Pure Tone Audiometry/Pediatric Behavioral Audiometry Pure Tone Audiometry is a standardized, subjective behavioral response audiometry test of hearing acuity that includes both air-conduction and bone-conduction hearing thresholds, the results of which are reflected on an audiogram. The purpose of pure tone audiometry is to reflect the hearing level of the smallest sound at each frequency that the subject can hear in a quiet environment, to understand the degree and nature of hearing loss, and to serve as a basis for diagnosis and management. For younger children, who may not be able to cooperate with pure tone audiometry, pediatric behavioral audiometry is required, using a playful approach that is acceptable and cooperative to the child. The results and meaning of the test are the same as for pure tone audiometry. The audiogram is generally represented as a box plot, with the horizontal axis indicating the frequency of the sound (i.e., the pitch of the sound in Hz), from left to right, and the pitch from low to high. The vertical axis indicates the intensity of the sound (i.e., the magnitude of the sound in curves), from top to bottom, with the sound ranging from small to large. “O” indicates the air-conduction hearing threshold of the right ear, and “X” indicates the air-conduction hearing threshold of the left ear. “>” indicates the bone conduction hearing threshold in the left ear, and “<" indicates the bone conduction hearing threshold in the right ear. Under normal conditions, the bone and air conduction thresholds should be the same and both within 25dB. If the bone conduction is within the normal range and the air conduction is outside the normal range, this is conductive deafness, which indicates that there is a lesion in the outer and middle ear, which prevents the conduction of sound to the inner ear. If the bone and air conduction are consistent and both are outside of the normal range, this is sensorineural deafness, which indicates a lesion in the cochlea that senses sound or in the auditory nerve or sub-central structures that transmit sound signals to the center. If both bone and air conduction are outside of the normal range and the two are separated, this is mixed deafness, indicating the presence of both of these conditions. On the audiogram, if the patient's bone conduction hearing threshold is above 70 dB, the deafness is severe or higher and a cochlear implant needs to be considered. Auditory Brainstem Evoked Potential (ABR) ABR is a well-established electrophysiological test. It sends an acoustic signal to the patient through an earphone and, using a probe fixed to the skull, collects signals from the neural response. As an objective test, it does not require the cooperation of the subject and can be performed under pharmacological hypnosis. Therefore, it is widely used in the examination of uncooperative infants and children, and it can reflect the subject's hearing loss with basic accuracy and is one of the diagnostic bases for physicians.ABR examination has its limitations. The frequency characteristics are poor. It generally only reflects the hearing in the high frequency band of 2K-4K. ASSR: multi-frequency steady-state evoked potential Method and principle are similar to ABR mainly sensitive to detect hearing condition in low, middle and high frequencies. 40Hz correlation potential test The method and principle are similar to ABR and is mainly sensitive to detect low frequency hearing conditions. EOAES: Evoked otoacoustic emissions The human cochlea, while receiving sound, emits sound itself. This sound is released into the external ear canal by conduction through the auditory chain and the tympanic membrane and is released in the form of air vibrations. We can detect this sound emitted by the cochlea by placing a microphone-receiver probe in the closed ear canal. Otoacoustic emission is also an objective method of examination. It follows that otoacoustic emission detects the function of the hair cells. These are the audiological tests that must be done before cochlear implant surgery. Based on the results of these tests, the doctor will analyze the patient's deafness site and degree and determine whether the patient's condition is an indication for cochlear implantation. If: abnormal ABR, ASSR, 40Hz correlation potential check + abnormal otoacoustic emissions: the lesion is in the cochlea and is suitable for cochlear implantation. If: abnormal ABR, ASSR, 40Hz correlation potential + normal otoacoustic emissions: the lesion is in the posterior cochlea and cochlear implantation is not recommended. Imaging examinations In addition to the audiological examinations mentioned above, the following two imaging examinations are required before cochlear implantation: 1. CT of the temporal bone: to check whether there are deformed ear structures in the ear that may affect the surgery. 2. MRI of the internal auditory canal: to check for malformations of the auditory nerve to see if there are any central lesions. If: the patient's temporal bone CT and MRI of the internal auditory canal are normal, the cochlear implant can be performed.