Evaluating Speech Perception of the MAXUM Middle Ear Implant Versus Speech Perception Under Inserts

Transcription

1 The Laryngoscope VC 2017 The American Laryngological, Rhinological and Otological Society, Inc. Evaluating Speech Perception of the MAXUM Middle Ear Implant Versus Speech Perception Under Inserts R. Kent Dyer, MD; Michael Spearman, BS ; Brian Spearman, ME; Anna McCraney, AuD Objectives/Hypothesis: To evaluate the speech perception of the Ototronix MAXUM middle ear implant relative to the cochlear potential for speech perception of patients. Study Design: Clinical study chart review. Methods: We performed an evaluation of data from a prospective clinical study of 10 MAXUM patients. Primary outcome measures included comparison of word recognition (WR) scores with MAXUM (WR MAXUM ) versus word recognition under inserts (WR inserts ), and the functional gain improvement for pure-tone average (PTA) (0.5, 1, and 2 khz) and highfrequency pure-tone average (2, 3, and 4 khz). Results: Ten ears in 10 adult patients (six female; average age 68.7 years) were included. The average speech perception gap (difference between WR inserts and WR MAXUM ) with MAXUM was 29.2% (range, 226% to 4%). A negative number indicates that WR MAXUM was higher than the WR inserts. The average PTA with MAXUM was 23.1 db (range, db), a 38.0-dB gain over the preoperative unaided condition (range, db). The average high-frequency pure-tone average with MAXUM was 34.4 db (range, db), a 42.8-dB gain over the preoperative unaided condition (range, db). Conclusions: These data demonstrate that a significant, very strong correlation was observed between WR inserts and WR MAXUM scores (r , P 5.001), and a patient s WR inserts score may be used to reasonably predict the word recognition outcomes with MAXUM. Key Words: Middle ear implant, MAXUM, speech perception gap. Level of Evidence: 4. Laryngoscope, 128: , 2018 INTRODUCTION Improving speech understanding is the primary task of a hearing treatment device such as a hearing aid, middle ear implant (MEI) or cochlear implant. However, hearing aid benefit is limited by the amount of cochlear damage a patient may have that can be reliably characterized by PB max (maximum word recognition of phonetically balanced word list). 1 This is typically determined under inserts (earphones) or headphones. The effectiveness of a hearing aid at conversational speech can be evaluated by using monosyllabic words (i.e., Northwestern University Auditory Test No.6 [NU-6] or Consonant-Nucleus-Consonant [CNC]) at 60 to 65 db sound pressure level (SPL), 2 4 and CNC word testing has been added to the Minimum Speech Test Battery for cochlear implant candidacy. 4 Although PB max is the patient s cochlear potential to understand speech and From the Department of Surgery and on the Board of Directors at the Hough Ear Institute (R.K.D.), Oklahoma City, Oklahoma; and Ototronix LLC (M.S., B.S., A.M.), St. Paul, Minnesota, U.S.A. Editor s Note: This Manuscript was accepted for publication March 9, M.S. is CEO and shareholder at Ototronix. B.S. is Director of Clinical Research and Training, and a shareholder at Ototronix. A.M. is Director of Audiology at Ototronix. The authors have no other funding, financial relationships, or conflicts of interest to disclose. Send correspondence to R. Kent Dyer, MD, Department of Surgery and on the Board of Directors at the Hough Ear Institute, 3400 NW 56th Street, Oklahoma City, OK kdyeroto@gmail.com DOI: /lary should be considered as the individual s potential upper limit of hearing aid performance, it is not always an achievable goal. 3 However, there is poor correlation between aided word recognition scores (WRS) and word recognition under inserts (WR inserts ). 5 In one study, fewer than 40% of patients achieved aided WRS within 10% of their PB max with properly fit hearing aids, and the average across all patients was 20% below PB max, with some as much as 70% below. 3 In a Food and Drug Administration (FDA) clinical study for the MAXUM, patients were tested preoperatively for hearing aid performance prior to receiving the implant. An unexpected finding was that patients with nearly identical WR inserts had wide variations in aided WRS scores, even with optimally fit hearing aids. Variations from patient to patient as large as 60% were observed. These findings led to the conclusion that clinicians need to validate hearing aid performance by testing aided WRS rather than just using WR inserts and real-ear measurement (REM) verification to predict hearing aid benefit. 5 We have termed the difference between a patient s maximum speech perception and the speech perception scores using hearing treatment at conversational level speech (50 db HL or 60 db SPL) the Speech Perception gap (SP gap). The SP gap, therefore, represents the gap between the speech perception with treatment (SP treatment ) effectiveness and the patient s potential upper limit of speech perception (SP max ). It can be expressed as SP gap 5 SP max 2 SP treatment. In the case of using word recognition

