A semi-implantable middle ear hearing aid device is an alternative to an externally worn acoustic hearing aid which uses air pressure to transport sound to the middle ear. This document addresses the use of a semi-implantable middle ear hearing aid, which uses the periodic attraction and repulsion of two magnetic fields, one from an electromagnet and the other from a static magnet, as a means of vibrating ossicles and transmitting sound to the inner ear. 

Note: Please see the following documents related to the treatment of hearing loss:

• SURG.00014 Cochlear Implants and Auditory Brainstem Implants
• SURG.00020 Bone-Anchored Hearing Aids

Investigational and Not Medically Necessary:

Semi-implantable middle ear hearing aids are considered investigational and not medically necessary for all indications.

Externally worn acoustic hearing aids are widely accepted devices for patients with moderate to severe sensorineural hearing loss. There is inadequate clinical evidence in the peer reviewed medical literature that focuses on various audiologic measures achieved with an externally worn acoustic hearing aid compared to a semi-implantable hearing aid in the same patient. In the available studies, patients served as their own controls, and the efficacy of the semi-implantable hearing aid was determined by comparing the results of pre- and postimplant audiometric tests and audiologic questionnaires. Additional outcome measures include patient satisfaction with fit and comfort and with the quality and clarity of sound. Patient preference for an implantable device compared to an externally worn device was considered, however, it must be determined to what extent patient preference is based on convenience compared to preference based on improved hearing.

There are minimal safety concerns related to externally worn hearing aids. In contrast, a semi-implantable hearing aid requires a surgical procedure for implantation. Potential risks cited for a semi-implantable hearing aid include a decrease in residual hearing in the implanted ear and infection in the ear and adjacent structures. Major ear surgery may also result in numbness, swelling, or discomfort around the ear, the possibility of facial paresis, neck pain, and disturbance of balance and taste. Therefore, equivalency or improvement in audiologic outcomes associated with a semi-implantable hearing aid must be balanced against the potential risks inherent in a surgical procedure.

In a small study of 20 patients, Schmuziger and colleagues (2006) assessed long-term results with a semi-implantable middle ear implant and analyzed pre- and post-operative results of audiologic tests. The study involved retrospective chart review with additional patient interview and audiologic testing. Assessments were made of clinical outcome benefit and satisfaction using the standardized International Outcome Inventory for Hearing Aids, the Glasgow Benefit Inventory, and Visual Analogue Scales in all patients. Fifteen patients agreed to undergo audiologic testing at follow-up, including pure-tone and speech audiometry in silence and noise. The authors concluded that satisfaction with the semi-implantable middle ear device was not superior to conventional hearing aids in subjective and in audiometric terms.

The U.S. Food and Drug Administration (FDA) approval of the Vibrant^® P/D Soundbridge™ Systems (Symphonix Devices, Inc., San Jose, CA) (FDA, 2000) and SOUNDTEC^® Direct Drive Hearing System (DDHS) (SOUNDTEC, Inc., Oklahoma City, OK) (FDA, 2001) was based in part on clinical trials of 53 and 103 patients respectively, who had bilateral moderate to severe sensorineural hearing loss and who were dissatisfied with their existing external acoustic hearing aid. Results of these trials are available in the FDA Summaries of Safety and Effectiveness (Vibrant Soundbridge, 2000; SOUNDTEC Direct, 2001). 

The results of the Soundbridge and SOUNDTEC trials have also been reported in the peer-reviewed published literature (Luetje, 2002; Hough, 2002). The principal audiologic outcome measures, before (with the hearing aid in use) and after the implant, are summarized below.

Functional Gain

Functional gain is defined as the difference in sound field threshold (measured in decibels) and is an indicator of functional benefit from an amplification device. For the Soundbridge device, the improvement in functional gain was 14.1 (dB) decibels, while for the SOUNDTEC device it was 7.9 dB, both considered a modest improvement. The clinical significance of this improvement is difficult to determine. For example, this level of improvement may be more clinically significant in patients with moderate hearing loss, for whom a 14-dB improvement in threshold might move them into the normal range for the spoken voice.

