What Is the Difference Between a Cochlear Implant and a Hearing Aid?

A cochlear implant is an electronic device that converts sound into an electrical signal in a certain coded form by an external speech processor, and directly excites the auditory nerve through an electrode system implanted in the body to restore or reconstruct the hearing function of the deaf. In recent years, with the development of electronic technology, computer technology, phonetics, electrophysiology, materials science, and ear microsurgery, cochlear implants have entered clinical applications from experimental research. Cochlear implants are now routinely used worldwide to treat severe to total deafness.

Basic Information

English name: cochlearimplant; artificialcochlear; electroniccochlearimplant

Visiting department: Otorhinolaryngology
Contagious: no

Cochlear implant history and current status

A cochlear implant is an electronic device that converts sound into an electrical signal in a certain coded form by an external speech processor, and directly excites the auditory nerve through an electrode system implanted in the body to restore, improve and reconstruct the hearing function of the deaf. Over the past two decades, with the development of high technology, cochlear implants have made rapid progress and have entered clinical applications from experimental research. Cochlear implants are now routinely used worldwide to treat severe to total deafness. Cochlear implant is currently the most successful biomedical engineering device.

The history of cochlear implants can be traced back to 1800 Italy Volta found that electrical stimulation of normal ears can produce hearing. In 1957, France's Djourno and Eyries first implanted electrodes into the cochlea of a deaf patient, so that the patient could sense the sound of ambient sound. In the 1960s and 1970s, scientists in Europe, America and other countries also successfully restored hearing to deaf patients through electrical stimulation. Through the study of human and animal models, it was found that the characteristics of hearing induced by electrical stimulation and problems to be solved, such as: narrow dynamic range, steep increase in loudness, and poor threshold tone recognition. 1972 American House-3M single-channel cochlear implant becomes the first commercialized device. There were more than 1,000 users from 1972 to the mid-1980s. 1982 Australian Nucleus 22 cochlear implant passed FDA approval, becoming the first multi-channel cochlear device used worldwide. The major cochlear companies in the world now are Cochlear in Australia, MedEl in Austria and AB in the United States. By the beginning of 2010, more than 100,000 deaf people worldwide had used cochlear implants, and more than half of them were children.

Multi-channel cochlear implantation has begun in China in 1995, and this technology has been relatively mature. With the development of cochlear implantation, the number of cases has increased and the scope of indications has expanded. The efficacy and safety of cochlear implantation in deaf cases with special indications have also been confirmed, making the adaptation of cochlear implantation The certificate is further expanded. For example: cochlear implantation in patients with no residual hearing before surgery; cochlear implantation in cases of inner ear deformities and cochlear ossification; cochlear implantation in patients with chronic otitis media; cochlear implantation in young deaf patients; deafness in advanced age Cochlear implant in the patient.

To obtain a normal language, humans not only need normal hearing, but also the normal development of the auditory language center. This is why even if adults with prelingual deafness are implanted with cochlear implants, they can hear the sound, but they cannot understand the language and speech. Studies have shown that the human auditory and speech center develops around 5 years of age. Adults who are deaf before speech develop deafness before language development, lose the opportunity for normal development of the auditory and speech center, and lose the plasticity of their auditory and speech center. Therefore, even if these patients receive cochlear implants, they can only hear sounds and cannot obtain normal language. The best implantation age for prelingually deaf patients is before 5 years.

For adults with post-speech deafness, the cause of their deafness may be sudden deafness, drug-induced deafness, or hereditary delayed deafness (large vestibular aqueduct syndrome) based on congenital inner ear malformations. Before these adult deaf patients, they had normal hearing and acquired normal language, and their auditory language center was fully developed. Therefore, these deaf patients are called adult deaf patients. Adults with post-speech deafness are one of the best indications for cochlear implantation. The auditory language center of this type of deafness patients has developed normally before deafness. After receiving cochlear implantation, they have regained their hearing and can Awakening their past memory of language, so these patients are able to restore language ability in a short time. For adults with post-speech deafness, an important issue is that cochlear implantation as early as possible after deafness will quickly evoke their past memory of the language and obtain better language effects. If deafness is long, the patient's memory of past language will be forgotten, resulting in a decrease in the effectiveness of cochlear implantation. At present, the problem of cochlear implantation in elderly deaf patients is receiving more and more attention. Most of the elderly deaf patients are post-speech deaf patients. In addition to the above reasons, their deafness is more due to senile progressive hearing loss until Use of hearing aids does not work. With the development of society and economy, the life expectancy of the population has been extended, and the quality of life of the elderly has also received more attention from society and families. Restoring the auditory language ability of the elderly can improve their language communication ability, improve their psychological state, enable the elderly to gain self-confidence, and greatly improve their quality of life. Elderly deaf patients can get good hearing and speech after receiving cochlear implants. In fact, this work has already been carried out in the United States and Europe. For example, at the Cochlear Implant Center of the University of Iowa Hospital in the United States, a considerable part of cochlear implanters are elderly deaf patients. The communication ability has been greatly improved. For example, they did not dare to drive before the cochlear implantation, but after receiving the cochlear implantation, they can drive to supermarkets and hospitals by themselves.

Cochlear implant speech processing solution

At the end of the 1970s, the University of Utah developed the first multi-channel cochlear implant device that became a commodity. Its voice processor divides the sound into 4 different channels, and then compresses the analog signal output from each channel to adapt to the narrow electrical stimulation. Small dynamic range. This speech processing scheme is called analog compression (CA).

In the early 1980s, the University of Melbourne, Australia developed a Nucleus cochlear implant device with 22 intra-snail electrodes. The design idea of Nucleus' speech processor is to extract important speech features, such as the fundamental frequency and formants, and then pass them to the corresponding electrodes by encoding. The Nucleus processor is characterized by bi-phase pulses, bipolar stimulation, stimulating different electrodes in a time-sharing manner, and the stimulation frequency does not exceed 500 Hz. The speech processing solution from the initial extraction of only the fundamental frequency and the second formant (F0F2) information, to the WSP processor (F0F1F2) with the first formant, F0F1F2 plus the multipeak processor with three high-frequency peaks (multipeak), To date, only a peakpeak processor that extracts any of the 6 highest energy frequency information in 22 analysis bands.

The continuous interval sampling (CIS) speech processor studied by Wilson et al. Contrary to Nucleus's feature extraction design philosophy, the CIS processor tries to preserve the original information in the speech, divides the speech into 4 to 8 frequency bands and extracts the waveform envelope information of each frequency band, and then uses the logarithmic function to perform dynamic range compression, and uses high The frequency bi-phase pulse continuously samples the compressed envelope, and finally sends the burst with the speech envelope information to the corresponding electrodes at intervals. From the perspective of information content, CIS and CA processors are basically the same, but the advantage of CIS is that it avoids the electric field interference caused by the simultaneous stimulation of multiple electrodes. Although CIS and Nucleu both use biphasic pulse interval stimulation, they have the following two differences: First, each electrode of the CIS uses a high-frequency (800-2000Hz) pulse train for constant and continuous stimulation, even if The same is true when there is no sound, except that the pulse amplitude drops to a threshold level. Second, the analysis frequency band of CIS and the number of stimulation electrodes are the same. At present, the CIS speech processing scheme has been widely adopted by most cochlear implant companies in the world, and based on this New improvements have been made. For example, the American ABC company introduced the S series processing solution, the Australian Nucleus company introduced the CI24M 24-channel device ACE solution and the Austrian MEDEL company introduced the fast CIS solution.

Indications for cochlear implantation

Pre-speech deaf patient

(1) The hearing loss range of children with severe or extremely severe sensorineural hearing loss in both ears is 1 kHz and higher, and the hearing threshold is above 90 dB. For those who have no residual hearing before surgery, a hearing aid sound field audiometry is needed to help determine the residual hearing and, if necessary, an electrical stimulation auditory brainstem evoked potential (EABR) test.

(2) The etiology is unknown, congenital, hereditary, medicinal, hearing loss after meningitis, and the lesion is localized in the cochlea; in patients with acoustic neuropathy, the lesion is localized in the cochlea, and preoperative EABR examination is required to estimate the lesion site. From the medical point of view, the risk of hearing neuropathy needs to be informed to the parents of the child. For most inner ear malformations, including Mondini malformations, common cavity malformations, and large vestibular aqueduct malformations are still indications for cochlear implantation, parents of children need to be informed of the particular risks and parents have reasonable expectations.

(3) Time of deafness For newly occurring hearing loss, it is necessary to observe stable hearing changes for at least 3 months.

(4) The optimal age should be 12 months to 5 years; subject to the limitations of brain hearing and speech plasticity, cochlear implants should be implanted as soon as possible.

Children or adolescents over 5 years of age need a certain listening and language foundation, and a history of hearing aid wearing and hearing or language training from an early age. Hearing aids are ineffective or perform poorly, meaning that the open sentence recognition rate is 30% or the two-word recognition rate is 70% under the best hearing-aid listening environment.

(5) No significant improvement in hearing ability after the selection of hearing aids. Wear appropriate hearing aids, and no significant improvement in hearing and language skills after 3 to 6 months of hearing rehabilitation training.

(6) Have normal mental and intellectual development.

(7) The family and / or implanter have a correct understanding and appropriate expectations of the cochlear implant.

(8) Conditions for hearing and speech rehabilitation education.

(9) No contraindications to surgery.

2. Post-speech deaf patients

(1) Hearing loss in adults with binaural severe or very severe sensorineural hearing loss ranges from 1 kHz and higher and the hearing threshold is above 70 dB. For those who have no residual hearing before the operation, a hearing aid sound field audiometry is needed to help determine the residual hearing, and if necessary, an EABR examination or a psychophysical test of the drum-point electrical stimulation is performed.

(2) Candidates for elderly cochlear implantation in post-deaf deaf patients of all ages need to have a correct understanding of cochlear implants and appropriate expectations.

(3) Time of deafness For newly occurring hearing loss, it is necessary to observe stable hearing changes for at least 3 months.

(4) There was no significant improvement in speech recognition after hearing aids were selected.

(5) Have normal psychological and mental conditions, and patients have a correct understanding of cochlear implants and appropriate expectations.

(6) No contraindications to surgery.

Contraindications for cochlear implantation

Absolute contraindication

(1) Cases of severe inner ear malformation, such as Michel malformation or cochlea absent;

(2) The absence of the auditory nerve;

(3) severe mental illness;

(4) Pyogenic inflammation of the mastoid process in the middle ear has not been controlled.

2. Relative contraindications

(1) The general condition of the whole body caused by the accompanying disease is poor.

(2) Uncontrolled epilepsy.

(3) Patients with white matter lesions are not contraindications for cochlear implantation, but the parents of the child must be informed of the special risks and the parents have reasonable expectations.

(4) Secretory otitis media and gum ears are not contraindications to surgery. For patients with chronic otitis media and perforation of the tympanic membrane, if the inflammation is controlled, one-stage or staged surgery can be selected.

Cochlear Implant Evaluation

1. Medical history collection

Understand the cause through history collection and examination. The collection of otological history should focus on the causes and processes of deafness, and the patient's hearing history, tinnitus and vertigo history, history of ototoxic drug exposure, history of noise exposure, history of systemic acute and chronic infections, past history of ear diseases, Developmental factors (general or local malformation, mental development, etc.), family history of deafness, hearing aid wearing history, and other causes, such as epilepsy, mental condition, etc. Deaf children should also include: mother's pregnancy history, pediatric birth history, pediatric growth history, speech development history, and so on.

You should also understand the patient's language skills (such as pronunciation characteristics, articulation intelligibility) and language understanding and communication skills (such as oral, lip reading, sign language, written, guessing, etc.).

2. Otology examination

Including ear Guo, external ear canal, tympanic membrane and eustachian tube.

