Otology & Neurotology 35:e256Ye269 Ó 2014, Otology & Neurotology, Inc.

Hearing Preservation Surgery for Cochlear Implantation: A Meta-analysis *Peter Luke Santa Maria, †‡Michael Brian Gluth, §Yongqing Yuan, ‡kMarcus David Atlas, and *Nikolas H. Blevins *Department of Otolaryngology, Head and Neck Surgery, Stanford University Hospital and Clinics, Stanford, California; and ÞSection of OtolaryngologyYHead and Neck Surgery, University of Chicago Medical Center, Chicago, Illinois, U.S.A.; þEar Sciences Centre, School of Surgery, The University of Western Australia, Perth, Western Australia, Australia; §Department of Statistics, Stanford University, Stanford, California, U.S.A.; and kEar Science Institute Australia, Perth, Western Australia, Australia

Objective: To examine the results of hearing preservation in cochlear implantation surgery to identify surgical technical factors, electrode array design factors, and steroid usage, which predicts greater low-frequency hearing preservation. Data sources: A thorough search of Medline and Pubmed of English studies from January 1, 1995, to January 1, 2013, was performed using the key words ‘‘electric and acoustic hearing’’ or ‘‘hybrid cochlear implant’’ or ‘‘EAS cochlear implant’’ or ‘‘partial deafness cochlear implant’’ or ‘‘bimodal hearing cochlear implant’’ or ‘‘hearing preservation cochlear implant.’’ Study selection: The meta-analysis was conducted according to the PRISMA statement. Only articles in English were included. Studies were included if hearing preservation was the primary end point. A final number of 24 studies met the inclusion criteria. Data extraction: Patient populations were analyzed as intention to treat. Data were extracted from raw audiograms where pos-

sible. Data were excluded if not all explanatory variables were present or if variable values were ambiguous. Data synthesis: The weighted least-squares regression method was used to determine the predictive power of each explanatory variable across all studies. Conclusion: In this meta-analysis, the following are associated with better hearing preservation: cochleostomy over the round window approach, posterior tympanotomy over the suprameatal approach, a slow electrode array insertion technique over insertion of less than 30 seconds, a soft tissue cochleostomy seal over a fibrin glue only seal and the use of postoperative systemic steroids. Longer electrode arrays, topical steroid use, and lubricant use for electrode array insertion did not give an advantage. Key Words: ElectroacousticVHearing preservationVCochlear implantV Bimodal hearing. Otol Neurotol 35:e256Ye269, 2014.

Soon after it was found that partial hearing preservation (HP) was possible with standard cochlear implantation surgery (1), the concept of bimodal acoustic and electrical stimulation was introduced (2). Low-frequency HP in cochlear implantation allows the patient to take advantage of acoustic stimulation of the low frequencies with electrical stimulation of the higher frequencies. Electroacoustic stimulation (EAS) has reported benefits over electric only cochlear implantation particularly in music with pitch discrimination (3), interval perception (4), song recognition (5), and benefits in overall quality of life (6). As the concept of EAS has developed, there have been a number of

different techniques and implant designs specifically aimed at low-frequency HP (7,8) techniques have been the source of controversy and the nature of the interventions make many of them unsuitable for a randomized control trial. Outside of the very large implant centers, the number of patients who fit the criteria for hearing preservation surgery in cochlear implantation is small, leading to low-powered studies. There is a need to combine the data from multiple centers so that the evidence base for the outcomes of these techniques is stronger. The objective of this meta-analysis is to examine the results of HP in cochlear implantation surgery to identify surgical technical factors, electrode array design factors, and steroid usage, which predicts improved low-frequency HP.

Address correspondence and reprint requests to Peter Luke Santa Maria, M.B.B.S., Ph.D., Department of Otolaryngology, Head and Neck Surgery, Stanford University Hospital and Clinics, 801 Welch Rd, Stanford, CA 94305, U.S.A.; E-mail: [email protected] The authors disclose no conflicts of interest. This work was supported by the Garnett Passe and Rodney Williams Memorial Foundation. Supplemental digital content is available in the text.

MATERIALS AND METHODS Data Sources A thorough search of Medline and Pubmed was performed using the key words ‘‘electric and acoustic hearing’’ or ‘‘hybrid

e256

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HEARING PRESERVATION COCHLEAR IMPLANTATION cochlear implant’’ or ‘‘EAS cochlear implant’’ or ‘‘partial deafness cochlear implant’’ or ‘‘bimodal hearing cochlear implant’’ or ‘‘hearing preservation cochlear implant.’’ The review included the date range from January 1, 1995, to January 1, 2013. Only articles in English were included.

Study Selection The meta-analysis was conducted according to the PRISMA statement (9) (see Figure 1). A total of 1,233 possible articles were identified using the search phrases above. Only articles in English were included. During the time of the review, the authors’ own series was in the press, and the data were combined with the published literature. This study has now been published (10). Individual study bias was examined using the appraisal method at an in-study level. We recognize that each study has a bias in the selection of the inclusion criteria for patients. As there are no standards in inclusion criteria, no studies were rejected on this basis. All included studies involved surgery performed by the same unit so assume that the techniques between patients were standardized. There was no method of detecting the variability between patients in technique within these studies. Studies were excluded if HP was not a primary end point and was simply observed as an outcome retrospectively after surgery. That is, if HP was not the aim of the study, it was excluded. Forty-six individual studies were identified. Studies were then chosen based on whether the results could be interpreted or extrapolated to determine the degrees of HP according to the selected definitions. There were instances of the same study population reported by the same authors to different journals. The duplicates were not included in the review. There were also cases where authors excluded those that lost hearing from their reporting. These studies were also excluded. A final number of 24 studies met the criteria for inclusion. Data were collected into a data collection form with the variables either as yes /no or a value for continuous data. In the cases where the studies had used different techniques (such as two different TABLE 1.

e257

electrode arrays or a mixture of some adult and some pediatric patients), the data were compiled as if two or more (depending on the number of variations in technique) separate studies were done. If the study contained a mix of that variable (e.g., an age range of both adults and pediatrics) and the variable could not be defined for each patient, the variable was coded as missing and excluded from analysis of that variable. Data from each study were extracted on at least two separate occasions and cross checked to confirm that there were no differences to minimize the errors in data extraction. The following variables were examined: primary author, Pubmed ID, year of publication, number of patients, adult (Q16 yr) or pediatric (G16 yr), mean follow-up time, company of electrode array, brand of electrode array, straight or contoured electrode array, and the length of electrode array. For this analysis, the depth of insertion was assumed to be the recommended length of insertion for a particular electrode array unless, in the study methods, the depth of insertion was specifically recorded as less than the length of full insertion of the electrode array. We assumed that all patients had full insertion unless otherwise specified. When not mentioned, manufacturer device information was consulted to determine the length of insertion for a particular array. Cochleostomy and round window approaches were compared. Cochleostomy was defined as any drilling to expose the scala for insertion. This includes the extended round window approach where the scala is exposed immediately adjacent to the round window. A round window approach included any technique of drilling the round window niche but not that where the scala was exposed. Most studies simply reported either cochleostomy or round window approach. From reading studies of techniques published by the same authors, it could be guessed as to what their specific technique was but without confirmation directly from the authors, we did not want to subcategorize cochleostomy into pure cochleostomy or extended round window approaches. Also recorded were posterior tympanotomy or suprameatal approach, insertion speed as normal (not listed), slow (30 s) or long (930 s), as well as the number of seconds for insertion if listed. Also

Studies included in the meta-analysis

Primary author

Year

n

Mean hearing loss

Definition 1

Definition 2

Definition 3 G12 months

Definition 3 912 months

Arnoldner (35) Berrettini (36) Brown (14) Bruce (37) Erixon (38) Fraysse (39) Gantz (13) Garcia-Ibanez (40) Gstoettner (41) Gstoettner (42) Gstoettner (43) Helbig (44) James (45) James (46) Kiefer (47) Kuthubutheen (48) Punte (49) Radeloff (50) Santa Maria (10) Skarzycski (51) Skarzycski (52) Skarzycski (53) Tamir (54) Usami (23) Total (n)

