Surgery Section - Cochlear Implant

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Description

A cochlear implant provides direct electrical stimulation to the auditory nerve, bypassing the usual transducer cells that are absent or nonfunctional in deaf cochlea. The basic components of a cochlear implant include both external and internal components. The external components include a microphone, an external sound processor, and an external transmitter. The internal components are implanted surgically and include an internal receiver implanted within the temporal bone, and an electrode array that extends from the receiver into the cochlea through a surgically created opening in the round window of the middle ear.

Sounds that are picked up by the microphone are carried to the external signal processor, which transforms sound into coded signals that are then transmitted transcutaneously to the implanted internal receiver. The receiver converts the incoming signals to electrical impulses that are then conveyed to the electrode array, ultimately resulting in stimulation of the auditory nerve.

Hearing loss is rated on a scale based on the threshold of hearing. Severe hearing loss is defined as a bilateral hearing threshold of 70-90 decibels (dB) and profound hearing loss is defined as a hearing threshold of 90 dB and above.

In adults, limited benefit from hearing aids is defined as scores 50% correct or less in the ear to be implanted on tape recorded sets of open-set sentence recognition. In children limited benefit is defined as failure to develop basic auditory skills, and in older children, equal to or less than 30% correct on open-set tests.

A post-cochlear implant rehabilitation program is necessary to achieve benefit from the cochlear implant. The rehabilitation program includes development of skills in understanding running speech, recognition of consonants and vowels, and tests of speech perception ability.

Next generation devices have typically offered a marginal improvement over previous devices, such that replacement of the internally implanted components is not routinely performed and thus may be considered medically necessary only in the small subset of patients who have an inadequate response to existing components. Upgrades of an existing, functioning external system to achieve aesthetic improvement, such as smaller profile components, or a switch from a body-worn, external sound processor to a behind-the-ear (BTE) model are considered not medically necessary.

Several cochlear implants are commercially available in the United States, the Nucleus® family of devices, manufactured by Cochlear™ Corporation, the Clarion® family of devices, manufactured by Advanced Bionics®; and the Med El Combi 40+ device, manufactured by Med El Corporation. Over the years, subsequent generations of the various components of the devices have been FDA approved, focusing on improved electrode design and speech-processing capabilities. Furthermore, smaller devices and the accumulating experience in children have resulted in broadening of the selection criteria to include children as young as 12 months. The FDA-labeled indications for currently marketed electrode arrays are summarized below.

While cochlear implants have typically been used mono laterally, in recent years, interest in bilateral cochlear implantation has arisen.  The proposed benefits of bilateral cochlear implants are to improve understanding of speech in noise and localization of sounds.  Improvements in speech intelligibility may occur with bilateral cochlear implants through binaural summation; i.e., signal processing of sound input from two sides may provide a better representation of sound and allow one to separate out noise from speech.  Speech intelligibility and localization of sound or spatial hearing may also be improved with head shadow and squelch effects, i.e., the ear that is closest to the noise will be received at a different frequency and with different intensity, allowing one to sort out noise and identify the direction of sound.  Bilateral cochlear implantation may be performed independently with separate implants and speech processors in each ear or with a single processor.  However, no single processor for bilateral cochlear implantation has been FDA approved for use in the United States.  In addition, single processors do not provide binaural benefit and may impair localization and increase the signal to noise ratio received by the cochlear implant.

Policy/Criteria

Scientific Background

Cochlear implants are recognized effective treatment of sensorineural deafness, as noted in a 1995 National Institutes of Health Consensus Development conference, which offered the following conclusions (2):

• Cochlear implantation has a profound impact on hearing and speech reception in postlingually deafened adults with positive impacts on psychological and social functioning.
• The results are more variable in children. Benefits are not realized immediately but rather are manifested over time, with some children continuing to show improvement over several years.
• Prelingually deafened adults may also benefit, although to a lessor extent than postlingually deafened adults. These individuals achieve minimal improvement in speech recognition skills. However, other basic benefits, such as improved sound awareness, may meet safety needs.
• Training and educational intervention are fundamental for optimal postimplant benefit.
• Cochlear implants in children under two years old are complicated by the inability to perform detailed assessment of hearing and functional communication. However, a younger age of implantation may limit the negative consequences of auditory deprivation and may allow more efficient acquisition of speech and language. Some children with postmeningitis hearing loss have been implanted under the age of 2 years due to the risk of new bone formation associated with meningitis, which may preclude a cochlear implant at a later date.

While use of a monolateral cochlear implant in patients with severe to profound hearing loss has become standard clinical practice, bilateral cochlear implants has been less common.  A literature review through December 18, 2007 identified a number of studies that are relevant to the use of bilateral cochlear implants.  Sharma and colleagues report that central auditory pathways are maximally plastic for a period of about 3.5 years. (3) Stimulation delivered within this period results in auditory evoked potentials that reach normal values in three to six months.  However, when stimulation occurs after seven years, changes occur within one month, but then have little to no subsequent change.  Sharma and Dorman also reported on auditory development in 23 children with unilateral or bilateral implants. (4) In one child who received a bilateral device with later (after age seven) implantation of the second ear the auditory responses in the second device were similar to that seen in “late-implanted” children.  A review of the peer-reviewed literature on MEDLINE from the period of 1995 through April 2006 identified 13 case reports on patients with bilateral cochlear implants. (3-15) The case reports identified range in size from 1 to 10 patients and most, but not all, patients reported slight to modest improvements in sound localization and speech intelligibility with bilateral cochlear implants especially with noisy backgrounds but not necessarily in quiet environments. When reported, the combined use of binaural stimulation improved hearing in the range of 1–4 decibels or 1%–2%. While this improvement seems slight, any improvement in hearing can be considered beneficial in the deaf.  However, this improvement appears marginal at best, and may not outweigh the significant risks of a second implantation.  In addition, similar binaural results can be achieved with a contralateral hearing aid, assuming the contralateral ear has speech recognition ability. (16)