2 Fig. 1. MAXUM middle ear implant utilizing an open-fit, completely-in-the-canal electromagnetic sound processor. (Courtesy of Ototronix, LLC) to determine speech perception, it can be expressed as: SP gap 5 PBmax WR treatment. The treatment could be hearing aids or MEIs. It is not entirely clear why an SP gap exists, and this should be investigated further. One of the possible reasons for some patients receiving limited benefit from hearing aids may be due to the inherent differences among patients in acoustic coupling between the speaker and the tympanic membrane, and the resulting differences in transmission of energy through the ossicular chain to the cochlea. Some patients have been shown to have this impaired middle ear transfer function that results in less movement of the ossicles with the same SPL input, resulting in up to 20-dB difference between patients. So, although the hearing aid is delivering the appropriate amount of acoustic energy at the eardrum for the level of hearing loss, the energy is not necessarily transferred the same through the eardrum and ossicles to the cochlea for all patients. 6 For patients with an impaired middle ear transfer function, an MEI has the advantage over acoustic hearing aids because direct driving of the ossicular chain, preferably as close to the cochlea as possible, bypasses the eardrum and ossicles where the dampening of energy occurs. 7 Another reason may be due to the inability of acoustic hearing aids to provide sufficient functional gain prior to feedback. This is especially noticeable in patients with moderately severe to severe high-frequency loss, where the lack of sufficient functional gain does not provide audibility of high-frequency sounds. Feedback cancellation algorithms and technology are used in hearing aids to increase the functional gain before feedback, but can have the undesirable side effect of generating some audible distortion in the process. 8 Distortion may reduce speech intelligibility. MEIs have been developed as another option for patients with hearing loss. These are typically used for patients with moderate to severe sensorineural loss, and particularly effective for patients with moderately severe to severe high-frequency loss. Rather than using acoustic energy to vibrate the eardrum and ossicles, MEIs directly drive the oval window using electromagnetic or piezoelectric drivers coupled to the ossicular chain. Acoustic feedback is virtually eliminated because there is no acoustic speaker. The external ear canal can be completely open, or a large vent may be used to prevent the occlusion effect. Furthermore, because the transducer directly drives the ossicles near the cochlea, signal degradation and distortion effects related to anatomical and physiological characteristics of the ear canal and tympanic membrane are reduced. 9 Several studies have demonstrated that functional gain and speech recognition improvement with MEIs is equivalent to or better than optimally fitted hearing aids, whereas patientperceived outcome measures show that active MEIs provide superior sound quality, reduced occlusion and feedback, and improved patient satisfaction The MAXUM system is a semi-implantable, electromagnetic MEI. It is FDA approved for moderate to severe sensorineural hearing loss with PB max scores of 60% or greater. It consists of a magnetic implant and an external integrated processor and coil (IPC) that is worn deep in the ear canal (Fig. 1). Although previous studies have reported outcomes comparing aided WRS to PB max or WR inserts, 1,2,5 there have not been any studies comparing the word recognition scores of MAXUM or any other MEI to PB max or WR inserts. This is the first study to characterize outcomes of the word recognition scores obtained with the MAXUM to WR inserts. MATERIALS AND METHODS Data from a prospective clinical study of the MAXUM digital IPC were evaluated. For the purposes of the present study, primary outcome measures included the correlation between word recognition scores with the MAXUM versus WR inserts, and the functional gain of the MAXUM relative to the unaided TABLE I. Summary of Demographic and Hearing Loss Information (N 5 10). Attribute Mean 6 SD or No. Age, yr Gender Female 6 Male 4 Duration of hearing loss, yr Etiology of hearing loss Unknown 8 Heredity 1 Congenital 1 Total time wearing hearing devices, yr Hearing device use Binaural 9 Monaural 1 Device used prior to study Hearing aid 4 Soundtec analog IPC 6 Study ear Left 5 Right 5 IPC 5 integrated processor and coil; SD 5 standard deviation. 457