2011 2008 2010 2011 2012 2006 2009 2009 2009 2004 2006 2011 2005 2006 2004 2012 2010 2012 2013 2010 2010 2007 2012 2011

5 30 31 14 20 27 68 28 9 21 23 18 12 10 14 5 2 2 14 95 25 10 19 5 507

Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes 488

Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes No No Yes No Yes 350

Yes No No Yes Yes No No Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes No No Yes No Yes 194

Yes No Yes Yes Yes No No Yes Yes No No No Yes Yes Yes No No Yes Yes No No Yes No Yes 143

Yes No Yes No No No No No No Yes Yes No No No No Yes Yes No Yes No No No No Yes 106

Shows a list of included studies and whether the study was included in Definitions 1, 2, and 3. Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

e258

P. L. SANTA MARIA ET AL.

collected was the use of lubricant, how the cochleostomy was sealed (soft tissue or fibrin glue), and the use of steroids as intraoperative intravenous, intraoperative transtympanic, intraoperative topical, and postoperative oral. The dose and type of steroid were also recorded. The number of patients that fell into each category of hearing preservation was recorded according to the definitions described below. There is much debate in the literature as to what defines HP and what defines low-frequency hearing. Because of this debate, we are unable to a single definition for this meta-analysis. The following definitions were found to be the most consistent. The studies used in the analysis are presented in Table 1.

Definition 1 (19 Studies, 350 Patients) Using a pure-tone average (PTA) of 250, 500, 750, and 1,000 Hz HP was defined as: Complete = postoperative PTA was within 10 dB of the preoperative PTA Partial = postoperative PTA between 10 and 20 dB of the preoperative PTA Unsuccessful = postoperative PTA was more than 20 dB compared with the preoperative PTA Nineteen of 24 studies contained results that could be interpreted according to this definition. Three hundred fifty of a total of 507 patients were included within this definition. The mean change in PTA using this definition was also collected.

forty-three of a total of 507 patients were included within this definition. After 12 months, eight of 24 studies contained results that could be interpreted according to this definition. One hundred six of a total of 507 patients were included within this definition. Studies where individual audiograms were not published, and a specific definition was used, were only included in that single definition (Definition 1, 2, or 3). If a study published the audiograms, the results were able to be extracted using more than one definition, allowing some studies to be included according to multiple definitions.

Data Extraction Patient populations within studies were analyzed as intention to treat. If the studies contained raw audiograms, the data were extracted and recorded according to the above definitions. Some studies did not report raw audiograms and only recorded results according the definitions above. Such studies could only be used under that particular definition, and the data could not be extrapolated to another definition. To allow for statistical comparison, a ‘‘no response’’ on the audiogram was recorded as 120 dB. The limits of the audiometer may be different between institutions and for different frequencies; however, these data could not be extracted from the various studies and, therefore, an assumption was made to standardize the limit at 120 dB. Data were excluded if not all explanatory variables were present. Data were also discarded if variable values were ambiguous. For example, if a study did not report the age of patients, they were excluded from the analysis examining age as a variable.

Definition 2 (16 Studies, 194 Patients) This is similar to the definition above except that the PTA was calculated using 250, 500, 1,000, and 2,000 Hz. HP was defined as: Complete = postoperative PTA was within 10 dB of the preoperative PTA Partial = postoperative PTA between 10 and 20 dB of the preoperative PTA Unsuccessful = postoperative PTA was more than 20 dB compared with the preoperative PTA The difference between Definitions 1 and 2 is the inclusion of 2,000 Hz and the exclusion of 750 Hz. Sixteen of 24 studies contained results that could be interpreted according to this definition. One hundred ninety-four of a total of 507 patients were included within this definition. The mean change in PTA using this definition was also collected.

Definition 3 (13 Studies, 143 Patients Within 12 Months and 8 Studies, 106 Patients After 12 Months) A new HP classification system has been proposed by Med-El and Skarzynski (personal communication, 2011) Institute of Physiology and Pathology of Hearing, Warsaw, Poland, in an attempt to adopt uniformity in HP surgery. This is similar to Definition 2 in that it includes 2,000 Hz but is different in that it describes a percentage relative to the degree of preoperative lowfrequency hearing using the formula below: HP (%) = [(PTApostop Y PTApreop)/(120-PTApreop)]
100 PTA = audiogram pure-tone average of 250, 500, 1,000, 2,000 Hz Complete HP = 0%Y25% Partial HP = 25%Y60% Minimal HP = 960% Complete loss of hearing = None measurable If the information was available, the HP results were divided into those within 12 months and those after 12 months. This was with the purpose to attempt to further describe any changes in HP with time. Within 12 months, 13 of 24 studies contained results that could be interpreted according to this definition. One hundred

Data Synthesis The weighted least-squares regression method was used to determine the predictive power of each explanatory variable across all studies. All data analyses were performed with the R version 2.15.3. Only statistically significant differences are reported. Statistical significance was defined as p G 0.05.

RESULTS The results of the meta-analysis are presented in Table 2. The HP rates of individual studies are presented in Table 3 and Supplemental Digital Content 1 (http://links.lww.com/MAO/A253). In brief, pediatric populations have better HP than adults. The studies that were published more recently had worse outcomes compared with studies published longer ago. Electrode arrays that were longer did not lead to lower rates of HP. Straightelectrode arrays did not have benefit over contoured arrays. No electrode array design had an advantage. In terms of technique, cochleostomy was better than the round window approach. The posterior tympanotomy approached was better than the suprameatal approach. Using a low insertion speed of greater than 30 seconds had higher rates of HP. There was no overall benefit to using hyaluronic acid. A soft tissue seal of the cochleostomy site after electrode insertion is better than a fibrin glueYonly seal. Intraoperative steroids did not show a benefit for HP. Intraoperative transtympanic steroids given before the incision did not show any benefit. Topical steroids placed into the middle ear during surgery showed a benefit only at the 2,000-Hz frequency. Postoperative steroids showed a benefit for HP. Most of the individual variables were not correlated with each other, but some variables showed a correlation

Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HEARING PRESERVATION COCHLEAR IMPLANTATION

e259

The influence of variables of HP: Demographics

TABLE 2A.

Demographics

HP

n

Adjusted R2

Recent publication

Adults

Follow-up

Complete

329

0.81

G0.01 CCCC

0.72

Partial

329

0.4

0.91

Unsuccessful

329

0.58

0.03 CCC

Complete

173

0.84

0.92

Partial

173

0.53

0.25

Unsuccessful

173

0.67

0.16

3 (G12 months)

HP (G12)

159

0.96

G0.01 CCCC

3 (912 months)

HP (912)

96

0.99

G0.01 CCCC

G0.01 CCCC 292 vs. 37 G0.01 292 vs. 37 G0.01 CCCC 292 vs. 37 0.14 167 vs. 6 0.35 167 vs. 6 0.02 CCC 167 vs. 6 G0.01 128 vs. 31 G0.01 CCCC 69 vs. 27

Definition 1

2

G0.02 CCCC G0.02 CCCC 0.67 0.62 0.32 G0.01 CCCC 0.10

Table 2 shows the p values of the variables according to the definitions of HP. Value of p with significance G0.05 are underlined. A positive influence is bolded. A negative influence is nonbolded. A higher adjusted R2 describes how well these data are fitted. In other words, the predictive power of the variables is higher. When interpreting correlation with HP category, a higher HP category is a worse outcome. Therefore, a positive correlation with HP category indicates a worse outcome. The number of patients in each definition is presented below the p value as ‘‘n’’ versus ‘‘n.’’ The variables have been subdivided into groups (A) demographics, (B) electrode array design, (C) surgical techniques, and (D) steroid usage.The variables presented include the date of publication as a continuous variable (recent publication), adult populations (Q16 yr) compared with pediatric populations (G16 yr) (adults), and length of follow-up (follow-up).

with other variables. The correlations of the variables are presented in Table 4. The variables that had a correlation of greater than 0.5 were the use of Med-El electrodes and the length of electrode arrays (0.51), the use of topical steroids and longer study follow-up (0.58), the use of topical steroids and Med-El electrodes, the use of lubricant and the cochleostomy approach (0.64), and the use of postoperative steroids and a soft tissue cochleostomy seal (j0.54).

