- Email: [email protected]
Nucleus Freedom North American clinical trial
Otolaryngology–Head and Neck Surgery (2007) 136, 757-762
ORIGINAL RESEARCH
Nucleus Freedom North American clinical trial Thomas Balkany, MD, Annelle Hodges, PhD, Christine Menapace, MA, Linda Hazard, MS, Colin Driscoll, MD, Bruce Gantz, MD, David Kelsall, MD, William Luxford, MD, Sean McMenomy, MD, J. Gail Neely, MD, Brian Peters, MD, Harold Pillsbury, MD, Joseph Roberson, MD, David Schramm, MD, Steven Telian, MD, Susan Waltzman, PhD, Brian Westerberg, MD, and Stacy Payne, MS, Rochester, and New York, NY; Jacksonville and Miami, FL OBJECTIVE: To evaluate hearing outcomes and effects of stimulation rate on performance with the Nucleus Freedom cochlear implant (Cochlear Americas, Denver, CO). STUDY DESIGN AND SETTING: Randomized, controlled, prospective, single-blind clinical study using single-subject repeated measures (A-B-A-B) design at 14 academic centers in the United States and Canada and comparison with outcomes of a prior device by the same manufacturer. PATIENTS: Seventy-one severely/profoundly hearing impaired adults. RESULTS: Seventy-one adult recipients were randomly programmed in two different sets of rate: ACE or higher rate ACE RE. Mean scores for Consonant Nucleus Consonant words is 57%, Hearing in Noise Test (HINT) sentences in quiet 78%, and HINT sentences in noise 64%. Sixty-seven percent of subjects preferred slower rates of stimulation, and performance did not improve with higher rates of stimulation using this device. CONCLUSIONS: Subjects performed well, and there was no advantage to higher stimulation rates with this device. From the University of Miami Ear Institute, Miami, FL (Drs Balkany and Hodges); Cochlear Americas, Denver, CO (Drs Menapace and Hazard); Mayo Clinic Rochester, Rochester, MN (Dr Driscoll); University of Iowa, Iowa City, IA (Dr Gantz); Rocky Mountain Ear Center, Denver, CO (Dr Kelsall); House Ear Clinic, Los Angeles, CA (Dr Luxford); Oregon Health Science Center, Portland, OR (Dr McMenomy); Washington University, St. Louis, MO (Dr Neely); Dallas Otolaryngology Association, Dallas, TX (Dr Peters); University of North Carolina, Chapel Hill, NC (Dr Pillsbury); California Ear Institute, Palo Alto, CA (Dr Roberson); Ottawa Hospital, Civic Campus, Ottawa, Ontario (Dr Schramm); University of Michigan, Ann Arbor, MI (Dr Telian); New York University, New York, NY (Dr Waltzman); St. Paul’s Hospital, Vancouver, BC (Dr Westerberg); and Nemours Clinic Jacksonville (Dr Payne). Disclosures: Thomas Balkany: consultant: Cochlear Americas, Advanced Bionics, Med EL Corporation; Christine Menapace: employee: Cochlear Ameri-
SIGNIFICANCE: Higher stimulation rates do not necessarily result in improved performance. © 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved.
C
ochlear implant (CI) outcomes have improved over the past 10 years,1 and much of this progress may be attributable to the development of more sophisticated CI technology. The 6-month data reported here are from a multicenter, prospective, randomized clinical trial designed to evaluate performance aspects of the Nucleus Freedom CI and include effects of stimulation rate on speech recognition. This device was introduced into clinical trials in North America in June of 2004 and incorporated a number of putative technological improvements to its predecessor, the Nucleus 24 Contour. Among these changes, the newer receiver stimulator is capable of faster rate speech-processing strategies. This study was performed at 14 experienced centers in
cas; Linda Hazard: employee: Cochlear Americas, Principal Clinical Studies Specialist; Colin Driscoll: consultant: Cochlear Americas; Bruce Gantz: consultant: Medtronics, Ansbach; David Kelsall: consultant/Speaker’s Bureau: Cochlear Americas, William Luxford: consultant/Speakers Bureau: Cochlear Americas, M. Cochlear Corp and Advanced Bionics, Medical Advisory Board; Sean McMenomy: Medical Advisory Board: Cochlear Americas; Joseph Roberson: consultant/Medical Advisory Board: Cochlear Americas, consultant: Acclarent/ Medtronic, NeuroPace; Steven Telian: Medical Advisory Board: Cochlear Americas; Brain Westerberg: consultant, Surgeon’s Advisory Board: Cochlear Americas, consultant, Surgeon’s Advisory Board: Advanced Bionics Corp. Reprint requests: Thomas J. Balkany, MD, University of Miami Ear Institute, Department of Otolaryngology, PO Box 016960 (D48) Miami, FL 33101. E-mail address: [email protected].
