Cochlear Implants | How Do They Work? | MedStar Health

Cochlear implants are small, implantable devices that restore hearing perception to those who do not benefit from wearing conventional hearing aids. While the conventional hearing aids amplify sounds, the cochlear implant bypasses impaired inner ear structures and stimulates the hearing/auditory nerve. As of December 2012, approximately 324,000 people worldwide have received cochlear implants. The Georgetown Cochlear Implant Program offers some of the most advanced options in auditory rehabilitation including bilateral cochlear implants, hybrid, and other hearing preservation devices and approaches.

How natural hearing works

Understanding how natural hearing works is important before explaining how a cochlear implant works.

image of a Cochlear Implant
  1. Sound waves enter the ear canal and contact the ear drum (tympanic membrane).
  2. After the ear drum picks up the sound, it transmits sound through the three ear bones, known as the hammer (malleus), anvil (incus), and stirrup (stapes). The stirrup passes the vibrations to the inner ear fluids within the cochlea.
  3. Fluid waves travel through two and a half (2 ½) turns of the cochlea and stimulate the cochlear sensory organ, hair cells.
  4. The hair cells are tuned to respond to the wide range of frequencies or pitches of the original sound waves, initiating signals within their corresponding hearing/auditory nerve endings prior to sending them to the brain.

How cochlear implants work

The use of cochlear implants for the treatment of moderate to profound hearing loss is a revolutionary treatment and has been called one of the single most effective health interventions of our time. A cochlear implant is an electronic device that is partially implanted surgically into the cochlea, the hearing organ of the inner ear. It uses electrical current to bypass damaged or missing portions of the inner ear and stimulates remaining hearing nerve fibers. A microphone, processor, and transmitter are worn externally to control the implanted internal device.

Image showing a cochlear implant and how it work

Implants vs. hearing aids

Hearing is a complex process that originates in the cochlea: the organ of hearing that is located inside the temporal bone of the skull. The cochlea contains thousands of microscopic sensory cells that work much like the keys on a piano. Each sensory cell, called a hair cell, is organized and tuned to match a specific pitch. In a normal hearing person, these sensory cells respond to acoustic/sound information in the environment and translate it into a neurological code that is transmitted through the hearing nerve to the brain where understanding of the sound happens. If any of these sensory cells do not work properly, the information that arrives in the brain will be distorted and incomplete. The listener may have difficulty understanding what is said.

In the presence of hearing loss, when the sensory hair cells are permanently damaged and/or missing, incomplete, and distorted sound arrives at the brain. Hearing aids only make sounds louder and can compensate for partially damaged hair cells, but they cannot overcome significant and permanent hair cell damage.

A cochlear implant is not a hearing aid. Instead, it is a neural prosthesis that helps to provide hearing to people with moderate to profound hearing loss by bypassing the damaged sensory cells of the cochlea for individuals that obtain little or no benefit form sound amplification by hearing aids. The patient’s traditional means of hearing “acoustic hearing” is then replaced with “electric hearing” through the cochlear implant.

Criteria (who is a candidate)

With technical advances in cochlear implant technology, the minimal criteria have been evolving, the following is the current criteria for adult and child cochlear implant candidates:

Adult criteria

  1. Moderate to profound sensorineural hearing loss (refers to damage to the inner ear or nerve pathways form the inner ear to the brain)
  2. Little or no benefit from hearing aids
  3. No medical contraindications
  4. Clear understanding of cochlear implantation and end results
  5. A commitment to the process and follow-up appointments

Pediatric criteria

The Food and Drug Administration (FDA) has approved the use of cochlear implants for children who meet the specified criteria:

  1. Children at least 12 months of age
  2. Children with severe-to-profound hearing loss
  3. Children who are healthy enough to have the surgery
  4. Children whose families are motivated to follow through with auditory verbal rehabilitation therapy and full-time device use
  5. Younger children:

    1. No benefit from well-fitted hearing aids that are worn all of the time, and
    2. No progress or change in speech and language development
  6. Older children:

    1. Unable to understand at least 30% of the words with listening only tests


Patient expectations can be a sensitive and critical issue to address both pre-operatively and post-operatively with not only the patient undergoing the surgery but with the patient's family and friends. Post-operative outcomes for cochlear implant recipients can take many recognizable forms, including sound awareness (known as detection) at the most basic level to open-set speech recognition (referring to the patient’s ability to identify what is said without prior knowledge of what the word or sentence choices are) in noise.