a lack of consistency in definition and population inclusion criteria. There is no consensus with reporting of HP results in the literature. There is controversy over the degree of deterioration of hearing loss that should be included (11) as well as the duration of preoperative highfrequency hearing loss in reporting of outcomes (12,13). It is difficult to compare studies because of varying and evolving study inclusion criteria. It must be emphasized that this meta-analysis contains studies with heterogeneity in patient inclusion criteria, definitions of hearing stability, and which pure-tone thresholds are included. It should also be recognized that a meta-analysis of cohort studies will have a publication bias. Authors are less likely to publish negative results. The patients are required to

DISCUSSION When examining the evidence of HP cochlear implantation, studies can be difficult to compare because of

TABLE 2B. The influence of variables of HP: Electrode array design Electrode array design

HP

n

Adjusted R2

Longer

Straight

Med-El vs. others

Cochlear vs. others

Complete

329

0.81

0.40

Partial

329

0.4

0.05

Unsuccessful

329

0.58

0.19

Complete

173

0.84

0.10

Partial

173

0.53

0.06

Unsuccessful

173

0.67

0.22

3 (G12 months)

HP (G12)

159

0.96

0.93

3 (912 months)

HP (912)

96

0.99

0.41

0.62 218 vs. 111 0.17 218 vs. 111 0.12 218 vs. 111 0.31 123 vs. 50 0.91 123 vs. 50 0.34 123 vs. 50 0.97 97 vs. 62 n/a

0.55 124 vs. 205 0.57 124 vs. 205 0.34 124 vs. 205 0.64 123 vs. 50 0.07 123 vs. 50 G0.01 123 vs. 50 0.04 79 vs. 80 G0.01 75 vs. 21

0.06 187 vs. 142 0.49 187 vs. 142 0.06 187 vs. 142 0.31 50 vs. 123 0.92 50 vs. 123 0.34 50 vs. 123 0.97 62 vs. 97 n/a

Definition 1

2

The variables presented include the length of the electrode array as a continuous variable (longer), straight compared with contoured electrodes (straight), Med-El arrays compared with the other companies (Med-El vs. other), and Cochlear arrays compared with the others (Cochlear vs. other). Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

e260

P. L. SANTA MARIA ET AL. TABLE 2C.

Definition

HP

1

The influence of variables of HP: Surgical techniques

Adjusted R2

n

Complete

329

0.81

Partial

329

0.4

Unsuccessful

329

0.58

Complete

173

0.84

Partial

173

0.53

Unsuccessful

173

0.67

3 (G12 months)

HP (G12)

159

0.96

3 (912 months)

HP (912)

96

0.99

2

Surgical technique Cochleostomy 0.01 CCCC 278 vs. 51 0.05 CCCC 278 vs. 51 0.83 278 vs. 51 0.45 130 vs. 43 0.22 130 vs. 43 0.31 CCCC 130 vs. 43 0.11 115 vs. 44 G0.01 85 vs. 11

Posttymp 0.24 324 vs. 5 0.14 324 vs. 5 0.22 324 vs. 5 0.05 168 vs. 5 0.21 168 vs. 5 G0.01 CCCC 168 vs. 5 G0.01 CCCC 154 vs. 5 G0.01 CCCC 91 vs. 5

Slow insertion

Lubricant

Soft tissue seal

0.07 148 vs. 174 0.13 148 vs. 174 0.85 148 vs. 174 0.75 80 vs. 86 0.30 80 vs. 86 0.27 80 vs. 86 G0.01 CCCC 34 vs. 116 0.65 60 vs. 31

G0.01 CCCC 175 vs. 154 G0.01 CCCC 175 vs. 154 G0.01 CCCC 175 vs. 154 0.60 117 vs. 56 0.10 117 vs. 56 0.08 117 vs. 56 0.02 CCCC 109 vs. 50 G0.01 CCCC 72 vs. 24

G0.01 CCCC 319 vs. 10 0.05 319 vs. 10 G0.01 CCCC 319 vs. 10 0.20 163 vs. 10 0.92 163 vs. 10 0.35 163 vs. 10 G0.01 CCCC 149 vs. 10 n/a

The variables presented include the cochleostomy approach compared with the round window approach (cochleostomy), posterior tympanotomy compared with the suprameatal approach (posttymp), slow insertion (930 s) compared with a normal insertion speed, use of lubricant compared with no lubricant use (lubricant), and a soft tissue seal compared with a fibrin glue only seal (soft tissue seal).

specifically consent to inclusion within a hearing preservation study, and there is an inability to blind the patient or observer in these studies. We recognize that, ideally, many of these factors are best examined in prospective randomized trials and call for future studies in these areas. Although the use of multiple definitions is not ideal, it allows individual readers to look at the evidence according to the definition their institution practices. When the results are not consistent across definitions, it suggests different effects of variables on different regions of the cochlea. Demographics Pediatric Populations Have Better HP Than Adults Adults are more likely to lose more decibels, have less cases of complete HP, and have more unsuccessful cases TABLE 2D. n

Adjusted R2

Complete

329

0.81

Partial

329

0.4

Unsuccessful

329

0.58

Complete

173

0.84

Partial

173

0.53

Unsuccessful

173

0.67

3 (G12 months)

HP (G12)

159

0.96

3 (912 months)

HP (912)

96

0.99

1

2

The Timing of the Studies Did Not Have a Consistent Effect on HP Outcomes Often, surgical techniques improve with time and the experience of the institution. More recent studies are likely to contain cohorts of patients implanted more recently and so the date of publication is one way to examine if the techniques of HP have improved across time. Interestingly,

The influence of variables of HP: Steroid usage

HP

Definition

of HP. This was consistent using both Definitions 1 (complete, p G 0.01; unsuccessful, p G 0.01) and 2 (unsuccessful, p = 0.04). Adults had worse results according to Definition 3 within 12 months, but after 12 months (p G 0.01), adults were more likely to have better HP than pediatric populations. The literature supports that good outcomes can be achieved in hearing preservation cochlear implantation in pediatric populations (14).

Steroids IV

Transtympanic (preincision)

Topical

Postoperative

0.82 100 vs. 229 G0.01 CCCC 100 vs. 229 G0.01 CCCC 100 vs. 229 0.02 CCCC 69 vs. 104 0.97 69 vs. 104 G0.05 CCCC 69 vs. 104 G0.01 CCCC 71 vs. 88 G0.01 CCCC 68 vs. 28

G0.01 CCCC 19 vs. 310 G0.01 CCCC 19 vs. 310 0.15 19 vs. 310 G0.01 CCCC 19 vs. 154 0.03 CCCC 19 vs. 154 0.87 19 vs. 154 G0.01 CCCC 14 vs. 145 G0.01 CCCC 19 vs. 77

0.77 106 vs. 223 0.52 106 vs. 223 0.42 106 vs. 223 G0.01 CCCC 106 vs. 67 0.04 CCCC 106 vs. 67 0.53 106 vs. 67 G0.01 CCCC 62 vs. 97 G0.01 CCCC 70 vs. 26

G0.01 CCCC 43 vs. 286 G0.01 CCCC 43 vs. 286 G0.01 CCCC 43 vs. 286 G0.01 CCCC 43 vs. 130 0.47 43 vs. 130 G0.01 CCCC 43 vs. 130 G0.01 CCCC 42 vs. 117 G0.01 CCCC 5 vs. 91

The variables presented include the use of parenteral steroids given intravenously compared with no intravenous steroids (IV) , transtympanic steroids given after induction (before incision) compared with no transtympanic steroids (transtympanic), topical steroids placed into the middle ear after mastoidectomy compared with no topical steroids (topical), and postoperative steroids compared with no postoperative steroids. Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HEARING PRESERVATION COCHLEAR IMPLANTATION TABLE 3.

e261

Summarized hearing preservations rates for studies reviewed HP results Definition 1

Primary Author Arnoldner (35) Berrettini (36) Brown (14) Bruce (37) Erixon (38) Fraysse (39) Gantz (13) Garcia-Ibanez (40) Gstoettner (41) Gstoettner (41) Gstoettner (42) Gstoettner (43) Helbig (44) James (45) James (46) Kiefer (47) Kuthubutheen (48) Punte (49) Radeloff (50) Santa Maria (10) Skarzycski (51,52) Skarzycski (53) Tamir (54) Usami (23)