0194-5998/$32.00 © 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved. doi:10.1016/j.otohns.2007.01.006
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Table 1 Coinvestigator group Institution
Principal investigator
California Ear Institute Dallas Otolaryngology Association House Ear Institute Mayo Clinic – Rochester New York University Oregon Health Science Center Ottawa Hospital, Civic Campus Rocky Mountain Ear Center St Paul’s Hospital, Vancouver University of Iowa University of Miami University of Michigan University of North Carolina Washington University
J. Roberson R. Peters W. Luxford C. Driscoll S. Waltzman S. McMenomy D. Schramm D. Kelsall B. Westerberg B. Gantz T. Balkany S. Tellian H. Pillsbury J. Gail Neely
the United States and Canada (Table 1) and was part of Food and Drug Administration clinical trial #G040122. It complied with all international guidelines for human subjects research, and all centers obtained individual institutional review board approval (Clinical Ethics Review Board approval in Canada) before beginning the study. The objective of this study was to measure speech perception with this device including a comparison of different stimulation rates. Secondarily, speech perception results in this group of patients were compared with a similar group receiving the Nucleus Contour device.
METHODS Subjects All subjects were 18 years of age or older; postlinguistically severely to profoundly hearing impaired; spoke English as their primary language; and had no indication of cochlear dysplasia or ossification, retrocochlear hearing impairment, or major psychological disorder. Speech criteria included aided Hearing in Noise Test (HINT)-Q sentence scores 50% in the ear to be implanted and ⱕ60% in the best aided (usually binaural) condition or CNC word scores of ⱕ30% aided at 60 dB SPL. Seventy-one subjects were enrolled into the study between July 2004 and December 2005. Fifty-five subjects who had completed six months in the study comprised the subject population.
Protocol The study was conducted as a within-subject repeated measures experiment (in which each subject served as his or her own control) to accommodate the heterogeneity that is well known to characterize hearing-impaired populations. Blinding or masking procedures were not included in the design for preoperative versus postoperative comparisons because
the presence or absence of a cochlear implant is not easily concealed from device recipients and/or clinical investigators. To minimize a test-order effect, each subject was exposed to and tested sequentially in each strategy using an A¡B¡A¡B¡Preferred Strategy order. As part of the Food and Drug Administration approval conditions, an additional evaluation point was added to the study for 12 months post initial activation. During the investigation, subjects used two strategies, ACE and ACE RE, with three rates in each strategy. The ACE strategy contained the frequencies 500, 900, and 1,200 Hz, and the ACE RE strategy contained the frequencies 1,800, 2,400, and 3,500 Hz. The order in which subjects were allocated to begin the study with ACE or ACE RE was randomized, and subjects were blinded to both the order and strategy assigned. Approximately one month postoperatively, subjects were fit with either ACE or ACE RE (termed the subject’s “strategy 1”). Because of the complexity and long duration of the study, the 3-week interval was chosen as a matter of practicality. In addition to the 3-week intervals, study subjects used programs with their preferred ACE as well as their preferred ACE RE map for six weeks before choosing their overall preferred rate. During the first three weeks, the subject used three different rates of stimulation within strategy 1. At the end of three weeks, the subject selected a preferred rate within strategy 1, used only that rate for two weeks, and was tested at week 5. After testing at week 5, subjects were switched to strategy 2. Again, during the first three weeks, the subjects experienced three different rates within strategy 2 and selected their preferred rate at week 8. They then used only their preferred rate for two weeks at which time strategy 1 was refitted and both preferred rates for strategy 1 and for strategy 2 were used for two more weeks. Subjects were instructed to use both rates and compare them during those two weeks. At week 12, both were tested. Further fitting and testing was performed at week 14, and at week 16 the subjects made a final determination of their preferred rate. The preferred rate remained the subject’s choice through the end of the study. Table 2 describes the actual testing sched-
Table 2 Testing protocol 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
1 month postop Week 3 Week 5 Week 8 Week 10 Week 12 Week 14 Week 16 Week 24 Week 48
Fit strategy #1 Identify preferred rate Test strategy #1/fit strategy #2 Identify preferred rate Fit strategy #1 Test both strategies/fit strategy #2 Test both & fit both strategies Fit preferred strategy Test preferred strategy Test preferred strategy
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Table 3 Subject demographics North American Clinical Trial Subject demographics (N ⫽ 71) Age at implant Age at onset of HL Duration of HL Duration of SP SNHL Preop CNC 60 dB Preop HINT(Q)
Mean
Range (y)
61 y 24 y 34 y 12 y 3% 11.30%
(23-90) (0.5-75) (0.8-74) (0.5-61) (0%-19%) (0%-55.7%)
ule. Note that the preferred strategy is tested at six months and 12 months.
Audiometric Testing All pre- and postimplantation audiometric testing was performed by using audiometers calibrated to American National Standards Institute standards with maximum output for frequencies 0.25 to 4 kHz less than 120 decibels hearing level (dB HL). Testing was performed in a sound-treated booth with insert earphones for unaided testing or a speaker for hearing aid and CI evaluations. Baseline audiograms were obtained at the time of the patients’ initial preimplant evaluation. Responses to pure tones 0.25 to 8 k HZ as well as open-set word and sentence recognition were measured for each ear in the aided and unaided conditions. For postoperative speech testing, subjects were seated in a sound-treated booth with CI adjusted to user’s most comfortable listening setting. Speech stimuli were presented via speaker at 0 degree azimuth with the subject seated 1 to 1.5 meters from the speaker. All speech testing was performed by using compact disk recordings. The following measures of speech perception were tested on all subjects: HINT sentences in quiet at 60 dB SPL, CNC words/phonemes in quiet 60 dB and 70 dB SPL, HINT sentences in noise 60 dB SPL SNR 10 dB, and City University of New York sentences in noise 70 dB SPL SNR 10 dB.2-4
Figure 1 Distribution of pre-operative speech perception using HINT-Q sentences at 70dB SPL.
