Cochlear Implants: Restoring Hearing, Transforming Lives

Our ears detect sound waves from all around us and convert them into nerve signals that our brain can understand as sound. The ear has three parts: the outer ear, the middle ear, and the inner ear.

1. Sound waves enter through the outer ear and travel through the ear canal, where they vibrate the eardrum.
2. The eardrum then vibrates the ossicles, which are very small bones in the middle ear that connect the outer and inner ear.
3. The ossicles then carry these sound vibrations into the fluid-filled cochlea.
4. Specialised hair cells in the cochlea move with the vibrations and stimulate the auditory nerve with tiny electrical pulses.
5. These electrical nerve signals travel along the auditory nerve to the brain, where they are perceived as sound.

A cochlear implant replicates the sense of hearing by electrically stimulating the cochlea to bypass the non-functioning hair cells of the inner ear.

1. The audio processor detects the sounds and transmit them to the implant as electrical signals.
2. The implant converts these signals into electrical pulses that are sent into the electrical array in the cochlea.
3. In the cochlea, these electrical pulses bypass the non-functioning hair cells by directly stimulating the nerve fibres connecting to the hair cells.
4. The nerve fibres sent signals along the auditory nerve to the brain, where the signals are perceived as sound.

Children may benefit from cochlear implant if they:

• Have severe to profound sensorineural hearing loss in both ears.
• Have gained limited or no benefit from hearing aids and continue to have speech and language delay.
• Have slow and no response to speech sounds despite hearing aid use.
  

Patient undergoing auditory training session with speech therapist.

Benefits:

• Improved access to sound that is crucial for speech and language development.
• Children with early implantation have better auditory performance, speech production and receptive language compared to their peers who receive cochlear implant later.¹
• Better educational outcomes and quality of life compared to children without cochlear implant, with similar level of hearing loss.²

Limitations:

• The cochlear implant needs to be paired with aural rehabilitation for optimal outcomes.
• Depending on the age of implant, commitment to aural rehabilitation and coexisting medical conditions, the outcome may vary.
  

Cochlear implant user wearing a cochlear implant audio processor

There are 3 categories of adults who may benefit from cochlear implant.

Adults with severe to profound sensorineural hearing loss in both ears and continue to experience difficulty hearing despite using hearing aids (hearing aid amplification is no longer sufficient).

• Benefits:
  • Improved speech understanding and communication abilities.³
  • Increased ability to hear in noisy places.
  • Improved quality of life and general well-being.³
  • Improved cognitive function.⁴
• Limitations:
  • The cochlear implant needs to be paired with aural rehabilitation for optimal outcomes.
  • Depending on the duration of deafness, age of implantation and cognitive function, the outcome of cochlear implant may vary.
  • Possible need for extended rehabilitation to achieve optimal results, especially in patients with prolonged hearing loss that is not rehabilitated with hearing aids.

Adults with profound hearing loss in one ear and normal or near normal hearing in the other ear.

• Benefits:
  • Improved sound localisation⁵
  • Enhanced understanding of speech, especially in noisy environments⁵
• Limitations:
  • Variability in outcomes depending on the duration of deafness.
  • Rehabilitation needs and adjustment period can vary significantly from person to person. 
  • Some patients may experience less improvement in spatial hearing compared to those with implants in both ears.

Adults with severe to profound sensorineural hearing loss who also suffer from severe tinnitus (ringing in the ear) that negatively impacts on their sleep quality, daily activities, and mental health.

• Benefits:
  • Reduction or elimination of tinnitus symptoms such as sleep problem,
    restless, anxiety and depression.
  • Improved quality of life and reduced psychological distress associated with chronic tinnitus.^6-8
• Limitations:
  • Not all patients may experience a significant reduction in tinnitus.
  • Variability in outcomes based on individual patient factors and duration of tinnitus.
  • The need for continued follow-up and possible adjustments to the implant settings.
  • In some rare cases, some patients may experience more tinnitus after the surgery.
    

The cochlear implant journey is a long-term partnership between the patients, their family members and a multi-disciplinary team which consists of the implant surgeon, the audiologist, and the speech therapist.

Before embarking on this journey, the team would discuss with patients about their daily hearing needs, hearing aid usage, medical conditions, and expectations with regards to the surgery and implant usage.

Our multi-disciplinary team would first assess the patient for suitability for cochlear implant surgery and prepare him/her on what to expect during and after the surgery.

