The preoperative evaluation of a cochlear implant patient is very important and is the inevitable process by which the physician determines whether the deaf patient is suitable for cochlear implant intervention. To be eligible for cochlear implantation, the physician must first know the degree and nature of the deafness, whether the specific cause of the deafness can be identified, and what the patient’s general condition is. Can the patient tolerate the anesthesia and surgical procedure? Are there any contraindications to surgery?
Are there any other concomitant diseases that may affect the recovery outcome after cochlear implantation? The preoperative evaluation of cochlear implantation is very complex and extensive, so we will discuss each of the major tests below.
First of all, cochlear implantation is a method of auditory intervention for patients with more than severe sensorineural deafness, so the first thing is to conduct an audiological evaluation to understand the degree of deafness, its nature, and the degree of impact on speech and language ability, which includes the following.
I. Subjective hearing test
Adults and children who can cooperate with pure tone audiometry can provide the physician with basic information about the degree and nature of the patient’s deafness. Children who cannot cooperate with pure tone audiometry can use behavioral observation, visual reinforcement and play audiometry.
Objective hearing test
1. Acoustic conduction resistance (tympanogram and acoustic reflex): to understand the functional status of the middle ear. Patients who are suitable for cochlear implantation should have a type A or C tympanogram, which indicates that the middle ear function is normal or basically normal. Patients with cochlear implants should be unresponsive to acoustic reflexes because of the severe degree of deafness.
2. Auditory brainstem evoked potentials (ABR): For younger children who cannot cooperate with primary auditory observation, short sound ABR is the main method to understand the degree of their deafness. In addition, ABR in combination with other tests can also help doctors to detect specific deafness and give some indication of the prognosis for cochlear implantation.
3. Otoacoustic emission (OAE): It mainly understands the functional status of the inner ear. Those who are suitable for cochlear implantation should have inner ear pathology; therefore, DPOAE or TEOAE cannot be elicited bilaterally for conventional cochlear implantation.
4. Multi-frequency steady-state evoked potentials (ASSR): helps to understand the residual hearing of implant candidates, and generally tests the response threshold in the 0.5kHz, 1kHz, 2kHz, and 4kHz speech frequency ranges.
Assessment of hearing ability in children
This is a suprathreshold functional test for pediatric patients with hearing aids to find out how their hearing ability is in the preoperative intervention state. It includes.
1.Lin’s six tones perception test: Lin’s six tones basically cover the normal speech frequency range. Through this test, we can roughly know the speech frequency loss of the child after the hearing aid, and provide basic information for the doctor to judge whether the implantation surgery is needed.
2. Auditory behavior grading questionnaire (CAP): CAP is a grading standard for assessing auditory perception, which is suitable for children of any age, especially for children between 0 and 6 years old, and reflects the child’s level of hearing in the daily environment. If the hearing aid is not effective, implantation surgery can be considered.
3. Auditory Integration Questionnaire (MAIS, IT-MAIS): It is used to assess the spontaneous response of the deaf child to sounds in daily life. The questionnaire covers three main aspects of hearing: acceptance of hearing devices, perception of sounds, and understanding of the meaning of sounds. A score of <20 on the Auditory Integration Questionnaire indicates that the original intervention was ineffective and that cochlear implantation may be considered.
Auditory-verbal ability test
1.Speech recognition rate test (sometimes phrase recognition rate test may be added): Test the ability of deaf patients to acquire, recognize and understand speech information.
2.Speech Intelligibility Test: To understand the deaf patient’s own speech development and spoken language intelligibility.
3. For children or younger deaf patients, the conventional speech test methods may be too difficult for them, so there are also special auditory-speech test methods for children.
①Rhyme recognition, vowel recognition, and bisyllabic word recognition: an average score of ≤ 70% in the three is an auxiliary criterion for determining the need for cochlear implantation.
② Speech Intelligibility Rating Assessment Questionnaire (SIR): a questionnaire was used to assess speech intelligibility.
Second, after the audiological examination meets the criteria for cochlear implantation, deaf patients also require imaging evaluation, including high-resolution temporal bone CT and auditory nerve MRI. CT shows whether the bilateral cochlea and internal auditory canal structures are normal. MRI of the auditory nerve can show fluid filling of the cochlea and internal auditory canal and abnormalities in the development of the auditory nerve. If necessary, a cranial MRI is added to understand any organic/progressive lesions in the brain.
Again, some psychiatric, intellectual, and behavioral assessment is needed to understand the mental development of the child and the presence of psychological disorders and behavioral abnormalities.
All of these examinations or tests are currently the main components of the preoperative evaluation required for cochlear implant candidates. Of course, as experience with cochlear implantation continues to accumulate and medical technology advances, the relevant examinations may change somewhat depending on the actual clinical situation. Some special tests may also be added for those who are ready for implantation with special circumstances. Finally, the interpretation and comprehensive evaluation of the results of all tests is the key to determining whether a deaf patient can ultimately undergo cochlear implant intervention.