Speech Recognition 

Speech recognition is assessed using the Speech Perception in Noise (SPIN) test, or the Northwestern University-6 test (NU-6), which consists of a 50-item word list. For the Soundbridge device, no significant difference in word recognition was found in quiet or noisy conditions between the implant and acoustic hearing aid. For the SOUNDTEC device, a statistically significant improvement was noted in results of the NU-6 and SPIN test at 52 weeks compared to an optimally fitted hearing aid. The results, however, are limited by the small study population and a high dropout rate at 36 weeks (n=33) and at 52 weeks (n=12) (Hough, 2002) which limits the statistical significance of drawing any long term conclusions related to these outcome measurements.

Patient Assessments

Patient self-evaluation was performed with a number of methods. The Profile of Hearing Aid Performance (PHAP) consists of seven subscales that measure several dimensions of hearing aid effectiveness, such as ease of communications, reverberation, distortion of sound, etc. The Hearing Device Satisfaction Scale (HDSS) was developed by Symphonix, the manufacturer. This scale evaluated the general satisfaction level with an acoustic hearing aid compared to the Soundbridge device. The number of subjects who reported improvement with hearing effectiveness was significant across all seven subscales of the PHAP. The most significant improvements in the Soundbridge compared to the acoustic hearing aid were reported for reverberation, reduced cues, and background noise. Based on the HDSS, 94% reported improved overall sound quality for the Soundbridge. For the SOUNDTEC device, patient satisfaction was based on the Hough Ear Institute Profile. This profile assesses patient preference, acoustic feedback, perception of speech quality, occlusion, and tinnitus. At 20 weeks post-implant, improvements in all of the parameters were clinically significant with 89% of patients preferring the implantable hearing aid to the acoustic hearing aid. A total of 67% of patients reported experiencing feedback with their previous acoustic hearing aid, while only 9% reported feedback with the implanted device. These results, however, are subject to bias since only patients who were dissatisfied with their previous acoustic hearing participated in the trial. 

Safety
 
Minimal safety issues appeared associated with either device. In the Soundbridge device, the most common complication was a fullness sensation reported by 18 patients, which remained unresolved in 13 patients. Altered taste sensation was reported in seven patients and transient pain in 13 patients. Two patients reported a reduction in residual hearing. The most common complications reported with the SOUNDTEC device include device noise, ear pain, ear irritation, and processor failure. These complications resolved in almost all patients; no patient requested removal of the device. However, risks can only be adequately evaluated in broader populations over time.

Summary

The limited data suggests that semi-implantable middle ear hearing aids may provide a marginal improvement in hearing compared to conventional external acoustic hearing aids. The clinical significance of the improvement in functional gain, speech perception, and hearing ability in various listening situations is uncertain, although there appears to be a clear patient preference for the implantable devices (Sterkers, 2003). However, given the safety and effectiveness of external acoustic hearing aids, and the increased risks inherent in a surgical procedure, an implantable device must be associated with clinically significant improvement in various hearing parameters compared to external hearing aids.  While safety concerns appear to be minimal, only a limited number of patients were included in the clinical trials, and few have completed more than one year of follow-up.

An additional retrospective case series was reported by Silverstein and colleagues (2005) assessing the efficacy, morbidity, and patient satisfaction with the SOUNDTEC device. The 64 patients fitted with the SOUNDTEC device (four with bilateral device placements) had bilateral, moderately severe sensorineural hearing loss. Forty-seven of these patients had previously worn a conventional hearing aid. The average functional gain varied with frequency, with the lowest functional gain in the lower speech frequencies (7.9 dB), with increasing functional gain at higher frequencies, ranging up to 27 dB at the highest frequency of 6, 000 Hz. The functional gain of 7.9 dB at the speech frequencies is similar to that reported in the FDA summary of safety and effectiveness, while it is markedly higher in the higher frequencies. The cause of this marked discrepancy is not apparent. The authors also reported that a high percentage (55%) of patients complained of magnet movement inside the ear. This was reported as being eliminated in 80% of the patients when the external processor was worn and the surgical procedure was refined by using adipose tissue to better stabilize the magnet. However, four patients required removal of the device and three patients underwent revision surgery for magnet stabilization. This study was limited to a 30-day post-operative follow-up evaluation. The authors conclude that "further testing will be needed to reassess this potentially promising device."