759
Table 4 Speech perception results in preferred condition at 6 months
HINT(Q) HINT(N) CNC (70 dB)
Mean (%)
Median (%)
Range (%)
SD (%)
78.2 64 57.4
88.5 68 66
15.8-100 2.7-99 3-92
24.9 29.2 26.8
Comparison With Nucleus Contour CNC Word Recognition Scores CNC word recognition scores from this study were compared with those of patients receiving a predecessor device from the same manufacturer, the Nucleus Contour with Sprint or Esprit processor and ACE programming strategy.
Surgical Technique All surgery was performed by experienced CI surgeons using a manufacturer-approved technique. A postauricular incision was carried to the level of the temporalis fascia/ pericranium. An anteriorly based temporalis/pericranial flap was then developed. A seat for the receiver stimulator and
Figure 2
Preferred rates of stimulation by patients.
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complete mastoidectomy were performed and the facial recess opened. Hemostasis was obtained, and the area copiously irrigated. A cochleostomy was created anteroinferior to the round window membrane. The receiver/stimulator was then inserted into its subpericranial pocket, seated, and secured with sutures. The electrode was then placed via the posterior tympanotomy and cochleostomy into scala tympani using the advance off-stylet technique (in most instances). The wound was copiously irrigated, the incision was closed, and a mastoid dressing was applied.
Statistical Analysis Subjective choices of stimulation rate were analyzed by the nonparametric binomial test. The binomial test procedure was to compare the observed frequencies of ACE rates and ACE RE rates. Differences in CNC word scores for contour and freedom (see Discussion) were analyzed by t test. A statistical package, SPSS Inc, Chicago, IL, was used for the binomial test and Sigma Stat by SyStat Software Inc, Richmond, CA, was used for CNC word score comparisons.
Role of Sponsor Two coauthors of this article are employees of the sponsor, Cochlear Americas (Denver, CO), and played central roles in study design, data collection, and analysis. They also played secondary roles in interpretation of the data and
Figure 3
writing the report but not in the decision to submit the article for publication.
RESULTS Fifty-five subjects have at least six months of use with their Nucleus Freedom devices. Seven of the original 71 subjects withdrew from the study for a variety of reasons unrelated to their CI (eg, unable to return for frequent testing), and nine had not completed the six month testing protocol at the time of writing. The average age at implantation was 62 (range, 23-90) years with an average age of onset of hearing loss at 24 (range, 1-75) years of age. The duration of hearing loss was 33 (range, 1-74) years, and the mean duration of severe to profound sensorineural hearing loss was 12 (range, 1-61) years. The subject demographics can be found in Table 3. Figure 1 displays a wide distribution of preoperative HINT-Q Sentence scores by subjects for the implant ear. The mean preoperative HINT-Q Sentence score at 70 dB SPL was 11.3 % (SD ⫽ 25.6%). The mean preoperative CNC Word score at 60 dB SPL was 3.0 % (SD ⫽ 8.3%). Over 40% had no open set sentence recognition preoperatively, and only four subjects scored above 30% on HINT-Q sentences. Table 4 shows the overall postoperative speech perception results at six months tested in the patient’s preferred
Individual subjects CNC word scores, HINT-N sentences (and means) at preferred stimulation rates (week 24).
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Nucleus freedom North American clinical trial
strategy. On CNC words, the mean score is 57%, HINT Sentences in Quiet 78%, and HINT Sentences in Noise 64%. The ABAB design was chosen to minimize a learning or adjustment effect that may occur over time. In this study, both A and B strategies were associated with results that improved over time, but statistical analysis showed that the better performing strategy was significantly better than the other at all stages of the study. Preferred rates chosen by individual subjects tended toward the slower options within each of the two strategies. Furthermore, 37 of 55 subjects chose the slower rates in ACE over the faster rates in ACE RE. A binomial test was run, and the choice of ACE rates over ACE RE rates is statistically significant (binomial test, .014a). Figure 2 shows the subjective choice of stimulation rate by number of subjects. Figure 3 shows the individual score for CNC words and HINT-N across the various rates. A wide range of performance is seen at each of the six stimulation rates chosen by subjects. There are no
761
significant performance differences in speech perception associated with the rate of stimulation.