Publication year

n

C (%)

2012 2008 2010 2011 2012 2006 2009 2009 2009 2009 2004 2006 2011 2005 2006 2004 2012 2010 2012 2013 2010 2007 2012 2011

5 30 31 14 20 27 68 28 7 2 21 23 18 12 10 14 5 2 2 14 120 10 19 5

0 33.3 41.9 35.7 55 3.7 47.1 25 X 0 57.1 34.8 X 0 0 42.9 0 0 0 0 X 30 X 100

Definition 3 (G12 months)

Definition 3 (912 months)

P (%)

U (%)

C (%)

Definition 2 P (%)

U (%)

HP1 (%)

HP2 (%)

HP3 (%)

HP4 (%)

HP1 (%)

HP2 (%)

HP3 (%)

HP4 (%)

0 20 0 42.9 20 44.4 25 39.3 X 0 14.3 17.4 X 16.7 0 14.3 100 100 100 21.4 X 20 X 0

100 46.7 58.1 21.4 25 51.9 27.9 35.7 X 100 28.6 47.8 X 83.3 100 42.9 0 0 0 78.6 X 50 X 0

0 X X 28.6 45 X X 35.7 X 50 61.9 39.1 X 0 10 57.1 0 50 0 0 X 30 X 100

0 X X 0 0 X X 31.1 X 0 9.5 13 X 50 10 7.1 100 50 100 35.7 X 30 X 0

100 X X 71.4 55 X X 32.1 X 50 28.6 47.8 X 50 80 35.7 0 0 0 64.3 X 40 X 0

0 X 33.3 41.4 60 X X 14.3 42.9 50 X X X 8.3 0 50 X X 0 42.9 X 60 X 100

60 X 23.8 41.4 30 X X 46.4 57.1 0 X X X 58.3 20 21.4 X X 50 50 X 10 X 0

0 X 42.9 57.1 10 X X 28.6 0 50 X X X 25 40 14.3 X X 0 7.1 X 20 X 0

40 X 0 0 0 X X 10.7 0 0 X X X 16.7 30 14.3 X X 50 0 X 10 X 0

0 X 50 X X X X X X X 52.4 43.5 X X X X 40 0 X 21.4 X X X 100

66.6 X 40 X X X X X X X 23.8 13 X X X X 20 100 X 0 X X X 0

0 X 10 X X X X X X X 9.5 8.7 X X X X 40 0 X 57.1 X X X 0

33.3 X 0 X X X X X X X 14.3 34.8 X X X X 0 0 X 7.1 X X X 0

Hearing preservation rates for the published studies referenced according to the various definitions. Supplemental Digital Content 1 (http://links.lww.com/MAO/A253) is a detailed version of Table 3 including the variables used in the analysis. C indicates complete; P, partial; U, unsuccessful; X, data not given in the individual study.

according to Definition 1, which excludes the 2,000-Hz frequency, studies published more recently had lower rates of complete HP (p G 0.01) and higher rates of unsuccessful HP (p = 0.03). The trends were the same according to Definition 2 but were not significant. Articles published more recently had better HP classifications within 12 months (p G 0.01) and also after 12 months (p G 0.01). The influence of timing was not consistent across all definitions, so we are unable to comment as to whether HP techniques have truly improved across time. Studies With Longer Follow-Up Had More Partial Hearing Preservation When patients within an individual study are followed across time, HP deteriorates at a rate worse than can be explained by the natural progression of hearing loss (10). When studies were compared with each other in our analysis, it was found that those with patient cohorts with longer follow-up have more partial HP (p G 0.01) but lower rates of complete hearing loss (p G 0.01) according to Definition 1. This could be explained by progressive deterioration of hearing, through which ‘‘complete’’ HP becomes ‘‘partial’’ HP. However, a publication bias may be present with authors less likely to present long-term follow-up of cases with unsuccessful HP. Patients being counseled for potential EAS need to be aware of the documented potential medium-term (2-yr) deterioration of their residual hearing (10).

Electrode Array Design Longer Length Electrode Arrays With Deeper Insertion Did Not Lead to Lower Rates of HP An early concept of HP surgery in cochlear implantation was that deeper insertion would lead to loss of residual hearing. Choosing the optimal electrode array was thought to be a compromise between being as short as possible to reduce damage but long enough to have adequate cochlear coverage especially if residual hearing is lost (13,15,16). Cochlear implant companies now manufacture full-length electrode arrays designed to induce minimal trauma, although it remains unclear if these are the best selection for patients with normal or aidable lowfrequency hearing. A number of studies have been recently published that reported HP with full-length array insertion (17Y21), but, on careful review of these articles, there are often dramatic drops in low-frequency hearing. In this meta-analysis, the length of the electrode array showed mixed trends depending on the definition. None of these were significant. Although the meta-analysis did not show worse outcomes with longer-length electrode arrays, the available literature still does not support the use of full insertion over partial insertion. Exactly how long an electrode array should be to give the best outcomes, in terms of hearing preservation and speech outcomes, is yet to be determined. One group suggests that the tip design is also critical when choosing an electrode array for hearing preservation (22). The use of Med-El electrode arrays was Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

e262

P. L. SANTA MARIA ET AL. TABLE 4.

Correlation of variables

Demographics

Demographics Electrode array design

Surgical technique

Steroids

Electrode array design

Recent publication

Adults

Follow-up

Longer

Straight

Med-El vs. others

Cochlear vs. others

1.00 0.01 j0.06 0.17 0.22 0.18 j0.22 j0.31 j0.35 j0.13 j0.26 0.09 j0.02 0.28 j0.08 0.06

0.01 1.00 0.01 0.11 0.27 0.20 0.07 j0.06 j0.18 0.21 j0.12 0.18 j0.37 j0.18 0.20 0.04

j0.06 0.01 1.00 j0.01 0.03 0.36 j0.36 0.20 j0.31 0.41 0.35 0.05 0.25 0.09 0.58 j0.15

0.17 0.11 j0.01 1.00 0.03 0.51 j0.49 j0.09 j0.10 0.10 0.14 0.15 0.29 j0.10 0.13 0.13

0.22 0.27 0.03 0.03 1.00 0.16 j0.10 j0.18 j0.45 j0.11 0.17 0.13 j0.39 j0.13 0.42 j0.25

0.18 0.20 0.36 0.51 0.16 1.00 j0.85 j0.29 j0.21 0.29 0.05 j0.14 0.05 0.14 0.57 0.09

j0.22 0.07 j0.36 j0.49 j0.10 j0.85 1.00 0.21 0.18 j0.21 j0.17 0.12 j0.20 j0.12 j0.49 j0.04

Recent publication Adults Follow-up Longer Straight Med-El vs. others Cochlear vs. others Cochleostomy Posttympanotomy Slow insertion Lubricant Soft tissue IV Transtympanic Topical Postoperative

Surgical technique

Steroids

Slow Cochleostomy Posttymp insertion Lubricant Demographics

Recent publication Adults Follow-up Electrode array Longer design Straight Med-El vs. others Cochlear vs. others Surgical Cochleostomy technique Posttympanotomy Slow insertion Lubricant Soft tissue Steroids IV Transtympanic Topical Postoperative

j0.31 j0.06 0.20 j0.09 j0.18 j0.29 0.21 1.00 j0.07 0.27 0.64 0.34 0.22 j0.08 0.10 j0.47

j0.35 j0.18 j0.31 j0.10 j0.45 j0.21 0.18 j0.07 1.00 0.26 j0.29 j0.09 0.35 0.09 j0.37 0.16

j0.13 0.21 0.41 0.10 j0.11 0.29 j0.21 0.27 0.26 1.00 0.10 0.18 0.26 0.08 0.38 j0.33

j0.26 j0.12 0.35 0.14 0.17 0.05 j0.17 0.64 j0.29 0.10 1.00 0.30 0.21 j0.30 0.33 j0.40

Soft tissue

IV

0.09 0.18 0.05 0.15 0.13 j0.14 0.12 0.34 j0.09 0.18 0.30 1.00 0.24 0.06 0.24 j0.54

j0.02 j0.37 0.25 0.29 j0.39 0.05 j0.20 0.22 0.35 0.26 0.21 0.24 1.00 0.25 j0.14 0.01

