What is a cochlear implant?
A cochlear implant is a small electronic device surgically implanted in the inner ear to provide a sense of sound to individuals with severe to profound hearing loss. Unlike hearing aids, which amplify sound for individuals with residual hearing, cochlear implants bypass the damaged portion of the ear and directly stimulate the auditory nerve, allowing the individual to perceive sound (1).
The history of cochlear implantation
The first CI was implanted by William House and John Doyle of Los Angeles, California, in 1961 (2). In 1978, the Australian Graeme Clark implanted the first modern multichannel cochlear implant in an adult patient (3).
Since then, cochlear implants have undergone significant technological advancements and have become a widely accepted treatment for severe to profound hearing loss.
Cochlear implants have been seen as a groundbreaking technology that has transformed the lives of many people who are deaf or hard of hearing. These devices can give individuals a sense of sound and help them communicate effectively in the hearing world. While cochlear implants have sparked debates within the Deaf community about identity and cultural belonging, they are generally viewed as a positive and life-changing intervention for many individuals.
Components of a cochlear implant
The components of a cochlear implant system include an external sound processor, a transmitter coil, and an internal receiver-stimulator. The external sound processor captures sound from the environment via a microphone, processes it, and sends it via radio to the transmitter coil, which is attached to the skin behind the ear. The transmitter coil then transmits the processed sound signals to the internal receiver-stimulator, surgically placed under the skin behind the ear. The receiver-stimulator converts the signals into electrical impulses and sends them to the electrodes implanted in the cochlea, bypassing the damaged hair cells and stimulating the auditory nerve.
Modern technology includes a loose, separate, externally worn processor where a microphone, speech processor and transmitter are all housed in a single unit placed behind and away from the ear.
How long does a cochlear implant last?
Cochlear implants are designed to be permanent solutions for individuals with severe to profound hearing loss. The internal part of a cochlear implant, surgically implanted in the inner ear, is expected to last a lifetime. However, the external components, such as the sound processor, may need to be replaced or upgraded every few years to keep up with technological advancements. Regular maintenance and check-ups with an audiologist are essential to ensure the longevity and effectiveness of a cochlear implant (4).
Cochlear implant candidates
Criteria for performing cochlear implants include individuals with severe to profound sensorineural hearing loss who do not benefit from hearing aids. It is important to note that cochlear implants are not indicated for all types of hearing loss, such as conductive or mixed hearing loss or if there is damage to the auditory nerve.
The reasons for performing Cochlear implants are to restore or improve the ability to hear and understand speech, improve quality of life, and enhance communication with others.
Children are recommended to be implanted as early as possible to allow for optimal speech and language development, as there is a critical period for auditory development. The ultimate goal of a cochlear implant is for the patient to achieve spoken language communication.
Can residual hearing be preserved with cochlear implanation?
Electro-acoustic stimulation (EAS) is a technology used in cochlear implants to preserve residual hearing and improve speech understanding in individuals with severe to profound hearing loss. EAS combines electrical stimulation of the cochlea with acoustic amplification to provide a fuller and more natural sound experience.
The cochlear implant system consists of two components: an internal implant surgically placed in the cochlea and an external speech processor that captures and processes sound. In EAS, the speech processor is designed to amplify and deliver low-frequency sounds to the cochlea through a hearing aid or a specialized electrode array. In contrast, high-frequency sounds are delivered through electrical stimulation.
By preserving residual hearing and combining electrical and acoustic stimulation, EAS helps individuals with cochlear implants to understand speech in noisy environments better and appreciate music. This technology can also improve the overall quality of sound perception and assist users in localizing sounds.
Cochlear implantation in single sided deafness
Single-sided deafness (SSD) is when an individual has normal hearing in one ear but severe to profound hearing loss in the other. This can significantly impact a person’s ability to localize sounds, understand speech in noisy environments, and engage in conversations with multiple people.
Cochlear implants are a potential treatment option for individuals with single-sided deafness. While cochlear implants are typically used for severe to profound hearing loss in both ears, they can also be beneficial for individuals with SSD, as they can provide access to sound in the deaf ear and improve overall auditory function.