Cochlear Implant Journey Map

• Pre-Surgery:
  • Comprehensive hearing, speech and balance examination and other medical examinations.
  • Discussion on suitability of cochlear implant based on hearing profile, contraindication of surgery and motivation for the surgery and rehabilitation.
  • Discussion of expectations and potential risks.
  • MRI or CT scans of the ears and the head.
  • Ensure adequate vaccination for pneumococcal disease as having a cochlear implant increases the risk for meningitis. 
  • Discussion and selection of cochlear implant types and brands.
  • Financial counselling.
  • Introduction to the rehabilitation process after cochlear implant surgery.
• During Surgery:
  • The procedure typically lasts 2-4 hours and is performed under general anaesthesia.
  • Placement of the implant involves making a small incision behind the ear and inserting the electrode array into the cochlear.
  • The implant is usually tested after inserting to make sure it is working well, and an X-ray is done after surgery. 
  • There will be a head bandage applied immediately after surgery to be left on overnight.
  • Most patients can go home the next day after surgery.
• Post-Surgery:
  • Patients may experience discomfort and will need to follow specific post-operative care instructions.
  • Initial activation of the cochlear implant occurs 2-4 weeks after surgery.

Post-surgery Aural Rehabilitation Session with a Speech Therapist

The rehabilitation process for a cochlear implant involves several stages, which aim to help patients adapt to the new sounds they are hearing and maximize the benefits of the implant. The duration and intensity of rehabilitation can vary depending on factors such as the patient's age, duration of hearing loss before implantation, and individual progress.

• Switch-on of cochlear implant
  • 2-4 weeks after surgery, the audiologist will switch on the cochlear implant by connecting it with an audio processor.
  • The audiologist will show the patient on how to use the audio processor and its care and maintenance.
• Follow-up with the audiologist for mapping and programming
  • Several follow-up visits are required to fine-tune the implant. This process is known as mapping.
  • The audiologist will test different frequencies and volumes to tailor the implant to the patient’s preference and needs.
• Weekly auditory rehabilitation with the speech therapist
  • This is the most critical part of the process and involves training the brain to interpret the new sound signals.
  • Some training sessions include sound detection, auditory training, listening practice and speech therapy.
  • The speech therapist will also provide guidance or tips on communication skills and repair strategies.
  • Patient is required to attend weekly auditory rehabilitation for 3- 6 months for optimal outcomes. Depending on their progress and needs, some patients may require longer and more frequent follow-ups.
• Regular follow-ups
  • Regular visits to the audiologist and the speech therapist are necessary to monitor progress and to make any necessary adjustments to the implant settings.
• Support and counselling
  • Ongoing support from professionals, support groups, and family are crucial for adapting to the implant and addressing any emotional or psychological challenges.
    

Cochlear implant surgeries are generally safe and can greatly improve the quality of life for individuals with severe hearing loss. However, as with any surgical procedure, there are risks and potential complications, including:

• Surgical Risks: Infection, bleeding, and adverse reactions to anaesthesia.
• Device-Related Issues: Device malfunction or failure, which may require additional surgery to repair or replace the implant.
• Hearing Loss: Residual hearing can be lost in the implanted ear.
• Balance Issues: Temporary or permanent dizziness, or issues with sense of balance.
• Facial Nerve Damage: Potential risk of facial nerve injury, which can cause facial paralysis.
• Tinnitus: Worsening of tinnitus (ringing in the ears).
• Meningitis: Increased risk of meningitis, though this is rare.

Based on the guidance recommendation by the Ministry of Health’s Medical Technology Advisory Committee:

• All Singaporean Citizens and Permanent Residents who have bilateral severe to profound hearing loss will be eligible for government subsidy for their first cochlear implant in restructured hospitals.
• Funding for bilateral cochlear implant is only for children below 6 years old unless there are special considerations (e.g., large vestibular aqueduct syndrome (LVAS), meningitis, irradiated ears).
• The amount of government subsidy depends on the ward class selected, and family household income.
• Subsidies apply only to the standard packages or replacement packages of cochlear implant devices listed in the MOH’s Agency for Care Effectiveness (ACE) website.
• Subsidies will not apply to devices and accessories that are not included in the standard or replacement packages of cochlear implant devices, including replacement of, or upgrades to, internal implants.