3 reception threshold (SRT) 140 db. In the Soundtec analog IPC condition, pure-tone air-conduction thresholds were obtained, as well as word recognition in quiet in soundfield using NU-6 word lists at 50 db HL. The contralateral ear was plugged for all testing. Patients were then fitted with the MAXUM digital IPC, and each patient received between one and three postoperative visits for fitting adjustments as needed. Approximately 1 month following the MAXUM digital IPC activation, postoperative audiometric testing was completed under the same conditions described above. Fig. 2. Individual unaided air-conduction thresholds. condition under inserts for pure-tone average (PTA) and highfrequency pure-tone average (HFPTA). Following institutional review board approval, a clinical evaluation was conducted to show the safety and efficacy of a digital IPC compared to the outcomes of the original Soundtec analog IPC in the MAXUM system (formerly Soundtec Direct). Ten patients who had previously been implanted with the MAXUM system using a Soundtec analog IPC were enrolled in the study. All patients had normal middle ear function with no history of chronic or recurring middle ear pathology. The study took place between December 2009 and March The demographics for these patients is summarized in Table I. With the subjects acting as their own controls, preoperative audiometric testing was completed for the unaided and Soundtec analog IPC conditions in a sound booth. Nine of 10 of the patients had been implanted during the original FDA clinical study approximately 10 years earlier. The tenth patient was implanted shortly after FDA approval in For much of the period between the time of implantation and the digital processor study in 2010, Soundtec had limited support, and four of the patients lost or damaged their original IPC and went back to wearing hearing aids. For patients who had not been wearing their Soundtec analog IPC, they were fitted with a new one. In the unaided condition, pure-tone air- and bone-conduction thresholds were obtained, as well as unaided WR inserts earphones using NU-6 word lists at presentation levels of speech RESULTS The individual audiograms of the patients in the study are shown in Figure 2. The average unaided preoperative PTA was 61.2 db (range, db, median 65.8 db). The average PTA with the Soundtec analog IPC was 27.5 db (range, db, median 27.7 db), a 33.7-dB gain over the unaided condition. The average PTA with the MAXUM digital IPC was 23.1 db (range, db, median 21.3 db), a 38.1-dB gain over the unaided condition. The average unaided preoperative HFPTA was 77.2 db (range, db, median 81.7 db). The average HFPTA with the Soundtec analog IPC was 36.5 db (range, db, median 36 db), a 40.7-dB gain over the unaided condition. The average HFPTA with the MAXUM digital IPC was 34.4 db (range, db, median 34 db), a db gain over the unaided condition. Increases in gain were seen at all frequencies over the unaided condition with both the Soundtec analog and MAXUM digital IPCs. The aided thresholds for the MAXUM digital IPC were equivalent or slightly better than the Soundtec analog IPC at all frequencies (Table II and Fig. 3). The average unaided WR inserts score was 64.4% (range, 32% 84%; median 66%). The average word recognition score with the Soundtec analog IPC was 62.2% (range, 18% 84%; median 65%), a 2.2% (standard deviation [SD] 13.7%) difference below the average WR inserts. The average word recognition score with the MAXUM digital IPC was 73.6% (range, 32% 94%; median 76%), a 9.2% (SD 8.7%) difference above the WR inserts average (Table III). All 10 of the MAXUM digital IPC patients (100%) achieved word recognition scores within at least 10% of their WR inserts (SP gap of <10%). Nine of the 10 analog IPC patients (90%) achieved word recognition scores within 10% of their WR inserts score. Figure 4 shows the word recognition scores of the MAXUM digital IPC and Soundtec analog IPC plotted against WR inserts. It is apparent that the dots are closely TABLE II. Average Thresholds for Unaided, Soundtec Analog IPC, and MAXUM Digital IPC. Frequency, Hz ,000 2,000 3,000 4,000 6,000 8,000 PTA (0.5, 1, 2 khz) HFPTA (2, 3, 4 khz) Unaided Analog IPC Digital IPC HFPTA 5 high-frequency pure-tone average; IPC 5 integrated processor and coil device; PTA 5 pure-tone average. 458