In summary, studies suggest that the semi-implantable middle ear hearing aid may provide functional hearing gains, improved satisfaction, and a decreased occurrence of feedback and occlusion in carefully selected patients. However, only a limited number of patients have been studied in clinical trials and long-term follow-up measures of durability, efficacy and safety have not been reported. Given the small number of patients studied and limited safety data, risks cannot be evaluated and compared with the marginal improvement in hearing demonstrated to date in early clinical trials.

The basic types of hearing loss are conductive, sensorineural and mixed hearing loss. Conductive hearing loss involves the outer and middle ear and is due to mechanical or physical blockage of sound. It can result from a blockage of wax, a punctured eardrum, birth defects, ear infections or heredity. Sensorineural or "nerve" hearing loss involves damage to the inner ear or the eighth cranial nerve. It can be caused by aging, prenatal or birth-related problems, viral or bacterial infections, heredity, trauma, exposure to loud noises, the use of certain drugs, fluid buildup in the middle ear, or a benign tumor in the inner ear (acoustic neuroma). Mixed hearing loss is conductive hearing loss coupled with sensorineural hearing loss.

Sensorineural hearing loss is most commonly managed with a hearing aid. Since this type of hearing loss can affect selective portions of a person's range of hearing, the degree of hearing loss and the specific pitches affected will vary from person to person. Even in instances where the pattern of the loss is the same, the degree of sound clarity may vary from person to person or may differ between ears in an individual. As a result, individuals suffering from sensorineural hearing loss often require hearing aids tailored to the specific sensitivity and pattern of their hearing loss. Normal speech and conversation occurs at 40-60 dB within a frequency range of 500-3000 Hertz. Degree of hearing loss (HL) refers to the severity of the loss. There are five broad categories that are typically used, with the numbers representative of the patient's thresholds, or the softest intensity that sound is perceived: mild loss (20 dB to 40 dB), moderate loss (40 dB to 60 dB), severe loss (60 dB to 80 dB), and profound loss (80 dB or more) (ASHA, 2007).  

The most common type of hearing aid for moderate to severe sensorineural hearing loss is an external acoustic hearing aid, which is placed into the external ear canal and functions to amplify sound. However, these hearing aids may not be acceptable to patients, either due to issues related to anatomic fit, sound quality, or personal preference. A semi-implantable middle ear hearing aid has been developed as an alternative to an external acoustic hearing aid. Two such devices have received approval by the FDA for use in adults, 18 years of age or older, who have moderate to severe sensorineural hearing loss and desire an alternative to an acoustic hearing aid.

The semi-implantable middle ear hearing aid device consists of three components: a magnetic component that is implanted onto the ossicles of the middle ear, a receiver, and a sound processor. The Soundbridge device is implanted subcutaneously behind the ear, while the SOUNDTEC device is placed in the ear canal. In the Soundbridge device, the processor is worn externally on the scalp over the receiver unit, held in place by a magnet, while in the SOUNDTEC device the processor rests over the external ear. In general the sound processor receives and amplifies the sound vibrations and transforms the sound pressure into electrical signals that are received by the receiver unit. The receiver unit then transduces these electrical signals into electromagnetic energy and creates an alternating electromagnetic field with the magnetic component implanted on the ossicles of the middle ear. This electromagnetic field results in attractive and repulsive forces on the magnetic implant, causing vibration of the bones of the middle ear similar to normal hearing.

There is a fundamental difference in principle as to how sound is amplified and delivered to the inner ear between the conventional (acoustic) hearing aid and an implantable middle ear hearing aid device. An acoustic hearing aid receives sound from a microphone, amplifies and processes it and in turn reproduces increased acoustic sound pressure energy in the ear canal. In contrast, the implantable aid receives sound from a microphone, amplifies and processes it according to frequency shaping, and then delivers directly an electrical signal to an electromagnetic coil in the ear canal. This coil produces an electromagnetic field within the middle ear space which stimulates a magnet surgically attached under local anesthesia to the ossicular chain (stapes). Vibrations produced in the stapes are then delivered via the ossicular chain to the cochlea.

