Who needs a cochlear implant? In general, cochlear implants are currently indicated for patients with severe or profound sensorineural deafness in both ears, meaning that the lesion causing the deafness is located in the synaptic portion of the cochlea or cochlear nerve (lesions that are truly located in the cochlear nerve or posterior nerve pathway may be less effective or ineffective). However, whether the hearing level is sufficient for cochlear implantation depends on whether there are contraindications that prevent or make it inappropriate. Therefore, in addition to the hearing examination, imaging, family situation, and intellectual and mental evaluations are needed.
1. Age requirements for cochlear implantation
The age requirement for cochlear implantation varies depending on when the deafness occurred. We classify deafness into pre-speech and post-speech deafness based on whether or not the deafness has learned language at the time of deafness.
The best age for prelingual deafness is 12 months to 6 years old, because the auditory and speech centers need to be stimulated by sound in order to develop, and the development of these centers is basically complete at the age of 6 (the critical period of brain plasticity), and after the age of 7 the development is very slow or does not change much, which is why there is an age limit for cochlear implants for prelingual deafness.
Children or adolescents older than 6 years of age need to have some hearing and language foundation, a history of hearing aid wear and a history of hearing or language training since childhood.
Cochlear implants can be done for postlingual deaf patients of all ages, provided that they are well evaluated before surgery, are in good general condition, and can tolerate about 2 hours of general anesthesia for cardiopulmonary function, etc.
2. Fitting of appropriate hearing aids.
After 3-6 months of hearing rehabilitation training, there is no significant improvement in auditory language ability; ineffective or very poor hearing aid is defined as open phrase recognition rate ≤ 30% or double word recognition rate ≤ 70% in the best hearing aid listening environment. Cochlear implantation is expensive, but of course, the most expensive is not the best, cochlear implantation is not a solution, but any hearing aid with good results may not consider cochlear implantation.
3. No contraindications to surgery.
Contraindications to surgery include
(1) Severe deformities of the inner ear, such as Micheal deformity, cochlear deformity, etc. There is no space for cochlear electrode placement. Such patients can only consider auditory brainstem implantation (ABI), which is not yet available in China.
(2) Hearing nerve (or cochlear nerve) deficiency, extreme narrowing of the internal auditory canal, or no auditory response on preoperative examination along with MRI water imaging of the internal auditory canal suggesting hypoplastic or undeveloped cochlear nerve; such patients can only be considered for auditory brainstem implantation.
(3) Severely mentally handicapped; those who cannot cooperate with language training; severe mental illness; those with acute or chronic inflammation of the middle ear mastoid that has not been cleared, and those with chronic otitis media with tympanic membrane perforation, if the inflammation is under control, they can opt for one-stage or staged surgery. One-stage surgery refers to radical treatment of middle ear mastoid lesions, tympanic membrane repair (or mastoid cavity temporal muscle filling and closure of external ear canal) and cochlear implantation at the same time. 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.
(4) Others. Relative contraindications include poor general condition, uncontrollable epilepsy, and lack of reliable rehabilitation. Secretory otitis media and glue ear are not contraindications to surgery.
4. The family and/or the implant recipient themselves have a correct understanding of the cochlear implant and appropriate expectations.
The majority of patients with cochlear implants around 1 year old have good results and can attend normal kindergartens and elementary schools and can communicate by telephone, but patients with prelingual deafness greater than 7 years old may have only auditory responses to positioning and can hear horns and fire alarms etc. for emergency evacuation, and may have crossed understanding for language, i.e. they can hear the sound of speech but cannot understand the content.
5. Conditions with auditory language rehabilitation education.
After cochlear implantation is equivalent to restarting access to sound and learning to speak again, it is necessary to strengthen auditory and speech training, and it is recommended to learn or master scientific rehabilitation methods in professional rehabilitation institutions.
6. Support from family.
In addition to financial support, mental support must be given, and then reinforcement of auditory and verbal communication with the patient is beneficial to rehabilitation.
7. 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 effect of cochlear implantation in different noisy and quiet environments, familiar environments and communication with people versus unfamiliar environments and people.
8. Potential indications for cochlear implantation.
(1) Patients with unilateral severe sensorineural deafness combined with severe tinnitus, which may improve hearing while having some masking or therapeutic effect on tinnitus.
(2) Unilateral severe or very severe sensorineural deafness. Bilateral hearing is superior to unilateral hearing, especially in sound source discrimination, speech recognition, etc.