Cochlear implantation is a new technology in the field of medicine and rehabilitation and is constantly being updated as technology evolves. Therefore, there is a need for guidelines in the selection of indications, preoperative evaluation, surgery, postoperative tuning and auditory speech rehabilitation.
Cochlear implantation involves many fields of medicine, audiology, biomedical engineering, education, psychology and sociology, and requires a team of physicians, audiologists, speech-language pathologists, speech therapists, rehabilitation teachers, engineers and parents to work together.
Selection of Indications
I. Patient selection criteria
Cochlear implantation is mainly used to treat severe or very severe sensorineural deafness in both ears.
1. Selection criteria for patients with prespeech deafness.
①The age of implantation is usually 12 months – 6 years. The younger the age of implantation, the better the results, but special precautions should be taken to prevent complications such as anesthesia accidents, excessive blood loss, and injury to the facial nerve inside and outside the temporal bone. Cochlear implants are not recommended for children younger than 6 months of age, but early surgery is recommended for children or adolescents over 6 years of age who are at risk of cochlear osseointegration due to meningitis, and who have a history of hearing aid wear and auditory speech rehabilitation since childhood.
② Severe or very severe sensorineural deafness in both ears. After comprehensive audiological evaluation, children with severe deafness who have been wearing hearing aids for 3-6 months and have no or unsatisfactory results should undergo cochlear implantation; children with profound deafness can be considered for direct cochlear implantation.
③No contraindication to surgery.
④Guardians and/or the implant recipient have a correct understanding of cochlear implantation and appropriate expectations.
⑤ The conditions for auditory-speech rehabilitation education are available.
2. Selection criteria for patients with postlingual deafness.
①Patients of all ages with postlingual deafness.
②Severe or very severe sensorineural deafness in both ears, unable to communicate with normal auditory speech by hearing aids.
③No contraindication to surgery.
④The implant recipient and/or guardian has a correct understanding and appropriate expectation of cochlear implantation.
Contraindications to surgery
1. Absolute contraindications: severe malformation of the inner ear, such as Michel’s malformation; absence or interruption of the auditory nerve; acute purulent inflammation of the middle ear mastoid.
2. Relative contraindications: frequent seizures that cannot be controlled; severe mental, intellectual, behavioral and psychological disorders, and inability to cooperate with auditory speech training.
Suggestions for clinical practice of cochlear implantation in special cases
1. Cerebral white matter lesions: Also known as cerebral white matter dystrophy, it is a group of lesions mainly involving the white matter of the central nervous system, characterized by abnormal development or diffuse damage to the myelin sheath of the central white matter.
If white matter lesions are found on MRI, intellectual and neurological signs and MRI review are required. If there is no regression in intelligence or motor development, if all system functions are basically normal except hearing and speech, if there is no positive cone bundle sign or no change in sign in neurological examination, and if there is no high signal in the white matter lesion area (DWI image) in MRI; and if the lesion does not expand under dynamic observation (interval > 6 months), cochlear implantation can be considered.
2. Auditory neuropathy (auditory neuropathy spectrum disorder): It is a special kind of neurological deafness caused by malfunction of the inner hair cells, auditory nerve synapses and/or the auditory nerve itself. It is typically characterized by normal otoacoustic emissions (OAE) and/or cochlear microtonal potentials (CM) and absent or severely abnormal auditory brainstem responses (ABR).
Currently, cochlear implants are effective in improving hearing in most patients with auditory neuropathy, but some patients may not be effective or may have poorer outcomes, so the patient and/or guardian must be informed of the risks prior to surgery.
3. Bilateral cochlear implants: Bilateral implants can improve sound source localization, speech understanding in quiet and background noise, help to obtain a more natural sound perception, and promote the development of auditory speech and music appreciation. Bilateral implantation or sequential implantation can be chosen. The shorter the interval between two surgical procedures, the better the postoperative speech rehabilitation.
4. Cochlear implantation for people with residual hearing: People with residual hearing, especially those with high-frequency steep-drop hearing loss, are suitable for electrode implantation that preserves residual hearing, and can choose the combined acoustic and electrical stimulation mode after surgery.
5. Cochlear implantation in patients with structural abnormalities of the inner ear: Structural abnormalities of the inner ear associated with cochlear implantation include common cavity malformation, cochlear dysplasia, cochlear ossification, narrowing of the internal auditory canal, etc. Cochlear implantation can be performed in most patients, but preoperative case discussions should be organized, intraoperative management should be cautious, and facial nerve monitoring is recommended. Postoperative results vary greatly among individuals.