Transtympanic Topical Postoperative 0.28 j0.18 0.09 j0.10 j0.13 0.14 j0.12 j0.08 0.09 0.08 j0.30 0.06 0.25 1.00 0.25 j0.11

j0.08 0.20 0.58 0.13 0.42 0.57 j0.49 0.10 j0.37 0.38 0.33 0.24 j0.14 0.25 1.00 j0.44

0.06 0.04 j0.15 0.13 j0.25 0.09 j0.04 j0.47 0.16 j0.33 j0.40 j0.54 0.01 j0.11 j0.44 1.00

Correlation of variables examined. Values closer to 1 indicate a stronger correlation (or j1 in the case of negative correlation). Correlations greater than 0.5, or less than j0.5, have been highlighted in bold.

correlated with the use of longer electrode arrays (correlation coefficient of 0.51) in this meta-analysis. This is likely caused by Med-El more recently releasing a longer ‘‘hearing preservation’’ electrode array than Cochlear that now has a variety of lengths available with design features for hearing preservation. Straight-Electrode Array Designs Did Not Show Benefit Over Contoured Electrode Arrays Electrode array designs for HP have favored straightelectrode arrays so that run on the outer wall of the cochlea rather than against the modiolus (15). In this metaanalysis, there was no statistically significant benefit of straight-electrode arrays compared with contoured electrode arrays. There are a number of studies reporting hearing preservation using contoured electrode arrays (19,20), and there was no difference found in this meta-analysis between straight and contoured electrode arrays to preserve hearing.

No Electrode Array Design Showed an Advantage Over Another The electrode array designs used by the studies included in this meta-analysis included Cochlear’s (Melbourne, Victoria, Australia) Nucleus 24-K, 24-Contour, Contour Advance, and Iowa Nucleus; Med-El’s (Med-El, Innsbruck, Austria) FlexEAS, FlexSoft, Combi 40+, Standard, and Custom; and also Advanced Bionics (Valencia, CA, USA) HiFocus Helix and Hifocus 1j. No particular electrode array showed a significant advantage over another. When grouped according to company, no one company’s electrode arrays had a significant advantage over the others. The analysis was also performed by grouping electrode array designs according to groups that are marketed as HP electrode arrays against those which are not in cluding Med-El FlexEAS and Med-El FlexSoft versus Cochlear 24-Contour and Cochlear Contour Advance versus MedEl Combi40+ and Med-El Standard. There were no significant advantages for any group of electrode arrays. The

Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HEARING PRESERVATION COCHLEAR IMPLANTATION

FIG. 1.

e263

Methodology according to PRISMA (9).

lack of difference found between electrode array types should be interpreted with caution. The individual numbers of separate electrode array types used in the meta-analysis is small and, therefore, only likely to detect a very large difference between types. Surgical Technique Cochleostomy Is Better Than Round Window Insertion There has been an ongoing debate between surgeons as to whether the cochleostomy or the round window

approach leads to better HP. Advocates for the round window approach argue that this approach minimizes drilling time with less noise exposure to the cochlea and the potential for reduced damage to intracochlear structures (17,22,23). According to Definition 1, the cochleostomy approach is more likely to give higher rates of complete HP (p = 0.01) and a trend to less rates of partial HP (p = 0.05). If the 2,000-Hz frequency is taken into account, as in Definition 2, the cochleostomy approach has a trend toward more rates of complete and partial HP and a trend away from unsuccessful HP. There Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

e264

P. L. SANTA MARIA ET AL.

was also a significant difference between techniques according to HP classification, with cochleostomy being the favored technique after 12 months (p G 0.01). There is also a trend within 12 months. The round window approach did not lead to better results according to any definition. The use of lubricant was correlated with the cochleostomy approach (correlation coefficient, 0.64); however, the cochleostomy approach itself was a factor leading to higher rates of HP. As defined in the methods, we were unable to distinguish between true cochleostomy and extended round window approaches in most articles, and these were combined together for analysis. By combining these two techniques, we are unable to comment on whether a cochleostomy or an extended round window approach provides better outcomes than the other. The benefit from the cochleostomy approach may be because it gives the most direct line for electrode array insertion into the cochlea. Navigating the hook region via the round window approach may also cause more trauma to the basilar membrane (18,21). The Posterior Tympanotomy Approach Is Better Than the Suprameatal Approach A mastoidectomy with a posterior tympanotomy approach trended toward higher rates of complete HP and statistically significant lower rates of unsuccessful HP according to two (complete, p = 0.05; unsuccessful, p G 0.01). The results are mixed when using Definition 3 as the posterior tympanotomy approach is favored within 12 months but less favored after 12 months. The different approaches give a different first point of contact during electrode array insertion. The angle of the suprameatal approach to the cochlear may also lead to a slightly different angle to create a cochleostomy. The metaanalysis suggests that the suprameatal approach is the inferior approach for hearing preservation. Slow Insertion Speed Is Better Than an Insertion Speed of Less Than 30 Seconds Using a slow and steady insertion speed for electrode array insertion reduces the fluid forces within the cochlear compared with faster insertion speeds (24). In this metaanalysis, studies using a slow insertion speed showed a trend toward higher rates of complete HP according to Definition 1 (p = 0.07) and significantly better rates in HP classification within 12 months (p G 0.01). Most studies reported a slow insertion speed without giving a time for insertion. Other studies reported insertion speeds of 30 to 180 seconds for the electrode array. Those studies that did not comment on insertion speed were considered as ‘‘normal’’ insertion speed and for the purpose of this analysis were assumed to be less than 30 seconds. There is the possibility that the authors who did not comment may have used a slow insertion and it is unlikely that they were necessarily fast or careless. Regardless, if aiming to preserve hearing up to 1,000 Hz, those studies reporting slow insertion speed had more hearing preservation. How slow insertion speed should be is not clear. There is some evidence stating that, the slower the insertion speed, the better (25).

Using Hyaluronic Acid as a Lubricant for Insertion Did Not Show an Overall Benefit Studies using hyaluronic acid based lubricants had lower rates of complete HP (p G 0.01) and higher rates of unsuccessful HP (p G 0.01) according to Definition 1. If the 2,000-Hz frequency is included, using Definition 2, using hyaluronic acid has a trend toward higher rates of unsuccessful HP (p = 0.08). Using the HP classification, lubricant favors poorer hearing classification within 12 months (p G 0.01) but leads to higher HP after 12 months (p G 0.01). The concept of injury after implantation is complex and still not fully understood. Certainly, at the time of implantation, there is the potential for direct trauma, but after implantation during healing, there is the potential for further injury, which is yet to be defined. We do know that residual hearing can deteriorate faster than that can be explained otherwise after cochlear implantation HP surgery (10). The idea of using a lubricant is to reduce friction trauma during electrode array insertion and potentially reduce the amount of blood and bone dust that enters the inner ear, but potentially, there is a component in the lubricant that leads to greater injury, or the viscosity of the lubricant alters the fluid dynamics during insertion potentially causing more trauma. Lubricant users were also more likely to use the cochleostomy approach (correlation coefficient of 0.64). A Soft Tissue Seal for the Cochleostomy Is Better Than a Fibrin GlueYOnly Seal Authors generally use either a soft tissue seal such as muscle or fascia to seal the cochleostomy after implantation or fibrin glue. Those studies using fibrin glue had less complete HP (p G 0.01) and higher rates of unsuccessful HP (p G 0.01) according to Definition 1 and within 12 months according to Definition 3. There was no difference between techniques using Definition 2. It is unknown why those sealed with fibrin glue performed worse. A seal with fibrin glue may allow for greater perilymph leak or may induce more inflammation within the cochlea. There is no research examining the possible effects of fibrin glue on the cochlea. Steroids Intraoperative Parenteral Steroids Did Not Show a Benefit Steroids are commonly used in the hearing preservation literature. There have been a number of animal studies supporting the use of steroids for hearing preservation in cochlear implantation (26,27) as well as work toward a steroid-eluting electrode array (28). Studies reporting the use of intraoperative intravenous steroids were compared with studies where no intraoperative intravenous steroids were mentioned. It is recognized that intravenous steroids are commonly given by the anesthesiologist during surgery and sometimes without the knowledge of the surgeon. It is difficult therefore to make a conclusion on this variable based on varied results on HP and the likelihood that a number of patients in the

Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HEARING PRESERVATION COCHLEAR IMPLANTATION noYintraoperative intravenous steroids actually received steroids. Studies reporting use of intraoperative intravenous steroids showed more hearing loss (p = 0.03) according to Definition 1 but more complete HP (p G 0.01) and less rates of unsuccessful HP (p = 0.02) according to Definition 2. Intraoperative intravenous steroids showed worse HP classification both within 12 months (p G 0.01) and after 12 months (p G 0.01). Intraoperative Preincision Transtympanic Steroids Did Not Show a Benefit Some authors advocate injecting transtympanic steroids before or shortly after induction of anesthesia before making an incision over the mastoid. The aim of this is to give more time (the time it takes to perform a mastoidectomy) for the steroids to diffuse through the round window and other routes. The meta-analysis reveals that this practice leads to less complete HP (Definition 1, p G 0.01; Definition 2, p G 0.01) but higher rates (Definition 1, p G 0.01; Definition 2, p G 0.01) of partial HP (between 10 and 20 dB change from preoperative PTA to postoperative PTA). The mechanism of action of this method of steroids is most likely to be the same as the intraoperative topical steroids with the longer time for effect till electrode array insertion. Intraoperative Topical Steroids Showed a Benefit for Preservation of 2,000 Hz The practice of using topical steroids onto the surgical field and onto the cochleostomy or round window immediately before electrode array insertion does not have any effect on HP according to Definition 1. Including the 2,000-Hz frequency in Definition 2 and in the HP classification within 12 months reveals that topical steroids have higher rates of HP (p G 0.01 and p G 0.01). There was no difference of effect on HP classification after 12 months. Intraoperative topical steroid administration was not shown to have any harm in this metaanalysis. However, its lack of effect on frequencies 250 to 1,000 Hz suggests that the ability of the steroids to reach the apical region of the cochlear may be limited. This is reflected in animal studies that suggest that the parenteral route is the best for covering the apical region and the round and oval windows being best for the basal region (29). The lack of consistency in dosing and application time is likely to produce inconsistent results. The topical steroid most commonly used was triamcinolone 40 mg/mL; however, methylprednisolone up to 125 mg/mL was also used. According to animal studies, the time for effect of topical steroids can be reduced by increasing the dose (30). If committing to the use of topical steroid therapy, it would make sense to commit to the highest available dose to achieve the greatest effect and minimize the application time. The use of topical steroids correlated with the use of Med-El electrode arrays (correlation coefficient of 0.57), indicating that surgeons using this device are more likely to give topical steroids in hearing preservation surgery. This is not a confounding factor in this

e265

meta-analysis because the analysis used accounts for the correlation between variables. Postoperative Oral Steroids Showed Benefit Over No Postoperative Steroids At the time of electrode array insertion, injury, cell injury, and inflammation occur and the effects are likely to last longer than the period topical steroids act on the inner ear. Postoperative steroids potentially provide a longer-acting method of reducing cell injury and inflammation after insertion. Giving postoperative steroids orally leads to more complete HP and less unsuccessful HP using Definitions 1 (complete, p G 0.01; unsuccessful, p G 0.01) and 2 (complete, G0.01; unsuccessful, p G 0.01). Using the HP classification, studies using postoperative steroids have a worse outcome within 12 months (p G 0.01) with better outcomes after 12 months. The numbers of studies and patients able to be included within Definitions 1 and 2 are much larger than those that can be included for the HP classification, and the outcome of the variable is judged on the results with the greater statistical power. The most common protocol used in the studies was milligrams per kilogram of prednisone (up to 60 mg) for 4 weeks. There Is a Need for Standardized Reporting for Cochlear Implantation Intended to Preserve Acoustic Hearing There is a need for a global standard of reporting acoustic hearing changes after cochlear implantation intended to preserve acoustic hearing. Our review of this topic has shown wide variability in how these outcomes are reported and differences in the favorability of outcomes depending on which scheme is used. It is most important to determine whether hearing preservation surgery results in better patient outcomes not just pure-tone thresholds but also speech discrimination, particularly in noise, as well as music recognition and appreciation and quality of life. It would also be useful to determine if outcomes were improvedVwhether this was from the combined electroacoustic stimulation or the electrical only stimulation. We previously reported in a small series that there was no significant difference in speech outcomes and quality of life between those who had hearing preservation and those who did not, with patients receiving significant benefit from electrical stimulation only (10). Unfortunately, the majority of studies do not report these outcomes, and our analysis is therefore unable to comment on these more important outcomes. Based on our analysis of the current literature, we call for efforts to reach a global consensus on how this should be done in the future, and also we put forth additional recommendations to be considered when creating these standards. In considering this topic, one must keep in mind that there are two related, but distinctly different, types of outcomes to consider. The first has to do with outcomes of combined bimodal electric and acoustic cochlear stimulation that focus on comparisons between bimodal stimulation and other rehabilitative options such as conventional hearing aids or standard cochlear implantation. These outcomes use functional audiometric testing Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

e266

P. L. SANTA MARIA ET AL. TABLE 5.

Outcomes of variables in cochlear implantation surgery aiming for preserving low-frequency hearing

Electrode array design Surgical technique

Steroids

Conclusion

HP outcome

Longer electrode array length Straight vs. contoured electrode array Electrode array type Cochleostomy vs. round window Posterior tympanotomy vs. suprameatal approach Slow insertion speed (Q30 s) Lubricant use Soft tissue seal vs. fibrin glue seal of cochleostomy Intraoperative IV Intraoperative transtympanic Intraoperative topical Postoperative oral

No disadvantage No difference No difference Benefit Benefit Benefit No advantage Benefit No advantage No advantage Benefit at 2,000 Hz Benefit

Summary of outcomes of variables in cochlear implantation surgery aiming to preserve low-frequency hearing. The hearing preservation (HP) outcome is bolded.

such as hearing in background noise, pitch perception, and music appreciation. However, important as these may be, our intent, however, is to provide recommendations only for reporting on the relatively straightforward topic of hearing threshold changes after cochlear implantation intended to preserve acoustic hearing, which may be a component of a bimodal strategy or perhaps just an indicator of surgical trauma. The first thing to consider is that a classification system for HP should include thresholds at frequencies commonly measured by the audiologist and should reflect the differentiation within the literature between low-frequency hearing (pure-tone thresholds up through 1,000 Hz) and middle-frequency hearing (pure-tone thresholds from 2,000 through 3,000 Hz), thereby allowing for a calculation of preservation within each of these zones independently. The definition of low-frequency hearing up to 1,000 Hz is the most common definition used in the cochlear implantation hearing preservation literature, used in 79% of studies in our meta-analysis. For most patients, the primary consideration will involve preservation of low-frequency hearing because usable residual middle-frequency hearing is less common among these patients and because most cochlear implant electrode arrays account for middle-frequency

TABLE 6.

hearing electrically (unless the surgeon attempts to map the cochlea preoperatively and choose a custom insertion depth accordingly). Inclusion of the threshold at 2,000 Hz in the calculation alongside low frequencies, as demonstrated in our meta-analysis, can skew the results. If middlefrequency preservation at 2,000 Hz is desired, it not only should be classified separately but also should account for 3,000 Hz when possible. The importance of 3,000 Hz in functional hearing outcomes has been highlighted in prior standardized reporting guidelines such as those set forth by the American Academy of OtolaryngologyYHead and Neck Surgery in reporting surgical outcomes (31). These guidelines provide a foundation for reporting standards but are not intended to cover low-frequency hearing preservation in cochlear implantation. A standardized reporting system will allow variables, interventions, and techniques to be compared across institutions to observe the best outcomes in hearing preservation. In the future, high-frequency HP may also be desired, and this modification takes into account possible future needs. The second item to consider is that not only must hearing preservation guidelines address pure-tone threshold averages but also there should be some attempt to account for whether an aidable status has been

Proposed standards for reporting hearing preservation surgery in cochlear implantation Low

Included frequencies (Hz) HP (%)

Minimum requirements

250, 500, 1,000

Middle

2,000, 3,000

High

4,000, 6,000, 8,000

Complete/near complete 0Y20, and PTA G90 dB Partial 20Y50, and PTA G90 dB Nonaidable but measurable 50Y99, or 990 dB No measurable hearing None measurable Report inclusion criteria including pure tone, speech scores, and contralateral ear thresholds. Patients should not be excluded based on outcomes (e.g., if residual hearing was lost) Report raw audiograms if n e 20 Report speech outcomes both in quiet and in noise

Proposed standards for hearing preservation reporting. Hearing Preservation (%) = [(PTApostop Y PTApreop)/(120-PTApreop)]
100. Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HEARING PRESERVATION COCHLEAR IMPLANTATION preserved. Although there is some ambiguity as to what rightly constitutes nonaidable hearing in terms of audiometric testing benchmarks, reasonable and conservative cutoffs do exist. For example, there seems to be little doubt that preserved pure-tone thresholds at or above the 90 dB HL mark (cutoff for profound hearing loss and functional deafness) are highly unlikely to be useful from a conventional amplification standpoint and therefore should not be considered within the realm of preserved hearing. In patients with low- and middle-frequency puretone thresholds within the moderately severe and severe ranges (56Y89 dB HL), a determination of aidability will additionally rely on speech audiometry. In English, this is typically portrayed by aided open set speech testing of monosyllabic words in quiet or other similar basic standardized means in other languages. Scores below 40% would seem to indicate absence of aidable hearing because this has been used as a traditional conservative cutoff for standard cochlear implant candidacy (32). Ideally, this classification would take into account word recognition scores; however, a lack of consistency in testing protocols among institutions and among languages renders this difficult. Nonetheless, researchers should be encouraged to report preoperative and postoperative word recognition testing in the context of aidability as a separate outcome accounting in future reports. Residual acoustic hearing is also only a part of the outcome measurement of EAS procedures. How patients perform in their best aided electroacoustic setting is ultimately the measure of success when considering HP procedures. Finally, it is necessary to account for the maximum limits of an audiometer typically around 120 dB. We realize that there is some minor variability in this respect depending on hardware and other particulars; however, unless some benchmark in testing is set, a statistical method for standardization cannot be attained. In addition, it must be noted that lower-frequency measures may reflect vibrotactile perception, which is difficult to discriminate from low-frequency auditory perception. The lower the frequency, the lower the threshold at which vibrotactile perception occurs. There is variation among individuals and transducers, but at 125 Hz, vibrotactile perception occurs at approximately 30 dB (33,34). Thus, including thresholds at 125 Hz in reporting HP will dramatically and artificially elevate results. The value 250 Hz has a vibrotactile threshold at approximately 30 dB if testing bone conduction at the mastoid; however, the threshold is shifted to approximately 95 dB (but may be as low as 80 dB) if earphones are used (33). As such, it is more reasonable to use 250 Hz as the lower limit of testing low-frequency hearing in this setting, although claims of preserving hearing sensitivity at this frequency beyond 80 dB must be interpreted with caution and institutions must be careful in the method of obtaining thresholds at 250 Hz. Given these considerations, we propose the following guidelines based on a modification of what has been previously proposed by Skarzynski, which also takes into account thresholds at frequencies commonly measured

e267

and recommended by the American Speech Language Association (34) (Table 6). Typically, the ultimate goal of hearing preservation cochlear implant surgery is to allow postoperative bimodal stimulation of the cochlea, and the modifications depicted here keep this fact in mind. The percentage change allowed in complete preservation should fall within the accepted day-to-day variation of the audiogram. Also, it is recommended that future outcomes be presented in a clear table format that allows full portrayal of preoperative and postoperative auditory thresholds among the cohort. With standardization of reporting, it will be useful in the future to study whether patients with differing degrees of preoperative residual hearing lead to worse HP outcomes. The above arguments form the basis of the proposed HP classification: Hearing Preservation (%) = [(PTApostop Y PTApreop)/ (120-PTApreop)]
100 PTA = audiogram pure-tone average Low-frequency PTA = thresholds at 250, 500, 1,000 Hz Middle-frequency PTA = thresholds at 2,000, 3,000 Hz High frequency PTA = thresholds at 4,000, 6,000, 8,000 Hz With this classification, the categories of low-, middle-, and high-frequency hearing preservation would be reported separately. The PTA used in the calculation would reflect whether it is low, middle, or high HP. Category HP1 (Complete/Near-Complete Preservation) HP = 0%Y20% of preoperative hearing preserved, and PTA G90 dB Category HP2 (Partial Preservation) HP = 20%Y50% of preoperative hearing, and PTA G90 dB Category HP3 (Nonaidable but Measureable Hearing Preservation) HP = 950%, or PTA 990 dB Category HP4 (No Measureable Hearing Preserved)

CONCLUSION The factors giving benefit for hearing preservation in cochlear implantation are presented in Table 5, and the proposed standards for reporting HP outcomes are presented in Table 6. In summary, according to this metaanalysis, the following factors are associated with better HP: Cochleostomy approach over the round window approach, posterior tympanotomy over the suprameatal approach, a slow insertion technique over insertion of less than 30 seconds, a soft tissue seal over a fibrin glueYonly seal, the use of postoperative steroids over no postoperative steroids. Longer electrode arrays were not associated with less low-frequency HP. Topical steroid use and the use of lubricant for electrode array insertion did not give an advantage in rates of low-frequency HP.

REFERENCES 1. Hodges AV, Schloffman J, Balkany T. Conservation of residual hearing with cochlear implantation. Am J Otol 1997;18:179Y83. Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

e268

P. L. SANTA MARIA ET AL.

2. von Ilberg C, Kiefer J, Tillein J, et al. Electric-acoustic stimulation of the auditory system. New technology for severe hearing loss. ORL J Otorhinolaryngol Relat Spec 1999;61:334Y40. 3. Brockmeier SJ, Peterreins M, Lorens A, et al. Music perception in electric acoustic stimulation users as assessed by the Mu.S.I.C. test. Adv Otorhinolaryngol 2010;67:70Y80. 4. Gfeller K, Turner C, Oleson J, et al. Accuracy of cochlear implant recipients on pitch perception, melody recognition, and speech reception in noise. Ear Hear 2007;28:412Y23. 5. Gfeller KE, Olszewski C, Turner C, et al. Music perception with cochlear implants and residual hearing. Audiol Neurootol 2006; 11:12Y5. 6. Gstoettner WK, van de Heyning P, O’Connor AF, et al. Electric acoustic stimulation of the auditory system: results of a multi-centre investigation. Acta Otolaryngol 2008;128:968Y75. 7. Gantz BJ, Turner CW. Combining acoustic and electrical hearing. Laryngoscope 2003;113:1726Y30. 8. Skarzynski H, Lorens A, D’Haese P, et al. Preservation of residual hearing in children and post-lingually deafened adults after cochlear implantation: an initial study. ORL J Otorhinolaryngol Relat Spec 2002;64:247Y53. 9. Moher D, Liberati A, Tetzlaff J, et al. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. J Clin Epidemiol 2009;62:1006Y12. 10. Santa Maria PL, Domville-Lewis C, Sucher CM, Chester-Browne R, Atlas MD. Hearing preservation surgery for cochlear implantationV hearing and quality of life after two years. Otol Neurotol 2013;34: 526Y31. 11. Yao WN, Turner CW, Gantz BJ. Stability of low-frequency residual hearing in patients who are candidates for combined acoustic plus electric hearing. J Speech Lang Hear Res 2006;49:1085Y90. 12. Lenarz T, Stover T, Buechner A, et al. Hearing conservation surgery using the Hybrid-L electrode. Results from the first clinical trial at the Medical University of Hannover. Audiol Neurootol 2009; 14:22Y31. 13. Gantz BJ, Hansen MR, Turner CW, et al. Hybrid 10 clinical trial: preliminary results. Audiol Neurootol 2009;14:32Y8. 14. Brown RF, Hullar TE, Cadieux JH, et al. Residual hearing preservation after pediatric cochlear implantation. Otol Neurotol 2010;31:1221Y6. 15. Soda-Merhy A, Gonzalez-Valenzuela L, Tirado-Gutierrez C. Residual hearing preservation after cochlear implantation: comparison between straight and perimodiolar implants. Otolaryngol Head Neck Surg 2008;139:399Y404. 16. Skarzynski H, Lorens A, Matusiak M, et al. Partial deafness treatment with the nucleus straight research array cochlear implant. Audiol Neurootol 2012;17:82Y91. 17. Roland PS, Wright CG, Isaacson B. Cochlear implant electrode insertion: the round window revisited. Laryngoscope 2007;117: 1397Y402. 18. Li PM, Wang H, Northrop C, et al. Anatomy of the round window and hook region of the cochlea with implications for cochlear implantation and other endocochlear surgical procedures. Otol Neurotol 2007;28:641Y8. 19. Cosetti MK, Friedmann DR, Zhu BZ, et al. The effects of residual hearing in traditional cochlear implant candidates after implantation with a conventional electrode. Otol Neurotol 2013;34:516Y21. 20. Carlson ML, Driscoll CL, Gifford RH, et al. Implications of minimizing trauma during conventional cochlear implantation. Otol Neurotol 2011;32:962Y8. 21. Gibson D, Gluth MB, Whyte A, et al. Rotation of the osseous spiral lamina from the hook region along the basal turn of the cochlea: results of a magnetic resonance image anatomical study using highresolution DRIVE sequences. Surg Radiol Anat 2012;34:781Y5. 22. Briggs RJ, Tykocinski M, Xu J, et al. Comparison of round window and cochleostomy approaches with a prototype hearing preservation electrode. Audiol Neurootol 2006;11(Suppl 1):42Y8. 23. Usami S, Moteki H, Suzuki N, et al. Achievement of hearing preservation in the presence of an electrode covering the residual hearing region. Acta Otolaryngol 2011;131:405Y12. 24. Kontorinis G, Lenarz T, Stover T, et al. Impact of the insertion speed of cochlear implant electrodes on the insertion forces. Otol Neurotol 2011;32:565Y70.

25. Rajan GP, Kontorinis G, Kuthubutheen J. The effects of insertion speed on inner ear function during cochlear implantation: a comparison study. Audiol Neurootol 2013;18:17Y22. 26. Eastwood H, Chang A, Kel G, et al. Round window delivery of dexamethasone ameliorates local and remote hearing loss produced by cochlear implantation into the second turn of the guinea pig cochlea. Hear Res 2010;265:25Y9. 27. Connolly TM, Eastwood H, Kel G, et al. Pre-operative intravenous dexamethasone prevents auditory threshold shift in a guinea pig model of cochlear implantation. Audiol Neurootol 2011;16: 137Y44. 28. Niedermeier K, Braun S, Fauser C, et al. A safety evaluation of dexamethasone-releasing cochlear implants: comparative study on the risk of otogenic meningitis after implantation. Acta Otolaryngol 2012;132:1252Y60. 29. Maini S, Lisnichuk H, Eastwood H, et al. Targeted therapy of the inner ear. Audiol Neurootol 2009;14:402Y10. 30. Chang A, Eastwood H, Sly D, et al. Factors influencing the efficacy of round window dexamethasone protection of residual hearing post-cochlear implant surgery. Hear Res 2009;255:67Y72. 31. Gurgel RK, Jackler RK, Dobie RA, et al. A new standardized format for reporting hearing outcome in clinical trials. Otolaryngol Head Neck Surg 2012;147:803Y7. 32. Mowry SE, Woodson E, Gantz BJ. New frontiers in cochlear implantation: acoustic plus electric hearing, hearing preservation, and more. Otolaryngol Clin North Am 2012;45:187Y203. 33. Boothroyd A, Cawkwell S. Vibrotactile thresholds in pure tone audiometry. Acta Otolaryngol 1970;69:381Y7. 34. Working Group on Manual Pure-Tone Threshold Audiometry. Guidelines for manual pure-tone threshold audiometry. ASHA 1978; 20:297Y301. 35. Arnoldner C, Gstoettner W, Riss D, et al. Residual hearing preservation using the suprameatal approach for cochlear implantation. Wien Klin Wochenschr 2011;123:599Y602. 36. Berrettini S, Forli F, Passetti S. Preservation of residual hearing following cochlear implantation: comparison between three surgical techniques. J Laryngol Otol 2008;122:246Y52. 37. Bruce IA, Bates JE, Melling C, et al. Hearing preservation via a cochleostomy approach and deep insertion of a standard length cochlear implant electrode. Otol Neurotol 2011;32:1444Y7. 38. Erixon E, Kobler S, Rask-Andersen H. Cochlear implantation and hearing preservation: results in 21 consecutively operated patients using the round window approach. Acta Otolaryngol 2012;132: 923Y31. 39. Fraysse B, Macias AR, Sterkers O, et al. Residual hearing conservation and electroacoustic stimulation with the nucleus 24 contour advance cochlear implant. Otol Neurotol 2006;27:624Y33. 40. Garcia-Ibanez L, Macias AR, Morera C, et al. An evaluation of the preservation of residual hearing with the Nucleus Contour Advance electrode. Acta Otolaryngol 2009;129:651Y64. 41. Gstoettner W, Helbig S, Settevendemie C, et al. A new electrode for residual hearing preservation in cochlear implantation: first clinical results. Acta Otolaryngol 2009;129:372Y9. 42. Gstoettner W, Kiefer J, Baumgartner WD, et al. Hearing preservation in cochlear implantation for electric acoustic stimulation. Acta Otolaryngol 2004;124:348Y52. 43. Gstoettner WK, Helbig S, Maier N, et al. Ipsilateral electric acoustic stimulation of the auditory system: results of long-term hearing preservation. Audiol Neurootol 2006;11:49Y56. 44. Helbig S, Van de Heyning P, Kiefer J, et al. Combined electric acoustic stimulation with the PULSARCI(100) implant system using the FLEX(EAS) electrode array. Acta Otolaryngol 2011;131: 585Y95. 45. James C, Albegger K, Battmer R, et al. Preservation of residual hearing with cochlear implantation: how and why. Acta Otolaryngol 2005;125:481Y91. 46. James CJ, Fraysse B, Deguine O, et al. Combined electroacoustic stimulation in conventional candidates for cochlear implantation. Audiol Neurootol 2006;11(Suppl 1):57Y62. 47. Kiefer J, Gstoettner W, Baumgartner W, et al. Conservation of lowfrequency hearing in cochlear implantation. Acta Otolaryngol 2004; 124:272Y80.

Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.

HEARING PRESERVATION COCHLEAR IMPLANTATION 48. Kuthubutheen J, Hedne CN, Krishnaswamy J, et al. A case series of paediatric hearing preservation cochlear implantation: a new treatment modality for children with drug-induced or congenital partial deafness. Audiol Neurootol 2012;17:321Y30. 49. Punte AK, Vermeire K, Van de Heyning P. Bilateral electric acoustic stimulation: a comparison of partial and deep cochlear electrode insertion. A longitudinal case study. Adv Otorhinolaryngol 2010;67: 144Y52. 50. Radeloff A, Shehata-Dieler W, Scherzed A, et al. Intraoperative monitoring using cochlear microphonics in cochlear implant patients with residual hearing. Otol Neurotol 2012;33:348Y54.

e269

51. Skarzynski H, Lorens A, Piotrowska A, et al. Hearing preservation in partial deafness treatment. Med Sci Monit 2010;16:CR555Y62. 52. Skarzynski H, Lorens A. Electric acoustic stimulation in children. Adv Otorhinolaryngol 2010;67:135Y43. 53. Skarzynski H, Lorens A, Piotrowska A, et al. Preservation of low frequency hearing in partial deafness cochlear implantation (PDCI) using the round window surgical approach. Acta Otolaryngol 2007; 127:41Y8. 54. Tamir S, Ferrary E, Borel S, et al. Hearing preservation after cochlear implantation using deeply inserted flex atraumatic electrode arrays. Audiol Neurootol 2012;17:331Y7.

Otology & Neurotology, Vol. 35, No. 10, 2014

Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.