4 Fig. 3. Average thresholds for unaided Soundtec analog IPC and MAXUM digital IPC. IPC 5 integrated processor and coil. aligned around the equivalence line for both the digital and analog IPCs. A significant, very strong correlation was observed between WR inserts and MAXUM digital IPC word recognition scores (r ; P 5.001). In addition, a significant, strong correlation was observed between WR inserts and Soundtec analog IPC word recognition scores (r ; P 5.017). The data also indicate improvements in average word recognition scores of 11.8% words correct using the MAXUM digital IPC device over the Soundtec analog IPC device. The improvement in NU-6 scores between devices is statistically significant (P ). DISCUSSION This is the first study to report the comparisons between word recognition scores with the MAXUM MEI and WR inserts. Whereas hearing aids have wide and Fig. 4. MAXUM and Soundtec WRS versus WR inserts. SRT 5 speech reception threshold; WRS, word recognition score; WR inserts, word recognition under inserts. varying outcomes in word recognition scores compared to WR inserts, 2,3,5 the MAXUM MEI showed consistent outcomes with a significant, very strong correlation to WR inserts. This is of significant interest, as the data show the WR inserts of a patient can reliably predict the word recognition scores outcome with MAXUM. This can provide a distinct advantage in treating hearing loss and recommending the most effective treatment option for a patient. For instance, if a patient achieves aided word recognition scores that are close to WR inserts, then the patient is receiving good benefit from the aids. However, if a patient does not achieve aided WRSs that are close to WR inserts, then the patient has a SP gap, and the potential exists for improvement with MAXUM. TABLE III. Individual Word Recognition Scores: WR inserts, Soundtec Analog, and MAXUM Digital Processors. Patient No Average WR inserts * 32% 84% 60% 48% 76% 80% 60% 64% 72% 68% 64.4% WRS, analog 52% 84% 60% 12% 78% 78% 60% 66% 68% 64% 62.2% WRS, digital 50% 88% 64% 44% 84% 94% 86% 76% 74% 76% 73.6% SP gap, analog 220% 0% 0% 136% 22% 12% 0% 22% 14% 14% 2.2% SP gap, digital 218% 24% 24% 14% 26% 214% 226% 212% 22% 28% 29.2% *Unaided WRS under inserts at SRT 140 db. WRS in soundfield at 50 db HL. SP gap 5 WR inserts WR MAXUM/Soundtec at 50 db HL. A negative SP gap score indicates WR MAXUM/Soundtec was better than WR inserts. SP 5 speech perception; SRT 5 speech reception threshold; WR inserts 5 word recognition under inserts; WR MAXUM/Soundtec 5 word recognition with MAXUM/Soundtec; WRS 5 word recognition score. 459

5 Furthermore, the extent of potential improvement can be calculated preoperatively by the SP gap. Our belief is that an SP gap of >18% should be considered significant based on Thornton-Raffin criteria. 18,19 Several strengths and limitations deserve mention. This is the first study to report on the correlation between word recognition scores with MAXUM and WR inserts.it also introduces the SP gap as a tool that provides an objective and clinically practical metric for evaluating treatment effectiveness versus a patient s cochlear potential. A limitation of this study may be the use of SRT 140 db as the presentation level. As stated earlier, PB max should be considered as the individual s potential upper limit of hearing aid performance, 3 yet several patients in this study exceeded their WR inserts scores with the MAXUM MEI, three by more than 10%. Although using an SRT 140 db presentation level has been a common clinical practice for estimating PB max, this does not always provide a patient s true PB max, or maximum cochlear potential, especially in moderately severe to severe and ski sloping patients. 18 Using SRT 140 could have underestimated the maximum word recognition potential of some of these patients. The best approach to speech recognition testing is to complete a performanceintensity function by presenting stimuli over a range of presentation levels, or at 5 db below the patient s Uncomfortable Loudness Level (UCL-5) when using a single presentation level. 