6. Cochlear implantation for chronic otitis media with tympanic membrane perforation: If the inflammatory response of chronic otitis media with tympanic membrane perforation is under control, one stage or staged surgery can be chosen. One-stage surgery means that cochlear implantation is performed at the same time as the eradication of middle ear mastoid lesions and tympanic membrane repair (or mastoid cavity autologous tissue filling and external ear canal closure); staged surgery means that the lesions are removed first, the tympanic membrane perforation is repaired or the external ear canal is closed, and cochlear implantation is performed 3-6 months later.
Pre-operative evaluation
I. Medical history taking
The medical history is taken to understand the possible causes of the disease. The otologic history should focus on the etiology and pathogenesis of the hearing loss and should include a history of hearing, tinnitus and vertigo, ototoxic drug exposure, noise exposure, systemic acute and chronic infections, past otologic history, family history of hearing loss, hearing aid wear, developmental factors (systemic or local developmental abnormalities, mental development, etc.), and other etiologies (e.g., epilepsy and psychiatric conditions).
Children with hearing loss should also include maternal pregnancy history, birth history, pediatric growth history, and speech development history. The patient’s speech-language abilities (e.g., articulation clarity, comprehension, expression, etc.) and desire to improve communication should also be understood.
Ear examination
This includes the auricle, external auditory canal and tympanic membrane.
Audiology and vestibular function examination
(A) Examination items
1. Pure tone audiometry: including air and bone conduction thresholds; pediatric behavioral audiometry can be used for children 6 years old and younger, including behavioral observation, visual reinforcement audiometry and play audiometry.
2.Acoustic conductance: including tympanogram and stapedius muscle reflex.
Auditory evoked potentials: including ABR, 40 Hz auditory event-related potentials or auditory steady-state response (ASSR), and cochlear microtonal potentials.
4. Otoacoustic emissions: aberration product otoacoustic emissions or transient evoked otoacoustic emissions.
5.Speech audiometry: Speech recognition rate and speech recognition threshold tests are available, and appropriate open-ended and/or closed-ended speech test materials are selected according to the patient’s age and speech perception level (Appendix 1).
6.Hearing aid effect assessment: hearing aid threshold test and/or speech recognition test after optimal matching of hearing aids.
7.Vestibular function test (for those who have a history of vertigo and can cooperate with the test).
8.Electrical stimulation test of drum head (if necessary).
(B) Audiological inclusion criteria
1.Patients with prelingual deafness: subjective and objective comprehensive audiological assessment is required. Objective audiological assessment: short sound ABR response threshold >90 dBnHL, 40 Hz auditory event-related potential below 1 kHz response threshold >100 dBnHL, auditory steady-state response 2 kHz and above frequency threshold >90 dBnHL; otoacoustic emissions fail in both ears (except for patients with auditory neuropathy).
Subjective audiological assessment: average threshold in bare ear > 80 dBHL for behavioral audiometry; hearing threshold > 50 dBHL for frequencies above 2 kHz; speech recognition (closed bisyllabic words) score ≤ 70% after hearing aid, for those who cannot cooperate with speech audiometry, confirmed by behavioral observation that they cannot benefit from hearing aid.
2.Patients with post-speech deafness: very severe hearing loss with pure tone air-conduction mean hearing threshold > 80 dBHL in both ears; severe hearing loss with open phrase recognition < 70% in the better hearing ear after hearing aid.
3. Residual hearing: patients with better hearing at low frequencies but hearing thresholds >80 dBHL at 2 kHz and above, and whose communication needs cannot be met with hearing aids, are eligible for cochlear implantation; for patients who cannot detect any residual hearing, the risk of poor postoperative auditory rehabilitation should be explained to the patient or guardian.
Imaging evaluation
A thin-layer CT scan of the temporal bone, MRI of the inner ear and skull are routinely performed, and 3D reconstruction of the cochlea is performed if necessary.
V. Speech and language Speech and language ability assessment
For patients with certain language experience or ability, speech and language ability assessment can be done. For infants and toddlers younger than 3 years old who are unable to cooperate, “parent-child play” video observation and questionnaires can be used for assessment.
