Cochlear Implants

Overview

Cochlear implants are electronic devices designed to assist individuals with hearing loss. While they can enhance the hearing of various sounds and facilitate understanding of conversations, they cannot fully restore hearing.

These implants operate by establishing an alternative pathway for sound transmission, bypassing the damaged parts of the ear. Cochlear implants function by establishing a new route within your ear. This pathway channels sound from the outer ear to the inner ear, where it initiates an electrical signal. This signal is then conveyed by your auditory nerve to your brain, where it is interpreted as speech, music, or other sounds.

Types of cochlear implants

The types of cochlear implants vary according to where the external sound processor is located. Among the devices utilized in cochlear implants are external sound processors. The processor could be attached behind your ear, your scalp, or your clothes.

To understand how cochlear implants function, it’s useful to know how the hearing process works. Hearing begins when sound travels from your outer ear through the middle ear to the inner ear, which houses the cochlea, a critical component for hearing.

Within the cochlea are tiny hair cells that connect to the auditory nerve. When sound travels from the outer ear to the inner ear, it reaches the cochlea, generating an electrical signal. This signal is carried by the auditory nerve to the temporal lobe of the brain, where it is perceived as sound and interpreted as speech, music, or other noises.

Cochlear implants bypass the inner ear structure, creating an alternative route for sounds to reach the brain. Here’s how they work:

• To filter noises entering your outer ear, you use a sound processor.
• The transmitter, which is magnetized and fastened to your head, receives signals from the sound processor.
• The signals are transformed by the transmitter into electric impulses and sent to electrodes inside your cochlea.
• The impulses are collected by the electrodes in your cochlea and then transmitted to the hearing nerves.
• Your brain receives information about sound input from the hearing nerves.

Reasons for using the device

Studies suggest that many people could benefit from cochlear implants, yet only 2% of potential candidates have them. It’s worth mentioning that you don’t need total hearing loss to benefit from cochlear implants. The U.S. Food and Drug Administration (FDA) has granted approval for cochlear implants to individuals experiencing moderate, profound, or severe hearing impairments. This encompasses those with hearing loss in both ears, as well as those with single-sided hearing loss or with normal hearing for low pitches that drops off to moderate to severe hearing loss. Cochlear implants are also deemed suitable for children aged 9 months and above.

If you use hearing aids but still find it difficult to understand speech, you might be a good candidate for cochlear implants, even if the aids offer some help.

Typically, doctors recommend cochlear implants if you meet the following criteria:

• Experience a noticeable loss of hearing in one or both ears.
• Have hearing aids but wish their quality was higher.
• Do not suffer from any health conditions that increase the risk of operation.

Risks

There are complications involved with any surgery, particularly those related to general anesthesia and infection. The advantages of cochlear implants much exceed the risks associated with surgery. The following are risks unique to cochlear implant surgery:

• Loss of residual hearing: Residual hearing refers to the remaining ability to hear despite experiencing severe or profound hearing loss. However, cochlear implant surgery has the potential to damage any remaining cochlear hair cells, thereby eliminating this residual hearing.
• Tinnitus: Tinnitus nor ringing in the ear is usually lessened by cochlear implants, however it can become more apparent during surgery.
• Dizziness or vertigo: Your cochlea aids with balance management as well. Your sense of balance may be affected by surgery.
• Nerve damage: In rare cases, cochlear implant surgery can damage nerves that pass through the middle ear and near the implant site. If this occurs, it might result in taste issues, facial weakness on the side with the implant, or numbness around the ear.
• Meningitis: In rare instances, individuals with atypical inner ear structures may develop meningitis. To mitigate this risk, doctors often recommend vaccination against meningitis.
• Cerebrospinal fluid leaks: Occasionally, individuals with cochleae of irregular shapes may encounter this problem. This involves the presence of fluid within the tissue surrounding the brain and spinal cord, including the subarachnoid space, which connects to a portion of the inner ear. During cochlear implant surgery, holes are made in the inner ear. In some cases, this can lead to a leak of cerebrospinal fluid.

Before the procedure

This is what your hearing team could do:

• Hearing tests: An audiologist might conduct various tests to assess the extent of your hearing loss, evaluating your ability to hear sounds and understand speech with and without hearing aids. These tests may include an Auditory Brainstem Response (ABR) test, which examines the connections between your inner ear and brain. Audiologists often use the ABR test to assess hearing in children and individuals who are unable to complete pure-tone audiometry tests.
• Vestibular test battery: Your inner ear controls balance. An additional method to assess inner ear health is through vestibular testing.
• Imaging tests: To assess the anatomy of your inner ear, doctors may do a Computed Tomography (CT) scan or Magnetic Resonance Imaging (MRI).

During the procedure

Prior to surgery, you will be given general anesthetic. Next, your surgeon:

• Cuts a little opening behind your ear to place the implant.
• Creates an opening in the bone behind your ear, which connects to your cochlea.
• Makes use of the opening to position the electrodes on the implant’s end that link the cochlea and transmitter.
• Closes the wound behind your ear with sutures.

After the procedure

During your follow-up session, which is scheduled for around two weeks following your surgery, your audiologist will:

• Install the sound processor and make sure it fits properly.
• Verify that the electrodes and transmitter are operational.
• Activate the device and evaluate your auditory perception.
• Fine-tune the settings of the device until you achieve optimal auditory clarity.

Hearing with a cochlear implant involves a learning process. When you experience hearing loss, your brain needs to adapt to processing sounds differently. Many cochlear implant users collaborate with audiologists or Speech-Language Pathologists (SLPs) to help their brains interpret sounds effectively. To optimize the advantages, patients need to be committed to engaging in auditory-based relearning.

Outcome

Significant improvement after receiving a cochlear implant may take time as your brain adjusts to receiving signals from your hearing nerve. Typically, patients notice enhanced hearing about a month after their implant is activated, although it can take three to six months for some to fully adapt. Faster progress is often seen in individuals who regularly engage in hearing exercises and therapy, wear their implants consistently while awake, and adhere to recommended wearing schedules. Initially, sounds may seem different from what you remember, possibly sounding mechanical or artificial, as the sensations from the implant differ from natural hearing.