Studies have shown that cochlear implants in individuals with single-sided deafness can help improve speech understanding in noisy environments, localize sounds more accurately, and enhance overall quality of life. However, individuals with SSD need to undergo a thorough evaluation by an audiologist and otologist to determine if they are a suitable candidate for a cochlear implant.
Cochlear implants can be a viable treatment option for individuals with single-sided deafness, providing them with improved hearing and communication abilities.
How early can a cochlear implant be performed?
Research has shown that the earlier a child receives a cochlear implant, the better their speech and language development outcome. Ideally, a cochlear implant should be performed before age one, as this maximizes the child’s ability to develop language and communication skills at the same pace as their peers.
Early intervention is crucial in children with hearing loss, as the brain is most receptive to learning language in the first few years of life. Providing a child with a cochlear implant before the age of one allows them to develop their auditory skills and speech patterns in a way that closely mirrors that of their hearing peers.
The outcomes of cochlear implantation in young children are excellent, with many children reaching age-appropriate language milestones and achieving success in school and social settings. Therefore, parents and healthcare providers must act quickly in identifying and treating hearing loss in children to give them the best possible chance at a successful future.
The process of evaluation
It is vital to have a multidisciplinary team involved in cochlear implantation to ensure the best possible outcomes for the patient. This team typically includes an otologist or ENT surgeon, audiologist, speech-language pathologist, and hearing implant specialist. Each member of the team plays a crucial role in evaluating the patient’s candidacy for a cochlear implant, performing the surgery, programming the implant, and providing ongoing support and rehabilitation. Collaboration among team members ensures that the patient receives comprehensive care and support.
Special tests before cochlear implantation
Before a cochlear implant surgery, a detailed medical examination, radiological studies with MRI and CT scans, and a comprehensive audiology assessment are conducted to ensure the individual is a suitable candidate for the procedure. Other tests may also be necessary.
Otoplan
One new tool that can assist the surgeon before, during, and after surgery is a software called OTOPLAN®. It was made by CASCINATION AG from Switzerland and MED-EL from Austria. This software allows the doctor to see the cochlear anatomy in 3D before surgery, choose the right electrode for the patient, and check the position of the cochlear implant after surgery.
Choosing the right cochlear implant
According to Dr Hofmeyr, only two cochlear implant systems on the market are known for their reliability and effectiveness. Patients are advised to inquire about the reliability of an implant system and whether it is MRI compatible up to 3 Tesla.
It is crucial to recognize the ongoing research involved in developing implants. Understanding the level of investment a company puts into research and development can provide insight into the quality and efficacy of its products. Considering this aspect can ensure the selection of a reliable and innovative implant.
It is essential for individuals considering a cochlear implant to weigh the potential costs against the benefits. While the initial cost of the surgery and device may be high, the long-term benefits of improved hearing, speech, and overall well-being usually outweigh the upfront expense.
Cochlear implant surgery
During the surgery, an electrode array is inserted into the cochlea, which is the part of the inner ear responsible for hearing. This array stimulates the auditory nerve directly, bypassing damaged or non-functioning hair cells. The surgery is performed under general anaesthesia and typically takes about two hours. After implementation, the integrity of the device is confirmed in the theatre, and a preliminary estimate of the mapping program is established.
What happens after the surgery?
After undergoing surgery for a cochlear implant, the device is not immediately activated or switched on. Instead, a healing period of approximately six weeks allows the surgical site to heal properly. Once this healing period is complete, a trained audiologist can activate the cochlear implant.
Activation of the cochlear implant is a crucial step in the process, as it marks the beginning of the user’s journey towards hearing with the device. However, it is essential to note that the initial activation is just the first step in the process. The cochlear implant must be fine-tuned and adjusted over time to ensure optimal performance.
Regular follow-up appointments with the audiologist are essential during the first year after activation. These appointments allow the audiologist to make any necessary adjustments to the cochlear implant settings based on the user’s feedback and experiences. This fine-tuning process maximizes the user’s ability to hear and understand speech effectively
Dr Hofmeyr's experience in cochlear implants
Dr. Hofmeyr has extensive experience in cochlear implantation, having implanted over 400 patients with all three available devices in South Africa. As the director of Cape Hearing Implants, he is a respected expert in the field. Additionally, he is a member of the South African Cochlear Implant Group (SACIG), further showcasing his expertise and dedication to improving hearing health.