VI. Assessment of children’s psychological, intellectual and learning abilities
Children over 3 years of age can be assessed by the H. H. Nei Learning Ability Test (Chinese Deafness Test). Children under 3 years of age can use the Graflex Mental Developmental Behavior Inventory (MDSCI). For children with suspected mental retardation (IQ < 67 on the Greek-Internal Learning Ability Assessment and mental developmental quotient < 70 on the Greifers Test) or abnormal mental behavior, further observation, diagnosis and identification at a professional institution are recommended.
For children with non-socio-cultural mental retardation, ADHD, autism and other mental retardation, parents should be informed of the difficulties that these disorders may bring to post-operative rehabilitation, and parents should be helped to establish objective and reasonable psychological expectations.
Pediatric or internal medicine evaluation
Perform a general physical examination and relevant auxiliary examinations.
Evaluation of family and rehabilitation conditions
The patient and/or guardians and teachers should be made aware of the importance of auditory speech rehabilitation after cochlear implantation, and the patient and/or guardians should be helped to establish correct expectations and to prepare for the postoperative rehabilitation training and the choice of rehabilitation site for the child with prelingual deafness, so that scientific rehabilitation placement can be carried out reasonably.
Cochlear implant surgery
I. Requirements for the surgeon
The surgeon should have rich experience in middle ear mastoid surgery and have attended systematic professional training in cochlear implant surgery, and should have performed more than 20 cochlear implant surgeries independently under the guidance of an experienced surgeon.
Requirements for the operating room and basic equipment
The operating room should be equipped with good sterile surgical conditions, an operating microscope, an otologic drill and other related equipment.
Pre-operative preparation
The preoperative conversation should be conducted by the surgeon and the audiologist so that the patient and/or the guardian fully understand the possible risks and complications of the surgery, the benefits and risks associated with cochlear implantation, and sign the informed consent form for the surgery (Annex 2).
Cochlear implant surgery is a Class II incision, and antibiotics should be used routinely during the perioperative period, and surgical preparation, general anesthesia preparation and preoperative medication should be the same as other surgeries.
IV. Operation steps and methods
The cochlear implant surgery is performed through a retroauricular incision, a transmural saphenous approach, a cochlear window or a round window approach, and the specific operation can be performed according to the requirements of each type of cochlear implant.
V. Intraoperative monitoring
Electrode impedance testing and electrically evoked nerve response testing are performed according to the cochlear implant device used to understand the integrity of the electrodes and the response of the auditory nerve to electrical stimulation.
VI. Post-operative treatment
Post-operative imaging is performed to determine the position of the electrodes, and the rest is the same as general otologic surgery.
Complications of surgery
Common complications include tympanic membrane perforation, external ear canal injury, abnormal taste, vertigo, tinnitus, facial muscle twitching or pain, infection, scalp hematoma, cerebrospinal fluid leakage, facial nerve palsy, meningitis, intracranial hematoma, body implant displacement or dislocation, skin flap necrosis, etc., which should be handled actively according to the corresponding situation.
VIII. Power on and commissioning
Usually, the machine is turned on 1-4 weeks after surgery, and the machine is usually adjusted 1-2 times within the first month after the machine is turned on, after which the time is arranged according to the patient’s condition, and the adjustment interval is extended appropriately after the hearing is stabilized, and finally the machine is adjusted once a year. The start-up and adjustment methods and procedures can be performed according to the technical requirements of each product. If the contralateral ear can benefit from a hearing aid, it is recommended that the hearing aid be fitted as early as possible.
Requirements for the audiologist: A good basic knowledge of audiology and cochlear implants with professional training is required. Commissioning of infants and children should be done by experienced audiologists.
IX. Evaluation of surgical results
Successful surgery should include the following aspects.
① Good healing of the incision.
② Imaging examination and correct position of electrode implantation.
③Patients have subjective or objective auditory response after power on and commissioning.
Post-implant auditory speech rehabilitation
Cochlear implant patients must undergo scientific auditory speech rehabilitation after surgery. Through scientific and effective auditory speech rehabilitation training, patients can develop and improve their perceptual listening, discriminative listening, and comprehension listening skills, and promote the development of speech comprehension, speech expression, and language use.
Pre-speech deaf patients need to develop a systematic auditory speech rehabilitation program, while focusing on the development of Xin language skills and good listening habits, to improve their auditory speech communication skills, and to promote overall physical and mental development. For the post-language deaf patients, we focus on auditory adaptation and speech recognition training.