The amount of benefit that a patient perceives is largely dependent on his/her past hearing history and exposure to amplification and spoken language. Patients who developed spoken language prior to the onset of significant hearing loss are routinely identified as post-lingually deafened. A patient with this hearing background is different from a patient whose primary means of communication is through sign language or other forms of manual and visual communication. Patients who rely on sign language are often described as being pre-lingually deafened, meaning that the hearing loss preceded their development of spoken language. Post-lingually deafened adult patients tend to have better outcomes than pre-lingually deafened adult patients after cochlear implantation. In those pre-lingually deafened pediatric patients implanted early in their development (12-24 months), outcomes with cochlear implants may be equivalent to those of post-lingually deafened pediatric patients. After this early period, post-lingually deafened pediatric patients tend to have better outcomes than pre-lingually deafened pediatric patients after cochlear implantation.

Research has shown auditory verbal therapy and speech-language rehabilitation to be viable means for improving speech perception outcomes for most cochlear implant recipients. Referral for these services is optional for each patient and can be discussed with your audiologist and speech-language pathologists we are supportive of this decision. Both post-lingual as a well as pre-lingual patients can be excellent candidates for cochlear implantation, and we review each patient as a unique and separate case. Cochlear implantation is a life-changing experience and we believe in serving all of our patients to the best of our knowledge and expertise.

Implant costs

Cochlear implantation and its benefit to individuals with moderate to profound hearing loss is a well-documented medical procedure. Medicare along with most major, private insurance companies recognize its significant benefit and medical necessity and typically offer 80-100% coverage of the costs of the surgery and the implant system.

Once candidacy for the process has been determined and a surgery date established, the Department of Otolaryngology will work with your insurance on your behalf to obtain an authorization for the cochlear implant surgery. Every patient's medical coverage is unique, which can affect the overall cost of the surgery. The MGUH Department of Otolaryngology-HNS will work with you with regards to financing. We will discuss your individual insurance plan and your potential out-of-pocket expenses associated with the surgery.

Selecting a device

With three cochlear implant companies manufacturing reliable FDA approved devices, flexibility exists among the available technology to make the “best” choice for each and every patient. We work equally with all three cochlear implant devices and are equipped to service and program implant from these companies: Cochlear Corporation, MED-EL Corporation, and Advanced Bionics Corporation.

The ultimate decision-making process includes the collaboration of the patient's desires with the recommendations of the implant team (surgeon, audiologist, family). All three implant manufacturers have a long-standing history of building and creating reliable speech processors that offer strong patient performance.

They are committed to the functioning of the device for the lifetime of the patient. These manufacturers are constantly seeking to improve the existing technology so as to offer new options to patients while ensuring back-compatibility to the internal devices that may have been implanted years earlier.

With most advances, newer, sleeker, and more efficient processing units become available which means that the upgrade process is understood and supported by the companies as well as insurance providers.

A variety of accessories and features come with each of these implants and information on these options will be provided to the patients by the audiology. You will discuss your personal needs with your audiologist to determine the best implant system to meet the demands of your lifestyle.

Regarding patient preference, we encourage patients to obtain literature from all implant manufacturers as well as visit the company websites online to gain more information about device technology, before engaging in the selection process. We are comfortable with all manufacturers and are willing and able to accommodate patient preferences.

Abnormal cochlear or external ear anatomy will be assessed via CT and/or MRI scan. The surgeon may have advice and valuable input about a specific internal receiver, which may work best with the patient’s anatomy. In the end, this could influence the external wearing options for the patient.

Cochlear implant process

  1. Initial audiology testing and counseling: Extensive hearing testing will be performed in a sound booth with and without hearing aids. The information combined with the history of hearing loss is used by the audiologist to assess the potential utility of the cochlear implant. If you are an audiologic candidate, your audiologist will spend time counseling and educating you about cochlear implants. This will help you to understand all that is involved before you decide to proceed with the rest of the process. You will be given information on the available cochlear implant devices from all manufacturers.
  2. Otologic medical evaluation: A full medical history and physical exam along with a review of hearing test results will be performed by a cochlear implant surgeon. If this evaluation is consistent with a cochlear implant being the best option, then the next phase of evaluations will be scheduled.
  3. Imaging studies: An imaging study (either an MRI or CT scan) will be ordered and is required for all patients to evaluate inner ear anatomy and to screen for any brain conditions prior to the placement of the implant.
  4. Second phase audiology hearing tests: You may be required to have additional audiology testing. There are other sentence and word recognition tests performed in quiet and in the presence of background noise that enable us to better compare your hearing abilities after cochlear implantation with those prior. If you have not already, you will be asked which cochlear implant brand you have selected.
  5. Insurance precertification: Obtaining approval from your insurance company for cochlear implantation can take several weeks and will be performed by staff in the MGUH Otolaryngology-HNS department.
  6. General medical preoperative exam by your primary physician: If you are age 40 or older and/or if you have other medical conditions (high blood pressure, heart conditions, diabetes, etc), you may need to see your primary physician for an exam that includes an EKG, chest X-ray, and general blood tests, as indicated, before we can schedule your surgery. Your physician’s office must fax us these results with a note from the physician stating that you are in reasonable condition to undergo the implant surgery. Pneumococcal vaccine, as recommended by the US Food and Drug Administration and Centers for Disease Control and Prevention, can be obtained from your primary care physician (See below).
  7. Scheduling surgery: When all of the above steps are complete, a surgery date will be scheduled. Your physician will review all of the information, confirm which ear is to be implanted, and which device has been selected.
  8. Cochlear implant surgery: The surgery takes approximately 2 to 3 hours to perform. The majority of patients go home the same day of surgery. Further surgical details will be discussed with your physician and can also be found within this section of the web site.
  9. One-week postoperative check: You will return to see your physician 1 week after surgery to check the incision for proper healing.
  10. Activation and programming, start rehabilitation/auditory-verbal therapy: Cochlear implant activation usually takes place 4 weeks after surgery. At that time, the patient will be fitted with the external parts of the device, which requires programming of the external speech processor by the cochlear implant audiologist. During this process, the patient will begin to hear their first sounds generated by the implant. That day you will have the processor programmed and leave the office with the implant functioning. This is the beginning of learning to hear with the implant. If indicated, you will schedule Auditory-Verbal Therapy to begin sometime after this visit.

