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
Patient selection criteria for cochlear implantation are available for those with severe or profound deafness in both ears and lesions localized and diagnosed in the cochlea.
1. Selection criteria for patients with prelingual deafness.
①Severe or profound sensorineural deafness in both ears;
②The best age should be 12 months to 5 years old;
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 should have a correct understanding of the cochlear implant and appropriate expectations;
(6) The condition of hearing and speech 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 post-deaf patients.
①Patients of all ages with postlingual deafness;
②Severe or very severe sensorineural deafness in both ears;
③ Ineffective or poor hearing aids, open phrase recognition rate ≤ 30%;
④No contraindication to surgery;
⑤ Have good psychological quality and initiative, correct understanding of the cochlear implant and appropriate expectations;
(6) Have family support. 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 results after surgery. In addition, the listening environment in life and work after surgery can also affect the outcome of cochlear implantation.
3. Contraindications to surgery.
Absolute contraindications include 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; and 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 rehabilitation training conditions. Secretory otitis media and glue ear are not contraindications to surgery. In chronic otitis media with tympanic membrane perforation, if the inflammation is controlled, one-stage or staged surgery can be chosen. One-stage surgery is to cure the middle ear mastoid lesion, repair the tympanic membrane (or fill the mastoid cavity with temporal muscle and close the external ear canal) and perform cochlear implantation at the same time. Staged surgery refers to the removal of the lesion, repair of the tympanic membrane perforation or closure of the external ear canal, followed by cochlear implantation 3 to 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 history of otology, 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.Otologic examination includes the auricle, external auditory canal, tympanic membrane and eustachian tube.
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;
③Auditorybrainstemresponse (ABR), 40Hz correlation potential (or multi-frequency steady-state evoked potential);
④Otoacoustic emissions (transient evoked otoacoustic emissions or aberration product otoacoustic emissions);
(⑤) Speech audiometry: speech hearing threshold test for language perception threshold and language 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 threshold test and speech recognition test should be done after matching, and then auditory language training should be conducted for 3 to 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 assessment criteria.
1. Patients with postlingual deafness: Binaural pure tone air conduction hearing threshold measurement > 80 dBHL (average of 0.5, 1, 2 and 4 kHz, WHO standard). 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 the Food and Drug Administration (FDA) supplemental criteria];
2. Patients with prelingual deafness: For infants and young children, a comprehensive assessment is required after several objective audiometric examinations and behavioral audiometry, including: no auditory response during ABR examination of acoustic output (120 dBSPL); no response during 40 Hz correlation potential detection of the loudest output at frequencies above 2 kHz and frequencies below 1 kHz > 100 dB; multi-frequency steady-state audiometry at frequencies above 2 kHz 105 dBHL No response;
The aberration product otoacoustic emission has no response in both ears at all frequencies; the hearing threshold does not enter the auditory language area (banana chart) at frequencies above 2kHz with a speech recognition rate (two-word words) score below 70%, confirming that the child cannot get effective help from the hearing aid;
3. For patients without any residual hearing, cochlear implantation can still be considered if there is a clear auditory response to electrical stimulation of the drum head. 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 risk of surgery.
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 clarity, vocabulary, comprehension, grammar, expression and communication ability; for children younger than 3 years old who are uncooperative, the method of “parent-child game” video observation should be used for evaluation. For children younger than 3 years old who were uncooperative, a video observation of parent-child play was used to evaluate the patient’s language ability at this stage.
6.Psychological, intellectual and learning ability assessment: For children over 3 years old who lack language ability, the Schnee Learning Ability Test is optional; for those under 3 years old, the Greifers Mental Developmental Behavior Assessment Scale is optional. 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 explained to their parents the great difficulties such disorders may bring to their post-operative rehabilitation, and parents should be helped to 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.