21 The primary limitations of this study include the nature of its retrospective analysis, the limited number of subjects, and the use of SRT 140 db as a presentation level. Future studies with a larger cohort of patients should be considered to confirm these promising results. CONCLUSION The goal is for patients to reach their full potential regardless of whether they are using a hearing aid or one of the varieties of implants. The data reported here demonstrate that the word recognition scores with the MAXUM MEI are highly correlated to WR inserts scores, and a patient s WR inserts score may be used to reasonably predict the word recognition scores outcomes with the MAXUM implant. BIBLIOGRAPHY 1. Halpin, C, Rauch, SD. Clinical Implications of a damaged cochlea: pure tone-thresholds vs information carrying capacity. Otolaryngol Head Neck Surg 2008;140: Hoppe U, Hast A, Hocke T. Speech perception with hearing aids in comparison to pure-tone hearing loss [in German]. HNO 2014;62: Hoppe U, Hast A, Hocke T. CI candidacy audiometry-based screening procedure. Otol Neurotol 2015;36: Minimum speech test battery for adult cochlear implant users. Version 1.0. June Available at: MSTBfiles/MSTBManual %20.pdf 5. McRackan T, Ahlstrom J, Clinkscales W, Meyer T, Dubno J. Clinical implications of word recognition differences in earphone and aided conditions. Otol Neurotol 2016;37: Goode RL. The history and development of the implantable hearing aid. Otolaryngol Clin North Am 1995;28: Deveze A, Kokay K, Tringali S, Jenkins H, Tollin D. Techniques to improve the efficiency of a middle ear implant: effect of different methods of coupling to the ossicular chain. Otol Neurotol 2012;34: Ross M. Feedback cancellation systems and open-ear hearing aid fitting. Hear Loss Boeheim K, Pok SM, Schloegel M, Filzmoser P. Active middle ear implant compared with open-fit hearing aid in sloping high-frequency sensorineural hearing loss. Otol Neurotol 2010;31: Hunter J, Carlson M, Glasscock ME. The Ototronix MAXUM middle ear implant for severe high-frequency sensorineural hearing loss: preliminary results. Laryngoscope 2016;126: Hough JV, Matthews P, Wood MW, Dyer RK Jr. Middle ear electromagnetic semi-implantable hearing device: results of the phase II SOUNDTEC direct system clinical trial. Otol Neurotol 2002;23: Silverstein H, Atkins J, Thompson JH Jr, Gilman N. Experience with the SOUNDTEC implantable hearing aid. Otol Neurotol 2005;26: Roland PS, Shoup AG, Shea MC, Richey HS, Jones DB. Verification of improved patient outcomes with a partially implantable hearing aid, the SOUNDTEC direct hearing system. Laryngoscope 2001;111: Kahue CN, Carlson ML, Daugherty JA, Haynes DS, Glasscock ME III. Middle ear implants for rehabilitation of sensorineural hearing loss: a systematic review of FDA approved devices. Otol Neurotol 2014;35: Kraus E, Shohet J, Catalano P. Envoy Esteem Totally Implantable Hearing System: phase 2 trial, 1-year hearing results. Otolaryngol Head Neck Surg 2011;145: Shohet JA, Kraus EM, Catalano PJ. Profound high-frequency sensorineural hearing loss treatment with a totally implantable hearing system. Otol Neurotol 2011;32: Butler CL, Thavaneswaran P, Lee IH. Efficacy of the active middle-ear implant in patients with sensorineural hearing loss. J Laryngol Otol 2013;127(suppl 2):S8 S Luetje CM, Brackman D, Balkany TJ, et al. Phase III clinical trial results with the Vibrant Soundbridge implantable middle ear hearing device: a prospective controlled multicenter study. Otolaryngol Head Neck Surg 2002;126: Thornton A, Raffin M. Speech-discrimination scores modeled as a binomial variable. J Speech Hear Res 1978;21: Carney E, Schlauch RS. Critical difference table for word recognition testing derived using computer simulation. J Speech Lang Hear Lang Res 2007;50: Guthrie LA, Mackersie CL. A comparison of presentation levels to maximize word recognition scores. J Am Acad Audiol 2009;20: Boothroyd A. Developments in speech audiometry. Br J Audiol 1968;2: Ullrich K, Grimm D. Most comfortable listening level presentation versus maximum discrimination for word discrimination material. Audiology 1976;15: Beattie RC, Warren VG. Relationships among speech threshold, loudness discomfort, comfortable loudness, and PB max in the elderly hearing impaired. Am J Otol 1982;3: Beattie RC, Raffin MJ. Reliability of threshold, slope, and PB max for monosyllabic words. J Speech Hear Disord 1985;50: Beattie RC, Zipp JA. Range of intensities yielding PB max and the threshold for monosyllabic words for hearing-impaired subjects. J Speech Hear Disord 1990;55: Boothroyd A. The perception/intensity function: an underused resource. Ear Hear 2008;29: