Indications for cochlear implantation (a) Patients with prelingual deafness 1. Severe or very severe sensorineural deafness in both ears and hearing loss in children with hearing thresholds above 90 dB at 1 khz and higher frequencies. For those without preoperative residual hearing, hearing aid sound field audiometry is required to help determine residual hearing and EABR examination if necessary; 2. Etiology: unknown cause, congenital, hereditary, pharmacological, post meningitis hearing loss with lesions localized in the cochlea; for patients with auditory neuropathy with lesions localized in the cochlea, preoperative EABR examination is required to estimate the lesion site, given the current medical Given the current limitations in the understanding of auditory neuropathy from a medical perspective, the parents of the child need to be informed of the special risks. For most inner ear malformations, including Mondini malformation, common cavity malformation, and large vestibular aqueduct malformation are still indications for cochlear implantation, and parents need to be informed of the special risks and that they have reasonable expectations; 3. Time of onset of deafness: for recent hearing loss, stable hearing changes need to be observed for at least 3 months; 4. Optimal age should be 12 months – 5 years. Limited by brain hearing and speech plasticity, cochlear implant should be implanted as early as possible. Children or adolescents older than 5 years old need to have some hearing and language foundation, history of hearing aid fitting and hearing or speech training since childhood. Ineffective or very poor hearing aid is defined as open phrase recognition rate ≤ 30% or two-word word recognition rate ≤ 70% in the best hearing aid listening environment(2). 5. No significant improvement in hearing ability after hearing aid fitting; no significant improvement in hearing and language ability after 3-6 months of hearing rehabilitation training with appropriate hearing aids; 6. Normal psycho-intellectual development; 7. No contraindication to surgery; 8. Correct understanding and appropriate expectation of the cochlear implant by the family and/or the implantee; 9. Conditions for hearing and language rehabilitation education. (2) Patients with postlingual deafness 1. Severe or very severe sensorineural deafness in both ears; hearing loss in the range of 1khz and higher frequencies in adults with a hearing threshold of 70dB or more. For those without preoperative residual hearing, hearing aid sound field audiometry is required to help determine residual hearing and, if necessary, EABR testing or psychophysical testing with electrical stimulation of the drum head; 2. Patients of all ages with postlingual deafness; senior cochlear implant candidates need to have a proper understanding of the cochlear implant and appropriate expectations; 3. Time of onset of deafness: for newly occurring hearing loss, observation is required No significant improvement in speech recognition ability after hearing aid selection; 5. Normal psychological and mental status and proper understanding and expectation of the cochlear implant; 6. No contraindication to surgery. Contraindications to cochlear implantation (a) Absolute contraindications 1. Severe deformities of the inner ear, such as Michel deformity or cochlear deficiency; 2. Hearing nerve deficiency; 3. Severe psychiatric diseases; 4. Middle ear mastoid inflammation not yet controlled. (ii) Relative contraindications 1. poor general condition; 2. uncontrollable epilepsy; 3. patients with cerebral white matter lesions are not contraindicated for cochlear implantation, but the parents of the child must be informed of the special risks and that the parents have reasonable expectations; 4. secretory otitis media and glue ear are not contraindications for surgery. In chronic otitis media with tympanic membrane perforation, if the inflammation is under control, a stage or staged surgery can be chosen.