Assessment of bilateral cochlear implants in children and adults in Spain

In mid-November, 2018, the Catalan Agency for Quality and Healthcare Evaluation, AQuAS, published their evaluation of bilateral cochlear implants in children and adults. The authors provided a list of criteria a patient has to fulfil in order to have a cochlear implant prescribed.

The cochlear implant (IC) is an electronic device that allows the stimulation of auditory nerve fibres after surgical implantation. Therefore, an essential requirement to insert an IC is that individuals have intact, from a functional point of view, the cochlear nerve and the auditory pathways.

AQuAS has been asked by the General Subdirectorate of the Basic Portfolio of Services and the Cohesion Fund of the Spanish Ministry of Health, Social Services and Equality to perform a brief assessment to see if there is sufficient evidence of their utility and cost-effectiveness. The objective of this assessment was to establish criteria for the appropriate use of these devices, making a path for the creation of a protocol applicable in the Spanish national health system.

The authors have performed a systematic search of the literature published after May 2014 on different websites, such as PubMed, The Cochrane Library, Web of Science, Centre for Reviews and Dissemination, TRIPDatabase, NICE Evidence and Google. Only systematic reviews (and meta-analyses) were taken into account with target population being children and adults with bilateral sensorineural loss of hearing severe to profound, either pre-locutive or pre-lingual, or post-locutive or post-lingual. These systematic reviews should be comparing simultaneous or sequential (or deferred) bilateral cochlear implants and unilateral cochlear implants (or bimodal stimulation (ICU plus contralateral hearing aid). Systematic reviews of high quality (1++, according to the Scottish Intercollegiate Guidelines Network (SIGN)), written in English or Spanish, were included. Eventually, 10 systematic reviews of high quality were considered for the publication.

Authors’ conclusions

• The authors agree on some benefits of the bilateral over unilateral cochlear implants, for example, better speech perception in noisy environments and better identification of the sound source (observed in children and post-lingual adults; other outcomes were assessed, too)
• The data is insufficient to draw conclusions for pre-lingual adults
• Adverse events seem to be rare. However, the authors call for caution and note that current safety measures must be maintained to ensure that this situation does not change
• The additional cost per one QALY (or incremental cost-utility ratio) for second cochlear implant varies among studies ($30,973 - $94,340) in the pediatric population
• The additional cost per one QALY (or incremental cost-utility ratio) for second cochlear implant varies even more among the studies ($38,189 - $132,160) in the adult population
• However, although the gain exists, most of the studies do not consider it as a significant fact, because the first cochlear implant provides the biggest improvement
• Summed up, although the bilateral cochlear implants provide additional benefits and have a favourable cost-utility ratio unless they meet the 5 criteria mentioned below, unilateral cochlear implants are the best option

Criteria for indication of cochlear implants to children (grade recommendation from [A] to [D], [A] being the highest quality recommendation; good clinical practice [X])

Clinical experts recommend compliance with the following five criteria before performing a cochlear implant in children. [X]

Criterion 1: Severe bilateral sensorineural hearing loss (hearing loss 71-90 dB) to profound (hearing loss> 90 dB) or total (hearing loss> 119 dB) in children 5 years old up to 17 years old [grade C]

• In children under 5 years of age, the audiometric criterion is more restrictive, that is, the cochlear implant is indicated for profound bilateral hearing loss (> 90 dB) [X]
• The ideal age to recommend the cochlear implant is before 2 years of age. After age 8-10, the performance of the cochlear implant will be lower, and an individual assessment is necessary and always a period of tests with a hearing aid for 3-6 months [X]
• As parents of children with hearing loss are responsible for deciding whether or not to insert the cochlear implant, it is essential to ensure informed medical consent [X]

Criterion 2: Pre-locutive, peri-locutive and post-lingual hearing loss [C]

Criterion 3: No benefit or minimal benefit with hearing aid according to (silent) language recognition test score after a 3-6 month trial period [D]

• It is considered that the benefit is insufficient if the tonal thresholds at conversational frequencies are higher than 50 dB, or the recognition of disyllables is less than 40% (in lists of standardized and balanced words in open context and at 65 dB in silence) [X]
• Before 5 years of age, it is not possible to perform oral audiometry tests in the absence of language development. Therefore, tonal threshold determinations must be made, either with behavioural or objective audiometry by auditory evoked potentials [X]
• In children, during the testing period, speech, language and comprehension skills should be assessed, taking into account the age, developmental status and cognitive ability of each child [D]
• In very young children, the testing time has to be extended to ensure that the maximum possible benefit has been obtained [D]
• The tests must take into account the person's disabilities, whether physical or cognitive, linguistic or other and adapt them when necessary. If it is not possible to administer a test due to a lack of skills to do it properly, other tests will be considered [D]

Criterion 4: A prior psychological and neurological evaluation is required to confirm the benefit that the cochlear implant will bring [D]

• A psychological evaluation prior to the cochlear implant is recommended as a point of reference to evaluate the impact of the cochlear implant in the adaptation of the child to his new situation [D]

Criterion 5: Perform diagnostic imaging (computed tomography [CT], magnetic resonance imaging [MRI], or both) that demonstrate the existence of a cochlea sufficiently developed to house the electrode and confirm the presence of the cochlear nerve [X]

When these five criteria are met, there is the possibility of insertion of a unilateral cochlear implant or a bilateral cochlear implant. In the latter case, the insertion can be done in the same surgical act (simultaneous bilateral cochlear implant) or in two more or less consecutive surgeries (delayed or sequential bilateral cochlear implant).