DISCUSSION Although the improvement in CI performance noted over the past decade is usually attributed to technical innovation, it may also be caused in part by favorable characteristics of CI recipients such as shorter terms of deafness, more residual hearing, or younger age. To address the concern that improved performance, if any, may be caused by subject characteristics rather than device enhancements, we analyzed characteristics of the subject group that may be associated with performance. The patient demographics of this study (average age at implantation 62 years, duration of severe to profound HL 12
Table 5 Speech perception scores week 12 ACE and ACE RE Subject number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Preferred rate week 24 (Hz)
CNC word scores 60 dB ACE (week 12) (%)
CNC word scores 60 dB ACE RE (week 12) (%)
HINT(N) 60 dB ACE (week 12) (%)
HINT(N) 60 dB ACE RE (week 12) (%)
900 1800 1800 900 500 900 2400 500 3500 1200 500 1200 900 500 500 1800 1200 500 1800 900 1200 1800 500 1800 2400 500 500 2400 500 1200 1800 500 500 1800 1800 1800
75 25 16 46 2 82 53 69 43 47 61 71 46 24 29 7 20 67 47 21 62 35 46 44 65 82 19 55 35 63 80 75 10 14 70 51
69 48 20 52 2 79 65 74 60 41 66 80 33 26 14 10 20 52 54 18 54 37 26 38 73 72 10 63 23 64 60 66 8 24 74 43
84.8 57.8 39.7 88.4 7.5 96.3 54.4 90.6 43.0 49.1 83.2 69.6 49.3 17.8 21.5 8.6 26.6 90.6 50.7 20.9 93.3 51.4 67.2 57.5 82.1 94.1 28.2 43.4 60.0 62.3 90.6 91.5 12.3 25.8 85.3 76.8
84.9 73.9 29.4 83.7 3.9 94.4 67.6 93.5 62.9 40.0 60.4 71.9 31.7 26.9 7.6 8.4 32.4 91.0 59.8 15.3 89.6 59.3 71.0 51.3 87.6 73.2 0.0 85.2 20.8 41.5 68.4 86.1 23.4 12.5 92.3 63.6
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years) are very similar to those of the previous generation Nucleus Contour study (n ⫽ 56; average age at implantation 59.9 years; duration of severe to profound HL 10.9 years).5 Over 40% of subjects had no open-set speech recognition preoperatively. On HINT-Q sentences, nearly 60% scored ⱕ10%, and only four subjects scored above 30%. We interpret these findings to mean that the subject group does not have inherent characteristics that would tend to produce better outcomes. In overall choices of stimulation rate, subjects tended to prefer slower rates. Sixty-seven percent preferred slower rates of stimulation, and their preference indicated higher speech perception scores in their preferred rates. In a few instances, subject preference was higher in their nonpreferred rate. Faster rates of stimulation did not necessarily produce higher speech perception scores. Comparison of speech perception scores on the 55 subjects can be viewed in Table 5. A variety of rates were preferred by the group indicating value in providing flexibility of programming. Performance on measures of speech perception is highly variable and not related to rate of stimulation. Nonetheless, it should be emphasized that failure of increased stimulation rate to improve hearing outcomes in this study is specific to this device. Prior studies have indicated that under different circumstances, higher rate stimulation may be beneficial. For example, Nie et al6 showed improved speech recognition in noise in 5 MedEl (Innsbruck, Austria) recipients that may be related to higher frequency perception. However, Friesen et al7 showed no significant change in performance as a function of stimulation rate in Clarion C1, Clarion C2, or Nucleus 24 recipients and suggested that CI recipients may not be able to access temporal cues made possible by high stimulation rates, a conclusion supported by Galvin and Fu.8 Speech perception results with this device are higher than seen with the prior generation Contour device for CNC words. CNC word score in quiet was 57.4% (SD 26.8%) with Freedom and 47% (SD 18.5%) with data from 26 of the Contour Clinical Trial subjects. CNC word scores were presented at the same level for Contour and Freedom subjects. This difference is significant (P ⫽ 0.012). It should be noted that different presentation levels were used for HINT-Q sentences in the Contour (70 dB) and Freedom (60 dB) studies. For that reason, direct comparisons are not possible for
HINT-Q sentences. Direct comparisons with devices from other manufacturers are similarly confounded by variability in testing and reporting protocols.
CONCLUSIONS A variety of stimulation rates between 500 and 3500 Hz was chosen by subjects of this study. However, the majority of subjects chose the slower strategy (ACE) over the faster research strategy (ACE RE). Furthermore, the majority chose the slowest rate within each strategy. Thus, faster is not necessarily better for cochlear implant stimulation with this device. Nonetheless, these findings cannot be generalized to other devices or processing strategies. CNC word recognition with the Freedom device is superior to that achieved with the previous-generation Contour device. Review of demographic data suggests that this improvement is not a result of characteristics of the two recipient groups and may be attributed to device improvement. The authors would like to acknowledge the dedication and efforts put forth by the audiologists (co-investigators) at the 14 clinical trial sites.
REFERENCES 1. Balkany TJ, Hodges AV, Eshraghi AA, et al. Cochlear implants in children. Acta Otolaryngol 2002;122:356 – 62. 2. Peterson FE, Lehiste I. Revised CNC lists for auditory tests. J Speech Hear Disord 1962;27:62–70. 3. Boothroyd A, Nittrouer S. Mathematical treatment of context effects in phoneme and word recognition. J Acoust Soc Am 1988;84:101–14. 4. Nilsson M, Soli SD, Sullivan J. Development of the hearing in noise test for the measurement of speech reception thresholds in quiet and in noise. J Acoust Soc Am 1994;95:1085–99. 5. Parkinson AJ, et al. The nucleus 24 contour cochlear implant system: Adult clinical trial results. Ear Hear 2002;23(1 Suppl):41S– 8. 6. Nie K, Barco A, Zeng FG. Spectral and temporal cues in cochlear implant speech perception. Ear Hear 2006;27:208 –17. 7. Friesen LM, Shannon RV, Cruz RJ. Effects of stimulation rate on speech recognition with cochlear implants. Audiol Neurootol 2005;10: 169 – 84. 8. Galvin JJ, Fu QJ. Effects of stimulation rate, mode and level on modulation detection by cochlear implant users. J Assoc Res Otolaryngol 2005;6:269 –79.
