motivated as they felt that their job was at risk. We now added the following Patients did not wear hearing aids (HAs) before implantation as their hearing loss (HL) was too profound for HAs to provide sufficient acoustic amplification. Since all patients were

3 members of the German army, which is obliged by law to provide the best possible compensation for any kind of disability, treatment costs were no issue. Patients, who all had leading positions within the army, consistently reported a high level of distress often related to feelings that their job was at risk because of their HL and were thus highly motivated for CI treatment. All patients were thoroughly counselled and signed informed consent before implantation. Authorisation was provided by the Germany army as patients were treated by the Central hospital of the Federal Armed Forces in Koblenz, Germany. Authors have not provided details of the hearing aid being used by the cases before CI but they stated that "Overall, patients rated the unilateral CI to be better than the BAHA head band". This statement needs clarification. CI speech is quite different, and patient needs a lot of counselling sessions before its implantation. Even if highly motivated, other digital hearing aids can provide better acceptance/results in these unilateral SNHL. Cochlear implant is costly and will render an ear dead if failed. Therefore authors should discuss these issues in the 'Discussion'. o Patients did not wear any hearing aids before implantation as their hearing loss was too profound for hearing aids to provide sufficient acoustic amplification. Thus, cochlear implantation represented the best treatment option, considering in particular that all patients wanted to keep their employment. o Since all patients were members of the German army, which is obliged by law to provide the best possible compensation for any kind of disability, treatment costs were no issue. Furthermore, all patients were profoundly deaf on the ear to be implanted. Thus, cochlear implantation - even if results were not as beneficial as expected represented a good chance of restoring hearing to a certain degree. We added the following to the methods part: Patients did not wear hearing aids (HAs) before implantation as their hearing loss (HL) was too profound for HAs to provide sufficient acoustic amplification. Since all patients were members of the German army, which is obliged by law to provide the best possible compensation for any kind of disability, treatment costs were no issue. We added the cost factor to the discussion: The patients in our present study had profound UHL for which HAs would not have rendered sufficient acoustic amplification. Since all patients were members of the German army, treatment costs were no issue; although, generally, cost-effectiveness plays an important role in health care structures. However, based on the results of studies by Bond et al. [15],

4 for example, the decision of unilateral cochlear implantation should not be influenced or even restrained by cost-related arguments. We would have like to shortly explain Bond s study as follows. We were, however, restricted by the word limit: Bond et al. [15] systematically reviewed the effectiveness and cost-effectiveness of multichannel unilateral cochlear implants for adults and found that there was evidence across studies of a consistent effect in favour of unilateral cochlear implants compared to no support or acoustic hearing aids. Previous cost-effectiveness calculations, based on UK implant centre data, show that in the UK, unilateral cochlear implantation is likely to be costeffective given current assessment and treatment processes. Based on these calculations and in particular on the fact that unilateral cochlear implantation is indeed beneficial for the patients, the decision of unilateral cochlear implantation should not be influenced or even restrained by cost-related arguments. We also added the respective reference to the Reference list: [1] Bond M, Elston J, Mealing S, Anderson R, Weiner G, Taylor R, Stein K: Systematic reviews of the effectiveness and cost-effectiveness of multi-channel unilateral cochlear implants for adults. Clin Otolaryngol 2010, 35(2): Authors reported use of VAS in the report but authors replied to the comment of the reviewer that they didn't have documentation on better localization of sound in traffic or group. This statement by the CI cases could be due to psychological effect, and hence can't be validated. CI benefit is better observed with objective tests with masking of normal hear. Since the results of the VAS were only contingently reproducible and since the VAS was unfortunately not validated, we deleted the VAS paragraph from the Methods and Results parts. However, as the positive subjective results provide important and interesting information, we added the following paragraph to the Discussion. We specifically emphasised that the subjective results might have been influenced by psychological effects and thus represent only a tendency. We are aware that the benefit of CIs can be better observed by objective tests but as studies show (e.g. Helbig et al.,2008), investigating the subjective

5 benefits may often reveal additional positive or negative aspects related to a device which might not be reflected in objective testing. We added the following. Unfortunately, we were again restricted by the word limit and thus had to rewrite this paragraph in order to be able to add the required information. To obtain a tendency of the subjective perception, we used a Visual Analogue Scale (VAS), ranging from 0 (very low) to 10 (very high). Patients stated a high level of CI acceptance, integration of CI hearing, increased ease of listening especially in noise and a regaining of acoustic orientation abilities. After patients became accustomed to the CI sound, they also rated the quality of the sound signals generated by the CI to be good. No negative interference of NH when using the CI was reported. This can probably be attributed to the advancing CI technology having developed modern coding strategies with high frequency resolution and temporal processing. Overall, the subjective ratings of the CI were more positive than results of the objective testing. It should be emphasized, however, that the VAS was not validated but shows a tendency of how the CI is perceived. It must furthermore be stated that the subjective results might possibly be influenced by psychological effects, such as the patients high motivation and expectations towards CI implantation. It might thus be interesting for future studies to focus in greater detail on the subjective benefits of unilateral CIs in particular, as well as on possible psychological effects influencing the subjective perception. This contrast between objective and subjective benefits might also be due to the fact that the speech tests are designed for bilateral HL and not for NH on the contralateral side. The results in the acoustic-only condition might be dominated by the NH ear, thus decreasing the measurable difference between acoustic-only and binaural test results. A further explanation might be that all patients reported improved sound localisation abilities, which, however, cannot be fully reflected in speech tests, even if two separately placed speech sources are used. It would be an attractive aspect for future unilateral CI studies to include localisation tests and to investigate if subjective and objective results continue to show different levels of improvement. Furthermore, future studies should include a greater subject population and adapted speech tests focusing on unilateral hearing so that statistical significance can be demonstrated.

6 Helbig S, Baumann U, Helbig M, von Malsen-Waldkirch N, Gstoettner W. A new combined speech processor for electric and acoustic stimulation--eight months experience. ORL J Otorhinolaryngol Relat Spec 2008;70(6): Referee 2: Comments to authors: I feel the authors have adequately and fairly addressed previous concerns. One further recommendation would be to clarify the use of "db" throughout the manuscript. For example, the authors do specify a difference between SPL and HL, however when using "db" it is helpful to include which scale is being referenced each time (especially since both are used in this study). For example: 35 db SPL, or 35 db HL. We now clearly defined if db HL or db SPL is referenced. (Please see yellow highlights in the manuscript).