Conductive hearing loss: occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the small bones (ossicles) of the middle ear; involves a reduction in sound level or the ability to hear faint sounds

Mixed hearing loss:  conductive hearing loss in combination with a sensorineural hearing loss; damage exists in the outer or middle ear and also in the inner ear (cochlea) or auditory nerve, in one or both ears

Sensorineural hearing loss: a type of permanent hearing loss related to the vestibulocochlear nerve (cranial nerve VIII), the inner ear, or central processing centers of the brain; hearing loss that involves a reduction in sound level or ability to hear faint sounds; affects speech understanding or the ability to hear clearly

The following codes for treatments and procedures applicable to this document are included below for informational purposes.  Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy.  Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member. 

When services are Investigational and Not Medically Necessary:

Peer Reviewed Publications:

1. Coletti V, Soli SD, Carner M, Colletti L. Treatment of mixed hearing losses via implantation of a vibratory transducer on the round window. Int J Audiol. 2006; 45(10):600-608.
2. Hough JV, Matthers P, Wood MW, Dyer RK. Middle ear electromagnetic semi-implantable hearing device: results of the phase II SOUNDTEC direct system clinical trial. Otol Neurotol. 2002; 23(6):895-903.
3. 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(2):97-107.
4. Roland PS, Shoup AG, Shea MC, et al. Verification of improved patient outcomes with a partially implantable hearing aid, the SOUNDTEC direct hearing system. Laryngoscope. 2001; 111(10):1682-1686.
5. Schmuziger N, Schimmann F, Wengen D, et al. Long-term assessment after implantation of the Vibrant Soundbridge device. Otol Neurotol. 2006; 27(2):183-188.
6. Silverstein H, Atkins J, Thompson JH, Gilman N. Experience with the SOUNDTEC implantable hearing aid. Otol Neurotol. 2005; 26(2):211-217.
7. Snik AF, Mylanus EA, Cremers CW, et al. Multicenter audiometric results with the Vibrant Soundbridge, a semi-implantable hearing device for sensorineural hearing impairment. Otolaryngol Clin North Am. 2001; 34(2):373-388.
8. Sterkers O, Boucarra D, Labassi S, et al. A middle ear implant, the Symphonix Vibrant Soundbridge: retrospective study of the first 125 patients implanted in France. Otol Neurotol. 2003; 24(3):27-36.
9. Uziel A, Mondain M, Hagen P, et al. Rehabilitation for high-frequency sensorineural hearing impairment in adults with the Symphonix Vibrant Soundbridge: a comparative study. Otology and Neurotology. 2003; 24(5):775-783.

Government Agency, Medical Society, and Other Authoritative Publications:

1. Hayes Inc. Hayes Medical Technology Directory. Semi-Implantable Electromagnetic Hearing Aids. Lansdale, PA: Hayes Inc.; May 2002. Search updated May 13, 2009.
2. U.S. Food and Drug Administration (FDA) Premarket Notification Database. SOUNDTEC^® Direct System^SM Summary of Safety and Effectiveness. No. P010023. Rockville, MD: FDA. September 7, 2001. Available at:http://www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm. Accessed on June 23, 2009.
3. U.S. Food and Drug Administration (FDA) Premarket Notification Database. Vibrant P/Vibrant D Soundbridge System. FDA Summary of Safety and Effectiveness.  No. P990052a and No. P990052b. Rockville, MD: FDA. August 2000. Available at: http://www.accessdata.fda.gov/scripts/cdrh/devicesatfda/index.cfm. Accessed on June 23, 2009.

1. American Speech-Language-Hearing Association (ASHA). Public information. Hearing loss. Types of hearing loss. Available at:   http://www.asha.org/public/hearing/disorders/types.htm. Accessed on June 23, 2009.
2. National Institute on Deafness and Communication Disorders (NIDCD). Hearing aids. Available at: http://www.nidcd.nih.gov/health/hearing/hearingaid.asp. Accessed on June 23, 2009.  

Semi-Implantable Middle Ear Hearing Aids
SOUNDTEC^® Direct System^SM
Vibrant^® D Soundbridge^® System
Vibrant^® P Soundbridge^® System

The use of specific product names is illustrative only. It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.