ORIGINAL RESEARCH
Nucleus Freedom North American clinical trial Thomas Balkany, MD, Annelle Hodges, PhD, Christine Menapace, MA, Linda Hazard, MS, Colin Driscoll, MD, Bruce Gantz, MD, David Kelsall, MD, William Luxford, MD, Sean McMenomy, MD, J. Gail Neely, MD, Brian Peters, MD, Harold Pillsbury, MD, Joseph Roberson, MD, David Schramm, MD, Steven Telian, MD, Susan Waltzman, PhD, Brian Westerberg, MD, and Stacy Payne, MS, Rochester, and New York, NY; Jacksonville and Miami, FL OBJECTIVE: To evaluate hearing outcomes and effects of stimulation rate on performance with the Nucleus Freedom cochlear implant (Cochlear Americas, Denver, CO). STUDY DESIGN AND SETTING: Randomized, controlled, prospective, single-blind clinical study using single-subject repeated measures (A-B-A-B) design at 14 academic centers in the United States and Canada and comparison with outcomes of a prior device by the same manufacturer. PATIENTS: Seventy-one severely/profoundly hearing impaired adults. RESULTS: Seventy-one adult recipients were randomly programmed in two different sets of rate: ACE or higher rate ACE RE. Mean scores for Consonant Nucleus Consonant words is 57%, Hearing in Noise Test (HINT) sentences in quiet 78%, and HINT sentences in noise 64%. Sixty-seven percent of subjects preferred slower rates of stimulation, and performance did not improve with higher rates of stimulation using this device. CONCLUSIONS: Subjects performed well, and there was no advantage to higher stimulation rates with this device. From the University of Miami Ear Institute, Miami, FL (Drs Balkany and Hodges); Cochlear Americas, Denver, CO (Drs Menapace and Hazard); Mayo Clinic Rochester, Rochester, MN (Dr Driscoll); University of Iowa, Iowa City, IA (Dr Gantz); Rocky Mountain Ear Center, Denver, CO (Dr Kelsall); House Ear Clinic, Los Angeles, CA (Dr Luxford); Oregon Health Science Center, Portland, OR (Dr McMenomy); Washington University, St. Louis, MO (Dr Neely); Dallas Otolaryngology Association, Dallas, TX (Dr Peters); University of North Carolina, Chapel Hill, NC (Dr Pillsbury); California Ear Institute, Palo Alto, CA (Dr Roberson); Ottawa Hospital, Civic Campus, Ottawa, Ontario (Dr Schramm); University of Michigan, Ann Arbor, MI (Dr Telian); New York University, New York, NY (Dr Waltzman); St. Paul’s Hospital, Vancouver, BC (Dr Westerberg); and Nemours Clinic Jacksonville (Dr Payne). Disclosures: Thomas Balkany: consultant: Cochlear Americas, Advanced Bionics, Med EL Corporation; Christine Menapace: employee: Cochlear Ameri-
SIGNIFICANCE: Higher stimulation rates do not necessarily result in improved performance. © 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved.
C
ochlear implant (CI) outcomes have improved over the past 10 years,1 and much of this progress may be attributable to the development of more sophisticated CI technology. The 6-month data reported here are from a multicenter, prospective, randomized clinical trial designed to evaluate performance aspects of the Nucleus Freedom CI and include effects of stimulation rate on speech recognition. This device was introduced into clinical trials in North America in June of 2004 and incorporated a number of putative technological improvements to its predecessor, the Nucleus 24 Contour. Among these changes, the newer receiver stimulator is capable of faster rate speech-processing strategies. This study was performed at 14 experienced centers in
cas; Linda Hazard: employee: Cochlear Americas, Principal Clinical Studies Specialist; Colin Driscoll: consultant: Cochlear Americas; Bruce Gantz: consultant: Medtronics, Ansbach; David Kelsall: consultant/Speaker’s Bureau: Cochlear Americas, William Luxford: consultant/Speakers Bureau: Cochlear Americas, M. Cochlear Corp and Advanced Bionics, Medical Advisory Board; Sean McMenomy: Medical Advisory Board: Cochlear Americas; Joseph Roberson: consultant/Medical Advisory Board: Cochlear Americas, consultant: Acclarent/ Medtronic, NeuroPace; Steven Telian: Medical Advisory Board: Cochlear Americas; Brain Westerberg: consultant, Surgeon’s Advisory Board: Cochlear Americas, consultant, Surgeon’s Advisory Board: Advanced Bionics Corp. Reprint requests: Thomas J. Balkany, MD, University of Miami Ear Institute, Department of Otolaryngology, PO Box 016960 (D48) Miami, FL 33101. E-mail address: [email protected].
0194-5998/$32.00 © 2007 American Academy of Otolaryngology–Head and Neck Surgery Foundation. All rights reserved. doi:10.1016/j.otohns.2007.01.006
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Table 1 Coinvestigator group Institution
Principal investigator
California Ear Institute Dallas Otolaryngology Association House Ear Institute Mayo Clinic – Rochester New York University Oregon Health Science Center Ottawa Hospital, Civic Campus Rocky Mountain Ear Center St Paul’s Hospital, Vancouver University of Iowa University of Miami University of Michigan University of North Carolina Washington University
J. Roberson R. Peters W. Luxford C. Driscoll S. Waltzman S. McMenomy D. Schramm D. Kelsall B. Westerberg B. Gantz T. Balkany S. Tellian H. Pillsbury J. Gail Neely
the United States and Canada (Table 1) and was part of Food and Drug Administration clinical trial #G040122. It complied with all international guidelines for human subjects research, and all centers obtained individual institutional review board approval (Clinical Ethics Review Board approval in Canada) before beginning the study. The objective of this study was to measure speech perception with this device including a comparison of different stimulation rates. Secondarily, speech perception results in this group of patients were compared with a similar group receiving the Nucleus Contour device.
