A cochlear implant is a biomedically engineered device that can help restore hearing and speech communication skills to deaf individuals. Since cochlear implantation is a new technology in the field of medicine and rehabilitation, there is a need for a reference standard for the selection of indications, pre- and post-operative evaluation, surgery, post-operative tuning and auditory speech rehabilitation. The purpose of this guideline is to provide guidance to clinicians, audiologists and speech and language rehabilitators who are involved in this work, so that cochlear implantation in China can be standardized and standardized, thereby improving outcomes and avoiding unnecessary risks.
Cochlear implantation involves many fields of medicine, audiology, biomedical engineering, education, psychology and sociology, and requires the collaboration of otologists, audiologists, speech therapists, rehabilitation teachers, engineers and parents to form a cochlear implant team.
Selection of Indications
I. Patient selection criteria
For patients with severe or profound deafness in both ears and lesions localized and diagnosed in the cochlea, cochlear implantation can be selected.
1. Selection criteria for patients with prelingual deafness.
① Severe or profound sensorineural deafness in both ears.
②The best age should be 12 months to 5 years.
③With appropriate hearing aids, no significant improvement in auditory language ability after 3-6 months of aural rehabilitation training.
④No contraindication to surgery.
⑤ The family and/or the implant recipient has a correct understanding of the cochlear implant and appropriate expectations.
⑥The condition of hearing and language rehabilitation education is available.
The younger the patient is at the time of surgical implantation, the better the outcome, as this maximizes the potential to avoid auditory sensory deprivation and expand speech and language skills before the critical period of brain plasticity. Children or adolescents older than 6 years of age need to have some auditory-verbal foundation, a history of hearing aid wear and a history of hearing or speech training since childhood. Ineffective or very poor hearing aids are defined as open phrase recognition ≤ 30% or two-word word recognition ≤ 70% in the best hearing aid listening environment.
2. Selection criteria for patients with postlingual deafness.
①Patients of all ages with postlingual deafness.
②Severe or very severe sensorineural deafness in both ears.
③ Hearing aid is ineffective or very poor, open phrase recognition rate ≤ 30%;
④No contraindication to surgery.
⑤ have good psychological quality and initiative, correct understanding of cochlear implants and appropriate expectations
⑥ Have the support of family.
The age of onset and duration of deafness of post-speech deafness patients are closely related to the outcome after surgery. Generally speaking, those with early age of onset and longer duration of deafness have poorer post-surgical results. In addition, the listening environment in life and work after surgery can also affect the outcome of cochlear implantation.
3. Contraindications to surgery.
(1) Absolute contraindications, including severe malformations of the inner ear, such as Micheal malformation and cochlear malformation; auditory nerve deficiency; severe intellectual disability; inability to cooperate with language training; severe mental illness; acute and chronic inflammation of the middle ear mastoid that has not been cleared.
② Relative contraindications, including poor general condition of the body; uncontrollable epilepsy; no reliable conditions for rehabilitation training.
Secretory otitis media and glue ear are not contraindications to surgery. In chronic otitis media with tympanic membrane perforation, if the inflammation is under control, one-stage or staged surgery is an option. One-stage surgery means the eradication of the middle ear mastoid lesion, tympanic membrane repair (or mastoid cavity temporal muscle filling and closure of the external ear canal) along with cochlear implantation. Staged surgery means removing the lesion first, repairing the tympanic membrane perforation or closing the external ear canal, and performing cochlear implantation 3-6 months later.
Pre-operative evaluation
1. Medical history taking: Medical history taking and examination should be used to understand the cause of the disease. The otologic history should focus on the etiology and pathogenesis of deafness. The patient’s hearing history, history of tinnitus and vertigo, history of ototoxic drug exposure, history of noise exposure, history of systemic acute and chronic infections, past otologic history, developmental factors (systemic or local developmental abnormalities, intellectual development, etc.), family history of deafness, history of hearing aid wear, and other causes such as epilepsy and psychiatric conditions should be understood. Children with deafness should also include: maternal pregnancy history, pediatric birth history, pediatric growth history, and speech development history. The patient’s language ability (e.g., articulation characteristics, intelligibility of constructions) and language comprehension and communication ability (e.g., oral, lip reading, sign language, written, guessing, etc.) should also be understood.
2.Otological examination includes the auricle, external auditory canal, tympanic membrane and eustachian tube, etc.
3.Hearing mechanics examination.
①Subjective hearing threshold determination: pediatric behavioral audiometry can be used for children under 6 years old, including behavioral observation audiometry, visual reinforcement audiometry and play audiometry.