(1) Audiological examination Subjective hearing threshold measurement Pediatric behavior audiometry, including behavioral observation audiometry, visual enhanced audiometry and game audiometry, can be used in children under 6 years of age; Acoustic impedance measurement includes tympanic pressure curve and Sacral muscle reflex; auditory brainstem response (ABR) 40Hz-related potential (or multi-frequency steady-state evoked potential); otoacoustic emissions (transiently induced otoacoustic emissions or distortion otoacoustic emissions) ; Speech hearing threshold test is speech perception threshold and speech recognition threshold; speech recognition test includes speech test vocabulary and pediatric speech test vocabulary; Hearing aids must be equipped with professional hearing aids for hearing aids, usually with both ears worn, optional Hearing aid hearing threshold test and speech recognition test will be followed, followed by auditory language training for 3 to 6 months; vestibular function test (those with a history of vertigo); Drum Cape electrical stimulation test test including threshold, dynamic range, frequency discrimination, Psychophysical examinations such as interval discrimination and time discrimination.

(2) Evaluation criteria of audiology The pure-tone air conduction threshold of post-speech deaf patients is > 80dBHL (average value of 0.5, 1, 2, and 4kHz, WHO standard). If good ears help open sentence recognition less than 30%, and hearing loss is greater than or equal to 75dB, you can consider using cochlear implants [see US Food and Drug Administration (FDA) supplementary standards]; pre-speech deaf patients For infants and young children, a number of guest observations and behavioral assessments are required to conduct a comprehensive evaluation, including: no auditory response (120dBSPL) when ABR checks the acoustic output; no response when the maximum acoustic output is above 2kHz at a frequency of 40Hz related potential detection, below 1kHz Frequency> 100dB; Multi-frequency steady-state audiometry above 2kHz has no response at 105dBHL; distortion products otoacoustic emissions have no response at both frequencies; helpful for sound field audiometry above 2kHz, the hearing threshold does not enter the auditory language area (banana chart), speech The recognition rate (two-word) score is less than 70%, confirming that the child cannot get effective help from the hearing aid; For patients without any residual hearing, such as those with a clear hearing response to the electric stimulation of the drums, can still consider cochlear implantation surgery. If there is no auditory response to Gushen electrical stimulation, the patient or parent should be informed, and the patient and family should consider the risk of surgery.

3. Imaging evaluation

Imaging examination is the most important examination for patients. Thin-layer CT scan of the temporal bone, three-dimensional reconstruction of the cochlea, and magnetic resonance examination of the inner ear canal should be routinely performed, and skull magnetic resonance examination should be performed if necessary.

4. Language proficiency assessment

Speech proficiency assessment (language structure and function) should be performed on patients with certain language experience or ability, including speech intelligibility, vocabulary, comprehension ability, grammatical ability, expression ability and communication ability; for children under 3 years old and uncooperative , The method of video observation of "parent-child games" was used to evaluate, so as to judge the current language ability of patients.

5. Psychological, intellectual and learning ability assessment

For children over 3 years of age who lack language skills, the Hines Learning Ability Test can be selected, and for those under 3 years of age, the Griffith Mental Developmental Behavior Test can be used. Patients with suspected mental retardation (Hine's learning ability assessment IQ <68 points, Griffith test mental development quotient <70 points) or patients with abnormal psychological behavior should be advised to go to an authoritative institution for further observation, diagnosis and Identification. Cochlear implants may be considered for those with socio-cultural mental retardation; for patients with socio-cultural retardation, or with ADHD, autism, and other mental and intellectual developmental disorders, parents should be made aware that such diseases may provide patients with postoperative rehabilitation It brings great difficulties to help parents establish objective psychological expectations.

6. Pediatric or internal medicine assessment

Get a full physical examination and related auxiliary examinations.

7. Evaluation of family and rehabilitation conditions

Families who have received professional training or are regularly instructed by a language training teacher can conduct hearing and language training for children at home, otherwise they should be sent to a deaf rehabilitation school or institution.