Preparation for auditory language rehabilitation should make patients, parents and teachers aware of the importance of post-operative auditory language rehabilitation after cochlear implantation, especially to prepare the child with prespeech deafness how to conduct post-operative rehabilitation and the choice of the rehabilitation site. Pre-operative rehabilitation training 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 them for the behavioral experience and learning psychology for the post-operative start-up and rehabilitation training.
Cochlear implant surgery
Requirements for the surgeon: Cochlear implantation is a delicate microscopic otologic procedure that requires the surgeon to implant the electrodes in the best position in the cochlea without damaging the electrodes or damaging the important tissues of the middle and inner ear. Deformities of the middle or inner ear are also frequently encountered during surgery. Therefore, the surgeon should have extensive experience in middle ear mastoid surgery and some specialized training in cochlear surgery. Before performing cochlear implant surgery independently, the surgeon should have completed 3 to 5 cochlear implant surgeries under the guidance of an experienced physician.
Requirements for the operating room and basic equipment: The operating room should have good sterile surgical conditions, the operating microscope should have a clear field of view and adequate lighting, and the surgical drill should work stably and be fully equipped with drill bits. A facial nerve monitor can be used in hospitals with conditions, which is more necessary in cases of congenital temporal bone developmental malformation, reoperation, and when the implantation is likely to damage the facial nerve.
Pre-operative preparation.
1. Pre-operative conversation: For patients and families who are suitable for and undergo cochlear implant surgery, the surgeon and audiologist should have a pre-operative conversation with them to make them fully understand the possible dangers and complications during the surgery, the benefits, shortcomings and drawbacks brought by the cochlear implant, especially to make them understand the possibility of long-term maintenance of the external device and failure of the internal device, and sign the informed consent form for the surgery.
2. The informed consent form for surgery is attached at the end of this document.
3.Surgical preparation, general anesthesia preparation and preoperative medication are the same as other surgeries.
The surgical procedures and methods are performed according to the operation manuals provided by the cochlear implant companies.
Intraoperative testing Electrode impedance testing and electrically evoked nerve response testing are performed according to the cochlear implantation device used to understand the integrity of the electrodes and the response of the auditory nerve to electrical stimulation.
Post-operative management is the same as for general otologic surgery.
Complications of surgery and management Common complications of cochlear implantation include: perforation of the eardrum or external auditory canal, bulbar nerve palsy, thick scalp that affects signal transmission, vertigo, facial muscle twitching or pain during electrical stimulation, severe infection of the incision, injury to the mastoid vessels or sigmoid sinus resulting in hemorrhage, cerebrospinal fluid leakage, facial nerve palsy, and meningitis.
General complications can be treated conservatively, and a small amount of subcutaneous hematoma can be absorbed by itself without special treatment. Larger hematomas can be aspirated by hematopuncture and bandaged with pressure. Infection of the middle ear usually does not affect the implanted device and can be controlled with conventional methods. Mild vertigo mostly disappears on its own within a few days, and antivertigo medication can be used as appropriate for more severe vertigo. Severe complications mostly require reoperation, such as facial nerve decompression, cerebrospinal fluid repair, cochlear implant replacement, etc. Facial muscle twitching and pain caused during unipolar electrical stimulation can be resolved by tuning the machine.
Surgery for special cases Special conditions such as enlarged vestibular canal, congenital anomalies of the cochlear canal, Mondini and common cavity (commoncavity) inner ear malformations, cochlear ossification, and other special cases can be performed for cochlear implantation in most cases, but should be handled with caution during surgery. In cases where an intraoperative blowout may occur, technical preparations should be made to repair and fill the leak before surgery.
In cases with bony defects in the inner ear canal, insertion of electrodes into the inner ear canal should be avoided to avoid facial nerve paralysis or poor postoperative results. Auditory neuropathy is currently difficult to diagnose clinically, but as long as the patient has residual hearing, a better result can generally be achieved after surgery; patients without residual hearing should undergo electrical stimulation testing of the tympanic capsule and should be carefully considered for surgery. In special cases, preoperative case discussion should be organized.