METHODS Subjects All subjects were 18 years of age or older; postlinguistically severely to profoundly hearing impaired; spoke English as their primary language; and had no indication of cochlear dysplasia or ossification, retrocochlear hearing impairment, or major psychological disorder. Speech criteria included aided Hearing in Noise Test (HINT)-Q sentence scores 50% in the ear to be implanted and ⱕ60% in the best aided (usually binaural) condition or CNC word scores of ⱕ30% aided at 60 dB SPL. Seventy-one subjects were enrolled into the study between July 2004 and December 2005. Fifty-five subjects who had completed six months in the study comprised the subject population.
Protocol The study was conducted as a within-subject repeated measures experiment (in which each subject served as his or her own control) to accommodate the heterogeneity that is well known to characterize hearing-impaired populations. Blinding or masking procedures were not included in the design for preoperative versus postoperative comparisons because
the presence or absence of a cochlear implant is not easily concealed from device recipients and/or clinical investigators. To minimize a test-order effect, each subject was exposed to and tested sequentially in each strategy using an A¡B¡A¡B¡Preferred Strategy order. As part of the Food and Drug Administration approval conditions, an additional evaluation point was added to the study for 12 months post initial activation. During the investigation, subjects used two strategies, ACE and ACE RE, with three rates in each strategy. The ACE strategy contained the frequencies 500, 900, and 1,200 Hz, and the ACE RE strategy contained the frequencies 1,800, 2,400, and 3,500 Hz. The order in which subjects were allocated to begin the study with ACE or ACE RE was randomized, and subjects were blinded to both the order and strategy assigned. Approximately one month postoperatively, subjects were fit with either ACE or ACE RE (termed the subject’s “strategy 1”). Because of the complexity and long duration of the study, the 3-week interval was chosen as a matter of practicality. In addition to the 3-week intervals, study subjects used programs with their preferred ACE as well as their preferred ACE RE map for six weeks before choosing their overall preferred rate. During the first three weeks, the subject used three different rates of stimulation within strategy 1. At the end of three weeks, the subject selected a preferred rate within strategy 1, used only that rate for two weeks, and was tested at week 5. After testing at week 5, subjects were switched to strategy 2. Again, during the first three weeks, the subjects experienced three different rates within strategy 2 and selected their preferred rate at week 8. They then used only their preferred rate for two weeks at which time strategy 1 was refitted and both preferred rates for strategy 1 and for strategy 2 were used for two more weeks. Subjects were instructed to use both rates and compare them during those two weeks. At week 12, both were tested. Further fitting and testing was performed at week 14, and at week 16 the subjects made a final determination of their preferred rate. The preferred rate remained the subject’s choice through the end of the study. Table 2 describes the actual testing sched-
Table 2 Testing protocol 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
1 month postop Week 3 Week 5 Week 8 Week 10 Week 12 Week 14 Week 16 Week 24 Week 48
Fit strategy #1 Identify preferred rate Test strategy #1/fit strategy #2 Identify preferred rate Fit strategy #1 Test both strategies/fit strategy #2 Test both & fit both strategies Fit preferred strategy Test preferred strategy Test preferred strategy
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Table 3 Subject demographics North American Clinical Trial Subject demographics (N ⫽ 71) Age at implant Age at onset of HL Duration of HL Duration of SP SNHL Preop CNC 60 dB Preop HINT(Q)
Mean
Range (y)
61 y 24 y 34 y 12 y 3% 11.30%
(23-90) (0.5-75) (0.8-74) (0.5-61) (0%-19%) (0%-55.7%)
ule. Note that the preferred strategy is tested at six months and 12 months.
Audiometric Testing All pre- and postimplantation audiometric testing was performed by using audiometers calibrated to American National Standards Institute standards with maximum output for frequencies 0.25 to 4 kHz less than 120 decibels hearing level (dB HL). Testing was performed in a sound-treated booth with insert earphones for unaided testing or a speaker for hearing aid and CI evaluations. Baseline audiograms were obtained at the time of the patients’ initial preimplant evaluation. Responses to pure tones 0.25 to 8 k HZ as well as open-set word and sentence recognition were measured for each ear in the aided and unaided conditions. For postoperative speech testing, subjects were seated in a sound-treated booth with CI adjusted to user’s most comfortable listening setting. Speech stimuli were presented via speaker at 0 degree azimuth with the subject seated 1 to 1.5 meters from the speaker. All speech testing was performed by using compact disk recordings. The following measures of speech perception were tested on all subjects: HINT sentences in quiet at 60 dB SPL, CNC words/phonemes in quiet 60 dB and 70 dB SPL, HINT sentences in noise 60 dB SPL SNR 10 dB, and City University of New York sentences in noise 70 dB SPL SNR 10 dB.2-4
Figure 1 Distribution of pre-operative speech perception using HINT-Q sentences at 70dB SPL.