I. Rehabilitation goals
1. The formulation of rehabilitation goals should be based on the staged rehabilitation assessment.
2. The content of rehabilitation goals should cover auditory, speech, language, cognition and communication.
3. The formulation of rehabilitation goals should be clear, specific and observable.
II. Rehabilitation Model
Parents or guardians of children with cochlear implants should acquire the necessary knowledge and skills of auditory speech rehabilitation under the professional guidance of the rehabilitation institution, take the initiative to practice, and strive to become the supporter, guide and accompanist of the whole process of rehabilitation education for children with hearing impairment, so as to achieve the maximum rehabilitation effect. Adult cochlear implant recipients can receive auditory adaptation training and speech recognition training guidance at designated rehabilitation institutions according to their doctors’ recommendations.
Institutional rehabilitation: Children with cochlear implants can receive full-time preschool rehabilitation education, auditory management and individual intensive training for auditory speech rehabilitation at rehabilitation institutions.
2. Community-based family rehabilitation: Children with low-level cochlear implants can choose to be guided by an institution and receive auditory speech rehabilitation training in the form of parent-child training, single training by appointment, and home-guided hourly service.
3. Attending classes: Children with cochlear implants who have some auditory speech ability are encouraged to attend ordinary kindergartens and schools.
Rehabilitation principles
1. Insist on continuous hearing management, regular evaluation of the rehabilitation effect of cochlear implants and daily morning checkups to ensure that the listening effect is in an optimal state.
2. Provide standardized rehabilitation facilities, optimize the acoustic environment, and create excellent listening conditions.
3. Emphasize “listening as the main focus”, establish the advantages of the auditory center, and reasonably apply visual and tactile aids to achieve the auditory training goal of perceiving, discriminating, recognizing and understanding sounds.
4. Follow the rules of language acquisition for children, start with speech comprehension, try to combine with daily life situations, and focus on developing language use skills.
In the process of language learning, we pay attention to the problems in speech production – breathing, articulation and phonology – and correct them in order to improve speech intelligibility.
6.Adhere to the rehabilitation assessment-oriented, diagnostic teaching methods, to achieve personalized services for auditory speech rehabilitation training.
7. Insist on the concept of comprehensive rehabilitation, integrating the five major developmental fields of preschool children, such as health, science, language, art and society, to promote the comprehensive development of children with cochlear implants.
IV. Rehabilitation Assessment
1. Assessment of the sound field of the implanted ear: Through the hearing threshold test after hearing reconstruction, we can understand the hearing sensitivity of each frequency after hearing reconstruction. The test frequencies include 0, 5, 1, 2 and 4 kHz.
2. Speech-Language Auditory Ability Assessment: The auditory speech recognition of cochlear implant recipients is used to evaluate their auditory ability in order to understand the processing of the auditory center and the whole process of auditory pathways. The content includes tests of tone recognition, vowel recognition, rhyme recognition, bisyllabic word recognition, phrase recognition, etc.
3.Language ability assessment: Through the assessment of speech articulation level, comprehension, expression, usage and grammatical ability of children with cochlear implants, the level of language development and the corresponding language age can be known, which can be used as a basis to understand the rehabilitation effect, determine the starting point of language learning, clarify the language development goal and formulate the rehabilitation plan.
4. Questionnaire assessment: For children with cochlear implants whose speech and language skills are not yet sufficient to complete the above auditory, speech and language assessments, parents or teachers who are in close contact with the child may be interviewed to complete a questionnaire assessment.
Recommended questionnaires: Meaningful Auditory Integration Scale (MAIS), Infant and Toddler Meaningful Auditory Integration Scale (IT-MAIS); Parent Evaluation of Child’s Auditory Performance (PEACH), Teacher Evaluation of Child’s Auditory Performance (TEACH); Meaningful Use of Speech Scale (MUSS); Mandarin Child Vocabulary Development Inventory (MCDI). For long-term outcomes in large samples, the Auditory Ability Rating Questionnaire (CAP) and Speech Intelligibility Rating Questionnaire (SIR) can be used to assess the auditory perception and verbal ability of the implant recipient, respectively.
The Nijmegen Cochlear Implantation Inventory (NCIQ) is recommended for the assessment of quality of life before and after cochlear implantation.