1. What is a cochlear implant and who is suitable for a cochlear implant?
To understand cochlear implants, we must first understand how people hear sound. The process of human hearing is as follows: external sound is transmitted to the cochlea through the external ear canal and middle ear, and the cochlea converts the sound into an electrical signal and transmits it to the brain via the auditory nerve, at which point we can feel all kinds of sounds. However, if the cochlea loses its function of converting sound into electrical signals due to stunting or old age, then we will not be able to hear sound. A cochlear implant is a device that replaces the body’s own cochlea to convert sound into electrical signals, and a cochlear implant is a procedure that is performed to implant a cochlear implant into the human body.
So who is suitable for cochlear implantation: ① severe – very severe sensorineural deafness (indicating that life is seriously affected); ② no serious deformity of the cochlea (to ensure that the electrodes can be implanted), and ③ good auditory nerve function and good intellectual development (to ensure that the electrodes can hear after implantation).
2. What is minimally invasive cochlear implantation?
Cochlear implantation is no exception. There are many complications associated with this procedure, such as postoperative hematoma, incision infection, and exposure of the implant or electrodes after several years. This is where minimally invasive cochlear implantation comes in.
The specific approaches are as follows.
① A new type of small 2.5-3 cm incision is used instead of the traditional large 4-6 cm incision.
The advantages are small incisions, less bleeding, less trauma, rapid healing, less chance of infection and hematoma, and near scarless incisions. Small incisions are especially important for children and female patients because children have low resistance and poor tolerance to trauma, while women often have a high demand for appearance.
②The technique of misplacing the skin and subcutaneous incisions is used.
The skin incision and subcutaneous incision are both traumatic to the human body. Although the incision can heal after surgery, it is not as strong and tough as before the incision, so if the skin and subcutaneous incisions overlap each other, the risk of wound dehiscence and implant exposure will be greatly increased. The yellow dotted line in the figure represents the subcutaneous incision, which does not overlap with the skin incision, effectively avoiding incision-related complications.
(iii) Small surgical cavity technique is used.
Currently, we use small papillary contouring instead of standard papillary contouring to reduce the operative cavity and carve grooves in the saved bone wall to accommodate and fix the electrode, thus effectively reducing the risk of electrode dislodgement years later. (implant exposure, electrode exposure have been reported for about 7-10 years)
④ The use of a round window membrane (Austrian cochlea) or round window membrane anterior inferior cochlear opening (Australian electrode) approach for electrode insertion instead of the traditional method of tympanic capsule perforation.
The disadvantage of the traditional cochlear implantation method is that it does not guarantee the opening of the tympanic level (the most suitable location for placing electrodes), and the opening may be located in the vestibular level or between the tympanic level and the vestibular level, thus reducing the stimulation efficiency of the electrodes; moreover, the tympanic level perforation is not parallel to the natural canal of the cochlea, which means that the electrodes are more likely to bend during implantation. Now, we adopt different approaches according to the characteristics of different cochleae: the round window membrane is the end of the tympanic step, so the electrode can be inserted into the tympanic step by making a hole through the round window membrane or below the front of the round window membrane; moreover, the hole from the round window membrane or below the front of the round window membrane is almost parallel to the natural canal of the cochlea, so the electrode can be inserted more smoothly and the chance of electrode bending is naturally low; after such improvement, the electrode can be placed in With this improvement, the electrodes can be placed in the correct position and without bending. (The yellow dotted circle in the figure is the round window membrane, and the blue dotted circle is the lower perforation in front of the round window)
⑤ The electrode implantation method that implements the “soft surgery” concept.
”Soft surgery” is another concept different from “minimally invasive”, the former focuses on preserving the integrity of the original function, while the latter focuses on minimizing the trauma.
3. What is a cochlear implant that preserves residual hearing?
①What is residual hearing?
The patient’s hearing is basically normal at 125, 250, and 500 Hz (low frequency), but there is a significant hearing loss at 1K, 2K, 4K, and 8K Hz (high frequency), so the patient’s normal hearing at 125, 250, and 500 Hz is residual hearing. Of course, the frequency of the presence of residual hearing is not fixed, it can be low frequency hearing, or medium frequency or high frequency.
Why is it important to preserve residual hearing?
First of all, we should know that the cochlear implant only has a limited number of 12-24 electrodes to stimulate all the nerve cells, so it cannot cover every frequency finely. This is why patients with cochlear implants feel better with speech in the narrower frequency range and less well with music in the wider frequency range. If the patient has some residual hearing that was preserved when the electrodes were implanted, then the patient will be able to experience a wider range of frequencies and more detailed and realistic sounds.
What patients are suitable for “cochlear implants that preserve residual hearing”?
Different parts of the human cochlea are responsible for different frequencies of sound, and nerve endings from the bottom to the top of the cochlea are distributed from high frequency to low frequency in order. Therefore, only patients with residual low-frequency hearing have the possibility of preserving their residual hearing, and we strongly recommend “cochlear implantation with residual hearing preservation” for these patients in order to experience sound more delicately.
How is a “cochlear implant for residual hearing preservation” performed?
Preserving residual hearing is a goal that can only be achieved through a number of techniques, including the aforementioned round window (Austrian cochlea) or anterior inferior round window (Australian cochlea) opening technique, cochlear environmental protection technique, and “soft surgery” electrode implantation techniques (including the Australian AOS-Integrated Core technique and the Austrian Flex soft series electrode implantation) to preserve residual hearing.
⑤ What are the actual results of “cochlear implantation for residual hearing preservation”?
Let’s look at a typical case. The patient, a 22-year-old female, was found to have severe hearing loss in the middle and high frequencies and normal hearing in the low frequencies during a preoperative hearing check. We followed all the requirements of the procedure and rechecked the patient’s hearing 3, 6 and 10 days after the surgery. The results of the hearing check showed that the low-frequency residual hearing in the patient’s right ear was almost completely preserved, and the patient felt that the sounds of speech and music were very fine and very good. Therefore, we strongly recommend that patients with good preservation of low-frequency hearing should try to use “cochlear implantation with preservation of residual hearing” if possible to further improve the quality of life.
(6) Can a patient with no residual hearing be treated with a cochlear implant that preserves residual hearing?
The answer is yes, absolutely. Even if the patient does not have residual hearing, the normal physiological function of the cochlea can be preserved to the greatest extent possible with this procedure. This is important for improving the efficiency and longevity of the electrodes and protecting the auditory nerve. Therefore, in our daily cochlear implant work, even if the patient has no residual hearing and the procedure is more difficult than traditional surgery, we still insist on using this procedure in the hope that the patient can retain some normal physiological function and get the maximum benefit from the cochlear implant.