Cochlear implantation is used for patients with severe hearing loss to make them regain their hearing. Cochlear implantation can be performed from 1 year of age. Preoperative evaluation is crucial for proper patient selection. Cochlear implants are more successful in younger patients and for patients who has hearing loss after the speech is learned.
Cochlear implants have two parts: the inner part which consists of the receiver and the cochlear electrodes, the outer part which consists of the external speech processor and the transmitter. The cochlear implant helps the hearing by providing electrical stimulation of the cochlear nerve in patients with severe hearing loss. The external processor of the cochlear implant receives sounds and converts them into electrical stimuli. These stimuli are transmitted as transcutaneous to the recipient and via the recipient to the electrodes in the cochlea. The electrical signals reached to the cochlear depolarizes the cochlear nerves, and enables the detection of sounds. Cochlear implant application is a team work where otolaryngologists, audiologists and speech pathologists work together.
The criteria that the childhood cochlear implant candidate should have:
- Children older than 12 months (1 year)
- Severe hearing loss
- Expectation to get more benefit from the hearing aid
- Family support, sufficient motivation, realistic expectations
- Providing rehabilitation and training support for speech and language development
Since patients will have general anesthesia, they should carry the appropriate health conditions for surgery and general anesthesia. Patients should be able to perform audiological evaluation.
* Adult patients with severe hearing loss who do not benefit from the hearing aid are candidates for cochlear implants.
Hearing levels of pediatric patients should be evaluated by ABR test. Information should be obtained from the family about children’s behavior against sound.
It is important whether the patient loses his hearing before or after language development. Since the patient’s previous meningitis may prevent the implantation of the cochlear implant, information should be obtained on this subject.
The presence of signs of middle ear infection such as holes and retraction in the eardrum should be detected. Has the patient had ear surgery before? It should be questioned. Active middle ear disease should be ruled out. In patients who have undergone an operation due to chronic middle ear disease, the cochlear implant can be inserted, but the operation becomes a little more difficult.
High resolution temporal bone tomography should be performed before all cochlear implant operations. With tomography, information can be obtained about the inner ear morphology, the cochlea, the position of the facial nerve, the size of the facial recess, the height of the jugular bubl, and the thickness of the parietal bone, especially in young children. In order for all electrodes to be inserted, the cochlea must be of normal structure and its turning must be monitored. Mondini malformation of the cochlea does not allow the placement of all the electrodes. However, it is not an obstacle for the implant. Previous meningitis may disrupt the structure of the cochlea with fibrosis and ossification, preventing electrode placement. Magnetic Resonance Imaging is helpful in assessing whether the candidates for cochlear implants have open cochlea after meningitis and the presence of the cochlear nerve. Imaging techniques are also important to evaluate the internal acoustic channel width.
Candidates with cochlear implants and audiometric examination with and without hearing aid help the assessment. Complete cochlear implant evaluation should be done by a trained audiologist.
A cochlear implant is a very good option in the treatment of severe hearing loss in patients with favorable expectations.
The cochlear implant is placed in the mastoid bone area behind the ear by surgery. For this, a mastoidectomy is performed. The facial recess zone opens between the outer ear canal and the facial nerve. A round window is observed from here. After the round window niche touring, a cocheostomy is performed and the electrodes are placed in the cochlea. It is placed adjacent to the mastoid cavity posterior to the recipient auricle. The surgical area is then closed. A few weeks after recovery, the outer part is placed, activated and adjusted.
Depending on the surgery, facial nerve palsy can be seen in 0.4%. Electrodes can be damaged by 1.2%. Tinnitus and dizziness can be seen after surgery, but then decrease. Rarely, meningitis can be seen. In this case, antibiotic treatment is given intravenously. If the implant does not work or beats, it must be placed again.
The postoperative anterior posterior x-ray can be used to check whether the electrodes are located in the cochlea. Dressing with mastoid dressing is applied to the mastoid area for compression. The wound area is checked with postoperative follow-up. Facial nerve functions are checked. After the operation, Magnetic Resonance Imaging cannot be performed without removing the internal magnet part of the receiver.
Vaccination should be done for pneumococcal and influenza to prevent meningitis. Antibiotic therapy should be given after surgery.
Programming of the electrodes can begin 2 weeks after the operation. However, programming is usually done in 4-5 weeks after adequate wound healing.
Today, cochlear implant application can be performed bilaterally simultaneously.