When the cause of hearing loss is infectious or is associated with other disabilities (post-meningitis, post-cytomegalovirus or post-infectious hearing loss, hearing loss associated with blindness, presence of other multisensory deficits, USHER syndrome (associated with progressive loss of vision)), the option of simultaneous bilateral cochlear implant should be the intervention to recommend. [X]

When the child already has a (unilateral) cochlear implant, and other pathologies are present, or the evolution is not as expected (when a new pathology that may interfere with the results of the first implant, malformations of the inner ear with little unilateral functional result, attention deficit hyperactivity disorder (ADHD) or other behavioral disorders associated with hearing loss, Pendred syndrome or other hereditary diseases associated with progressive bilateral loss), the option of the sequential bilateral cochlear implant is the recommended surgical alternative. [X]

When none of the above circumstances affect the child, the recommendation is to implement a unilateral cochlear implant given the situation of limited resources for this intervention in the public health system. [X]

Criteria for indication of cochlear implants to adults (grade recommendation from [A] to [D], [A] being the highest quality recommendation; good clinical practice [X])

Clinical experts recommend compliance with the following five criteria before performing a cochlear implant in adults. [X]

Criterion 1: Severe to profound or total bilateral sensorineural hearing loss (hearing loss 71-90 to> 91dB) at conversational frequencies (500 to 4,000 Hz) in adults of any age, but with a life expectancy of more than 3-5 years [C]

• In the mild or moderate hearing loss at all frequencies, the cochlear implant is not indicated, as the patients usually benefit from the hearing aids [X]

Criterion 2: Post-lingual hearing loss [C]

• In adults with post-lingual hearing loss, an individualized assessment is recommended if the deprivation of hearing happened more than 35-40 years ago [X]
• There is not enough evidence to recommend cochlear implant in adults with bilateral prelingual hypoacusis in a generalized way [C]. However, an individualized assessment of the actual degree of hearing, the educational setting (oralist vs. sign language) and patient expectations is recommended [X]

Criterion 3: No benefit or minimal benefit obtained with the best hearing aids at both the tonal and functional levels after a trial period of 3-6 months [D]

• It is considered that the benefit is insufficient if the tonal thresholds at conversational frequencies are higher than 50 dB, or the recognition of disyllables is less than 40% (in lists of standardized and balanced words in open context and at 65 dB in silence) [X]
• The tests must take into account the person's disabilities, whether physical or cognitive, linguistic or other and adapt them when necessary. If it is not possible to administer a test for lack of the skills to do it properly, other evaluation tests have to be considered [X]

Criterion 4: Convincing the patient that the hearing improvement that the cochlear implant will bring will benefit him personally and socially. Previous personal, work and psychological evaluations are recommended [X]

• It is recommended to consider the cochlear implant when the hearing loss causes important adverse effects in the HRQoL of the person in order to reduce its impact [X]

Criterion 5: Perform diagnostic imaging (CT, MRI, or both) that demonstrates the existence of a cochlea sufficiently developed to store the electrode and confirm the presence of the cochlear nerve [X]

• When these five criteria of indication are met, the most accepted and recommended option, in general, in adult patients is the unilateral cochlear implant [X]
• It is recommended that simultaneous bilateral cochlear implant be the first treatment option when the patient is blind or has other disabilities that increase their confidence with the auditory stimulus as a primary sensory mechanism in their spatial orientation; also in working-active adults, acute hearing loss or post-meningitis patients [X]
• When the patient already has a cochlear implant, the deferred option will be the viable option, but it is recommended that the benefit shown by the second implant in psychological, family and social aspects has been demonstrated before [D]
• In adults, age at implantation is an independent prognostic factor of the auditory deprivation factor (more satisfactory results at younger ages). Also, the shorter the period between implants, the better prognosis the intervention will have. In any case, there are benefit results after 9-10 years of auditory deprivation, although it is necessary to take into account the cerebral plasticity that can vary between individuals [X]
• The bilateral cochlear implant is a not recommended option when the time of auditory deprivation of one ear is great with respect to the other in cases of symmetric hearing loss. In these cases, it is recommended to implant only in the ear with a shorter period of auditory deprivation, agreeing on the decision with the patient and taking into account their laterality (right- or left-handed) [X]

There are two indications for cochlear implants that are currently under study:

• Asymmetric hearing loss (deep in one ear and moderate in the other). In these cases, a unilateral cochlear implant is recommended in the ear with profound hearing loss, as long as the cause of moderate hearing loss in the other ear is progressive (e.g. autoimmune disease and Ménière's syndrome) [D]
• Deep hearing loss in acute sounds (> 1,000 Hz) with preservation of low-frequency sounds. In these cases, electroacoustic stimulation with hybrid implants (devices configured by a cochlear implant and a hearing aid) is recommended [D]

See the full report in Spanish (with summary in English) here.

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