A number of studies have reported benefits for patients with a unilateral cochlear implant with hearing aid (HA) in the opposite ear.  Ching reported on twenty-one adults who used unilateral cochlear implants and hearing aid in the opposite ear. (5) Binaural benefits were seen for at least one measure for their patients; measures included speech recognition, sound localization, and functional performance.  Ching and colleagues subsequently reported on 29 children and 21 adults with unilateral cochlear implant and a contralateral hearing aid. (6) They noted that both children and adults localized sound better with bilateral inputs.  In another report, Holt concluded that children who used cochlear implant and hearing aid benefited from combining the acoustic input, particularly in background noise. (7)

A number of studies have also reported results with bilateral cochlear implants.  Litovsky reported that nine of 13 (70%) children with bilateral cochlear implants discriminated source separations of equal to or less than 20 degrees and seven out of nine performed better when using bilateral (versus unilateral) devices. (8) Schoen and colleagues reported that bilateral cochlear implants were able to restore spatial hearing in eleven cochlear implant patients. (9) Litovsky and colleagues reported on a multi-center prospective study of 37 adults with post-lingual bilateral hearing loss. (10) Bilateral benefit (speech understanding in quiet and noise) was seen in 32/34 subjects.  Questionnaire data (subjects used only the best unilateral device for three weeks) also indicated that bilateral users perceived their performance to be better than when using a single device.  Ricketts and colleagues reported on 16 similar adults with post-lingual bilateral hearing loss. (11) They found a small but significant advantage for bilateral implants for speech recognition in noise.  While a training effect was noted over time for a subset of patients followed up to 17 months, a consistent bilateral advantage was noted.  Ramenden and colleagues reported on 30 adults in England who had bilateral cochlear implants and received their second implant a mean of three years after the first. (12) At nine months a significant (12.6%, p=less than 0.001) binaural advantage was seen for speech and noise from the front.  They were not able to predict when the second ear would be the better performer.  Sequential implantation with long delays between ears resulted in poor second ear performance for some of their subjects.  Kuhn-Uinacker reported on a group of 39 European children who had bilateral cochlear implants. (13) From qualitative and quantitative data, they concluded that bilateral implants improve the children’s communicative behavior, especially in complex listening situations.

The potential to restore cochlear function is not foreseeable in the near future (there is current research to restore hearing by stimulating cochlear hair cell regrowth); but destruction of the cochlea eliminates this possibility.  However, if implantation of cochlear implants is felt to be most beneficial at a younger age when the nervous system is “plastic”, this potential development seems too far in the future to benefit young children who are current candidates for a cochlear implant.

In summary, these studies show consistent improvement in speech reception (especially in noise) and in sound localization with bilateral devices.  These are important attributes.  Studies also suggest that earlier implantation may be preferred.  Based on these new studies, bilateral cochlear implants have been shown to improve clinical outcomes.

An updated search of the MEDLINE database through December 18, 2007 failed to return any new clinical trials that alter the conclusions reached above.

References

1. BlueCross and BlueShield Association Medical Policy Reference Manual, Policy No. 7.01.05
2. 1995 NIH Consensus Conference: Cochlear Implants in Adults and Children.  NIH Consensus Statement Online 1995 May 15-17;13(2):1-30.  (Verified 12/18/07)
3. Sharma A, Dorman MF. Central auditory development in children with cochlear implants: clinical implications. Adv Otorhinolaryngol. 2006;64:66-88
4. Sharma A, Dorman MF, Kral A. The influence of a sensitive period on central auditory development in children with unilateral and bilateral cochlear implants. Hear Res. 2005;203:134-43
5. Ching TY, Incerti P, Hill M. Binaural benefits for adults who use hearing aids and cochlear implants in opposite ears. Ear Hear 2004;25:9-21
6. Ching TY, Incerti P, Hill M et al. An overview of binaural advantages for children and adults who use binaural/bimodal hearing devices. Audio Neurotol 2006;11(suppl):6-11
7. Holt RF, Kirk KI, Eisenberg LS et al. Spoken word recognition development in children with residual hearing using cochlear implants and hearing aids in opposite ears. Ear Hear 2005;2682S-91S
8. Litovsky RY, Johnstone PM, Godar S et al. Bilateral cochlear implants in children: localization acuity measures with minimum audible angle. Ear Hear. 2006;27:43-59
9. Schoen F, Mueller J, Helms J et al. Sound localization and sensitivity to interaural cues in bilateral users of the Med-El Combi 40/40+cochlear implant system. Otol Neurotol. 2005;26:429-37
10. Litovsky R, Parkinson A, Arcaroli J et al. Simultaneous bilateral cochlear implantation in adults: a multicenter clinical study. Ear Hear. 2006;27:714-31
11. Ricketts TA, Grantham DW, Ashmead DH et al. Speech recognition for unilateral and bilateral cochlear implant modes in the presence of uncorrelated noise sources. Ear Hear. 2006;27:763-73
12. Ramsden R, Greenham P, O’Driscoll J et al. Evaluation of bilaterally implanted adult subjects with the nucleus 24 cochlear implant system. Otol Neurotol. 2005;26:988-98
13. Kuhn-Uinacker H, Shehata-Dieler W, Juller J et al. Bilateral cochlear implants: a way to optimize auditory perception abilities in deaf children. Int J Pediatr Otorhinolaryngol 2004;68:1257-66

Cross References

Implantable Bone Conduction Hearing Aid, Regence Medical Policy Manual, Surgery, Policy No. 121

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