②Acoustic conductance measurement: including tympanic chamber pressure curve and stapedius muscle reflex.
③Auditory brainstem response (ABR), 40 Hz correlation potential (or multi-frequency steady-state evoked potentials);
(iv) Otoacoustic emissions (transient evoked otoacoustic emissions or aberration product otoacoustic emissions);
⑤ Speech audiometry: speech hearing threshold test for speech perception threshold and speech recognition threshold; speech recognition test including speech test word list and pediatric speech test word list.
(6) Hearing aid matching: professional audiologists are required to match hearing aids, which are usually worn in both ears, and the hearing aid threshold test and speech recognition test should be done after matching, and then auditory language training should be conducted for 3-6 months.
(7) Vestibular function test (for those with a history of vertigo);
⑧ Drum head electrical stimulation test: the test includes threshold, dynamic range, frequency discrimination, interval discrimination and temporal discrimination and other psychophysical examinations.
Audiological evaluation criteria.
①Patients with postlingual deafness: Binaural pure tone air conduction hearing threshold measurement > 80 dBHL (average of 0, 5, 1, 2, 4 kHz, WHO criteria). Cochlear implants may also be considered if the good ear does not achieve 30% open phrase recognition and the hearing loss is greater than or equal to 75 dB [see FDA supplemental criteria];
②Patients with prelingual deafness: For infants and young children, a comprehensive assessment after multiple objective audiometry and behavioral audiometry is required, including: no auditory response during ABR examination of acoustic output (120 dBSPL); no response during 40 Hz correlation potential detection of loudest output at frequencies above 2 kHz and frequencies below 1 kHz > 100 dB; no response during multi-frequency steady-state audiometry at frequencies above 2 kHz 105 dBHL response; no response at all frequencies in both ears for aberration product otoacoustic emission; hearing threshold does not enter the auditory language area (banana chart) at frequencies above 2kHz for helpful sound field audiometry, and the speech recognition rate (two-word words) score is below 70%, confirming that the child cannot receive effective help from hearing aids.
③ For patients without any residual hearing, cochlear implantation may still be considered if there is a clear auditory response to electrical stimulation of the tympanic capsule. If there is no auditory response to electrical stimulation of the tympanic capsule, the patient or parents should be informed of the situation and they should assume the surgical risk.
4. Imaging evaluation: Imaging is a crucial test for patient selection. A thin layer CT scan of the temporal bone should be routinely done, and if necessary, cranial magnetic resonance, three-dimensional reconstruction of the cochlea and a cross-sectional scan of the inner ear canal are required.
5. Language ability assessment: For patients with certain language experience or ability, speech ability assessment (language structure and function) should be done, including speech intelligibility, vocabulary, comprehension, grammatical ability, expression and communication ability; for uncooperative children less than 3 years old, the “parent-child game” video observation method should be used for evaluation. For children younger than 3 years old who were uncooperative, a “parent-child play” video was used to evaluate the patient’s language ability at this stage.
6. Psychological, intellectual and learning ability assessment: For children over 3 years of age who lack language ability, the Schneider Learning Ability Test can be used; for those under 3 years of age, the Greifers Mental Developmental Behavior Assessment Scale can be used. For those suspected of having mental retardation (IQ < 68 on the Hine Learning Ability Assessment and mental developmental quotient < 70 on the Greifers Test) or abnormal psychological behavior, patients should be advised to go to an authoritative institution for further observation, diagnosis and identification. Patients with socio-cultural mental retardation may be considered for cochlear implantation; while patients with non-socio-cultural mental retardation, or ADHD, autism and other mental retardation should be advised to explain to their parents the great difficulties that such disorders may bring to their post-operative rehabilitation, and help them establish objective psychological expectations.
7.Pediatric or internal medicine assessment: Do a general physical examination and relevant auxiliary examinations.
8. Family conditions and rehabilitation conditions: Families who have received professional training or have regular guidance from a language training teacher can conduct auditory language training for the child at home; otherwise, the child should be sent to a rehabilitation school or institution for deaf children.
III. Preparation for auditory language rehabilitation
Patients, parents and teachers should be made aware of the importance of auditory language rehabilitation after cochlear implantation, especially how to prepare the child with pre-speech deafness for postoperative rehabilitation and the choice of rehabilitation site. Pre-operative rehabilitation should be implemented according to the age and hearing and language level of different children. The content of the rehabilitation training should focus on the establishment of auditory awareness and the understanding of the definition of things, so as to prepare the patient for the behavioral experience and learning psychology for the post-operative start-up and rehabilitation training.