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Table 4 Speech perception results in preferred condition at 6 months
HINT(Q) HINT(N) CNC (70 dB)
Mean (%)
Median (%)
Range (%)
SD (%)
78.2 64 57.4
88.5 68 66
15.8-100 2.7-99 3-92
24.9 29.2 26.8
Comparison With Nucleus Contour CNC Word Recognition Scores CNC word recognition scores from this study were compared with those of patients receiving a predecessor device from the same manufacturer, the Nucleus Contour with Sprint or Esprit processor and ACE programming strategy.
Surgical Technique All surgery was performed by experienced CI surgeons using a manufacturer-approved technique. A postauricular incision was carried to the level of the temporalis fascia/ pericranium. An anteriorly based temporalis/pericranial flap was then developed. A seat for the receiver stimulator and
Figure 2
Preferred rates of stimulation by patients.
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complete mastoidectomy were performed and the facial recess opened. Hemostasis was obtained, and the area copiously irrigated. A cochleostomy was created anteroinferior to the round window membrane. The receiver/stimulator was then inserted into its subpericranial pocket, seated, and secured with sutures. The electrode was then placed via the posterior tympanotomy and cochleostomy into scala tympani using the advance off-stylet technique (in most instances). The wound was copiously irrigated, the incision was closed, and a mastoid dressing was applied.
Statistical Analysis Subjective choices of stimulation rate were analyzed by the nonparametric binomial test. The binomial test procedure was to compare the observed frequencies of ACE rates and ACE RE rates. Differences in CNC word scores for contour and freedom (see Discussion) were analyzed by t test. A statistical package, SPSS Inc, Chicago, IL, was used for the binomial test and Sigma Stat by SyStat Software Inc, Richmond, CA, was used for CNC word score comparisons.
Role of Sponsor Two coauthors of this article are employees of the sponsor, Cochlear Americas (Denver, CO), and played central roles in study design, data collection, and analysis. They also played secondary roles in interpretation of the data and
Figure 3
writing the report but not in the decision to submit the article for publication.
RESULTS Fifty-five subjects have at least six months of use with their Nucleus Freedom devices. Seven of the original 71 subjects withdrew from the study for a variety of reasons unrelated to their CI (eg, unable to return for frequent testing), and nine had not completed the six month testing protocol at the time of writing. The average age at implantation was 62 (range, 23-90) years with an average age of onset of hearing loss at 24 (range, 1-75) years of age. The duration of hearing loss was 33 (range, 1-74) years, and the mean duration of severe to profound sensorineural hearing loss was 12 (range, 1-61) years. The subject demographics can be found in Table 3. Figure 1 displays a wide distribution of preoperative HINT-Q Sentence scores by subjects for the implant ear. The mean preoperative HINT-Q Sentence score at 70 dB SPL was 11.3 % (SD ⫽ 25.6%). The mean preoperative CNC Word score at 60 dB SPL was 3.0 % (SD ⫽ 8.3%). Over 40% had no open set sentence recognition preoperatively, and only four subjects scored above 30% on HINT-Q sentences. Table 4 shows the overall postoperative speech perception results at six months tested in the patient’s preferred
Individual subjects CNC word scores, HINT-N sentences (and means) at preferred stimulation rates (week 24).
Balkany et al
Nucleus freedom North American clinical trial
strategy. On CNC words, the mean score is 57%, HINT Sentences in Quiet 78%, and HINT Sentences in Noise 64%. The ABAB design was chosen to minimize a learning or adjustment effect that may occur over time. In this study, both A and B strategies were associated with results that improved over time, but statistical analysis showed that the better performing strategy was significantly better than the other at all stages of the study. Preferred rates chosen by individual subjects tended toward the slower options within each of the two strategies. Furthermore, 37 of 55 subjects chose the slower rates in ACE over the faster rates in ACE RE. A binomial test was run, and the choice of ACE rates over ACE RE rates is statistically significant (binomial test, .014a). Figure 2 shows the subjective choice of stimulation rate by number of subjects. Figure 3 shows the individual score for CNC words and HINT-N across the various rates. A wide range of performance is seen at each of the six stimulation rates chosen by subjects. There are no
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significant performance differences in speech perception associated with the rate of stimulation.