Cochlear implant surgery

General anesthesia was used for surgery, and intravenous drip antibiotics were given before the incision. Electrode impedance testing and nerve response telemetry (NRT) were performed after the electrodes were implanted. Special cases such as inner ear malformation use EBAR monitoring and facial nerve monitoring. Facial crypt approach is mostly adopted in the surgical approach. Behind the ear is generally used. The incision is divided into two layers, the surface layer is the skin and subcutaneous tissue, and the deep layer is the temporal fascia and periosteal flap. The entire flap is turned back, exposing the cortex of the mastoid area. A receiver / stimulator bone bed was made on the skull surface above and behind the mastoid with an electric drill. A simple mastoidectomy was performed to expose the short anvil bones, which was used as a sign to open the recess of the face. The stimulator was placed into the bone bed, the stimulation electrode was inserted into the cochlear drum stage, and the reference electrode was placed on the surface of the skull below the temporal muscle. The cochlear deformity (such as Mondini deformity, common cavity deformity) and cochlear ossification cases should be modified accordingly. Surgical complications include wound infection, flap necrosis, facial paralysis, meningitis, and electrode prolapse. A small number of patients with cochlear implanted electrodes had mild vertigo after surgery and mostly disappeared within a few days.

Cochlear implant adjustment

Switch-on was performed one month after cochlear implantation. Due to different design principles of different cochlear implants, the tuning hardware and software used are different, and the tuning method, tuning process and tuning parameters are also different. Cochlear implants include implants in the body and speech processors outside the body. Mapping (mapping) is the process of adjusting the parameters in each cochlear implant device by a professional through a computer and special equipment to provide the patient with the most comfortable and effective stimulation and allow the patient to hear various sounds comfortably. Unless a professional sets appropriate values in a series of parameters through tuning, the speech processor will not work. The parameters that need to be adjusted after cochlear implantation include: speech coding schemes such as SPEAK, CIS, and ACE schemes; electrical stimulation modes, including unipolar stimulation, bipolar stimulation, and common ground mode; the channels used can be selected from 1 to 22 channels, the frequency distribution of the filtered output of the channel, the frequency range of 200Hz to 8kHz is assigned to each channel; the threshold value of each channel (the minimum stimulation level at which T value can produce auditory stimulation); the maximum comfortable stimulation of each channel (C Value for the greatest comfort stimulus the patient can feel).

The start-up is scheduled for 3 to 5 weeks after surgery. At this time, the internal part of the cochlear implant, especially the electrode part, is relatively stable. After turning on, most patients will have a gradual adaptation process to the external sound. After a period of psychological and physiological changes and development, they can stabilize. During the first 1 to 4 weeks after power-on, the electrode parameters have the largest and fastest changes. They are debugged once a week, once every two weeks in the second month, once a month in the third month, and every three months thereafter. Six months, once a year.

Cochlear hearing and speech rehabilitation

Patients, parents of deaf children and teachers should be made aware of the importance of auditory and speech rehabilitation training after cochlear implantation, especially how to prepare for postoperative deaf children and how to choose a rehabilitation location. Preoperative rehabilitation training should be implemented according to the characteristics of different children's age and hearing language level. The content of rehabilitation training should focus on the establishment of the patient's hearing consciousness and understanding of the concept definition of things. It should be used for postoperative commissioning and rehabilitation training. Good behavior experience and psychological preparation for learning.

The "Speaking Oral Training Method" is a logical and strict guiding principle. For children with cochlear implants, it refers to a training method that uses the signals of the cochlear implant to maximize the development of hearing and then develop oral language to create the best environment for them. Deaf children's hearing and speech training should conform to the language development law of children, and should be carried out gradually from shallow to deep according to the "hearing age" of deaf children. It is roughly divided into three stages, namely the auditory training stage, the vocabulary accumulation stage, and the language training stage.

Hearing training stage

The hearing training stage mainly uses the residual hearing of the deaf children to listen to various sounds, awakens their "sleeping state", and often gives stimulation, repeated training and repeated strengthening, so that the deaf children gradually adapt to the daily sounds and enter the sound society.

2. Vocabulary accumulation stage

The vocabulary accumulation stage is based on hearing training, supplemented by visual and other sensations to let them know more social things, combining what they see and touch with sound signals to form signals in their brains, so that they gradually understand the meaning of speech.

3. Language training phase

The language training stage is based on the accumulation of vocabulary. Deaf children are trained to speak more, from single words to short sentences, from simple to complex, from small to many. Gradually, they can understand the language of others, so that others can understand themselves. Language.

Cochlear implant rehabilitation should be implemented under the guidance of professionals, and service agencies that undertake professional rehabilitation guidance provide appropriate rehabilitation training models for hearing impaired children and families.