DISCUSSION Although the improvement in CI performance noted over the past decade is usually attributed to technical innovation, it may also be caused in part by favorable characteristics of CI recipients such as shorter terms of deafness, more residual hearing, or younger age. To address the concern that improved performance, if any, may be caused by subject characteristics rather than device enhancements, we analyzed characteristics of the subject group that may be associated with performance. The patient demographics of this study (average age at implantation 62 years, duration of severe to profound HL 12
Table 5 Speech perception scores week 12 ACE and ACE RE Subject number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
Preferred rate week 24 (Hz)
CNC word scores 60 dB ACE (week 12) (%)
CNC word scores 60 dB ACE RE (week 12) (%)
HINT(N) 60 dB ACE (week 12) (%)
HINT(N) 60 dB ACE RE (week 12) (%)
900 1800 1800 900 500 900 2400 500 3500 1200 500 1200 900 500 500 1800 1200 500 1800 900 1200 1800 500 1800 2400 500 500 2400 500 1200 1800 500 500 1800 1800 1800
75 25 16 46 2 82 53 69 43 47 61 71 46 24 29 7 20 67 47 21 62 35 46 44 65 82 19 55 35 63 80 75 10 14 70 51
69 48 20 52 2 79 65 74 60 41 66 80 33 26 14 10 20 52 54 18 54 37 26 38 73 72 10 63 23 64 60 66 8 24 74 43
84.8 57.8 39.7 88.4 7.5 96.3 54.4 90.6 43.0 49.1 83.2 69.6 49.3 17.8 21.5 8.6 26.6 90.6 50.7 20.9 93.3 51.4 67.2 57.5 82.1 94.1 28.2 43.4 60.0 62.3 90.6 91.5 12.3 25.8 85.3 76.8
84.9 73.9 29.4 83.7 3.9 94.4 67.6 93.5 62.9 40.0 60.4 71.9 31.7 26.9 7.6 8.4 32.4 91.0 59.8 15.3 89.6 59.3 71.0 51.3 87.6 73.2 0.0 85.2 20.8 41.5 68.4 86.1 23.4 12.5 92.3 63.6
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years) are very similar to those of the previous generation Nucleus Contour study (n ⫽ 56; average age at implantation 59.9 years; duration of severe to profound HL 10.9 years).5 Over 40% of subjects had no open-set speech recognition preoperatively. On HINT-Q sentences, nearly 60% scored ⱕ10%, and only four subjects scored above 30%. We interpret these findings to mean that the subject group does not have inherent characteristics that would tend to produce better outcomes. In overall choices of stimulation rate, subjects tended to prefer slower rates. Sixty-seven percent preferred slower rates of stimulation, and their preference indicated higher speech perception scores in their preferred rates. In a few instances, subject preference was higher in their nonpreferred rate. Faster rates of stimulation did not necessarily produce higher speech perception scores. Comparison of speech perception scores on the 55 subjects can be viewed in Table 5. A variety of rates were preferred by the group indicating value in providing flexibility of programming. Performance on measures of speech perception is highly variable and not related to rate of stimulation. Nonetheless, it should be emphasized that failure of increased stimulation rate to improve hearing outcomes in this study is specific to this device. Prior studies have indicated that under different circumstances, higher rate stimulation may be beneficial. For example, Nie et al6 showed improved speech recognition in noise in 5 MedEl (Innsbruck, Austria) recipients that may be related to higher frequency perception. However, Friesen et al7 showed no significant change in performance as a function of stimulation rate in Clarion C1, Clarion C2, or Nucleus 24 recipients and suggested that CI recipients may not be able to access temporal cues made possible by high stimulation rates, a conclusion supported by Galvin and Fu.8 Speech perception results with this device are higher than seen with the prior generation Contour device for CNC words. CNC word score in quiet was 57.4% (SD 26.8%) with Freedom and 47% (SD 18.5%) with data from 26 of the Contour Clinical Trial subjects. CNC word scores were presented at the same level for Contour and Freedom subjects. This difference is significant (P ⫽ 0.012). It should be noted that different presentation levels were used for HINT-Q sentences in the Contour (70 dB) and Freedom (60 dB) studies. For that reason, direct comparisons are not possible for
HINT-Q sentences. Direct comparisons with devices from other manufacturers are similarly confounded by variability in testing and reporting protocols.
CONCLUSIONS A variety of stimulation rates between 500 and 3500 Hz was chosen by subjects of this study. However, the majority of subjects chose the slower strategy (ACE) over the faster research strategy (ACE RE). Furthermore, the majority chose the slowest rate within each strategy. Thus, faster is not necessarily better for cochlear implant stimulation with this device. Nonetheless, these findings cannot be generalized to other devices or processing strategies. CNC word recognition with the Freedom device is superior to that achieved with the previous-generation Contour device. Review of demographic data suggests that this improvement is not a result of characteristics of the two recipient groups and may be attributed to device improvement. The authors would like to acknowledge the dedication and efforts put forth by the audiologists (co-investigators) at the 14 clinical trial sites.
REFERENCES 1. Balkany TJ, Hodges AV, Eshraghi AA, et al. Cochlear implants in children. Acta Otolaryngol 2002;122:356 – 62. 2. Peterson FE, Lehiste I. Revised CNC lists for auditory tests. J Speech Hear Disord 1962;27:62–70. 3. Boothroyd A, Nittrouer S. Mathematical treatment of context effects in phoneme and word recognition. J Acoust Soc Am 1988;84:101–14. 4. Nilsson M, Soli SD, Sullivan J. Development of the hearing in noise test for the measurement of speech reception thresholds in quiet and in noise. J Acoust Soc Am 1994;95:1085–99. 5. Parkinson AJ, et al. The nucleus 24 contour cochlear implant system: Adult clinical trial results. Ear Hear 2002;23(1 Suppl):41S– 8. 6. Nie K, Barco A, Zeng FG. Spectral and temporal cues in cochlear implant speech perception. Ear Hear 2006;27:208 –17. 7. Friesen LM, Shannon RV, Cruz RJ. Effects of stimulation rate on speech recognition with cochlear implants. Audiol Neurootol 2005;10: 169 – 84. 8. Galvin JJ, Fu QJ. Effects of stimulation rate, mode and level on modulation detection by cochlear implant users. J Assoc Res Otolaryngol 2005;6:269 –79.