The programming of the external speech processor is a procedure that must be repeated 1 week later and then periodically thereafter. The reason for this is because the implant system must be programmed to suit each individual's needs. Each patient's tolerance of sound improves with time. Therefore, the implant stimulation level can be adjusted to suit each patient’s needs. The implant team is committed to work with the implant recipient as long as it is necessary to ensure optimal benefit from the device.


Meningitis is a possible, albeit very rare, complication of cochlear implantation. However, when present it can cause serious consequences.

Meningitis is an infection of the lining of the surface of the brain. Early symptoms of meningitis include fever, irritability, lethargy, and loss of appetite in infants and young children. Older children and adult may also manifest headaches, stiff neck, nausea, vomiting, and confusion or alteration in consciousness. Physicians are encouraged to consider a diagnosis of meningitis in cochlear implant patients when such symptoms exist and to begin appropriate treatment as soon as possible.

The unusual occurrence of meningitis can be decreased even further through the use of appropriate vaccination. We recommend vaccinations for patients with cochlear implants. If you have not received a vaccination recommendation sheet, please ask our office staff. If you have any issues regarding this issue, please contact your physician.

Based on CDC recommendations, all persons with cochlear implants should receive age-appropriate pneumococcal vaccination with 7-valent pneumococcal conjugate vaccine (PCV7) (Prevnar®), 23-valent pneumococcal polysaccharide vaccine (PPV23) (Pneumovax®23), or both according to the Advisory Committee on Immunization Practices (ACIP) schedules for person at high risk.

Because the rate for pneumococcal meningitis is higher in children with cochlear implants and Streptococcus pneumoniae is the most common pathogen causing bacterial meningitis in cochlear implant recipients of all ages with meningitis of known etiology, ACIP recommends the following for persons who have or are scheduled to receive a cochlear implant:

  • Children aged <2 years with cochlear implants should receive PCV7, as is universally recommended; children with a lapse in vaccination should be vaccinated according to the catch-up schedule issued after the PCV7 shortage resolved (4.5).
  • Children aged 2 to 5 years with cochlear implants who have not received PCV7 should be vaccinated according to the high-risk schedule; children with a lapse in vaccination should be vaccinated according to the catch-up schedule for persons at high risk issued after the PCV7 shortage resolved (3.4). Children who have completed the PCV7 series should receive PPV23 ≥2 months after vaccination with PCV7 (3).
  • Persons aged 5 to 64 years with cochlear implants should have received PPV23 according to the schedule used for persons with chronic illnesses, a single dose is indicated (6).
  • Persons planning to receive a cochlear implant should be up-to-date on age-appropriate pneumococcal vaccination ≥2 weeks before surgery, if possible.
  • Adults (age 19 years and older) who have NOT had any prior pneumococcal vaccinations need one dose of PCV13 (Prevnar 13) followed 8 weeks later by PPV23. A PPV23 booster is required at age 65. Adults (age 19 years and older) who have had prior vaccination only with PPV23, now also need one dose of PCV13 to be given 12 months after their PPV23 shot.


  1. CDC, Pneumococcal vaccination for cochlear implant recipients. MMWR 2002;51;931.
  2. Reefhuis J, Honein MA, Whitney CG, et al. Risk of bacterial meningitis in children with cochlear implants, USA 1997-2002. N Engl J Med 2003;349:433-43.
  3. U.S. Food and Drug Administration, Public Health web notification: cochlear implant recipients may be at greater risk for meningitis.
  4. CDC. Preventing pneumococcal disease among infants and young children: recommendations for the Advisory Committee on Immunization Practices. MMWR 2000:49(No. RR-9)
  5. CDC. Use of Vaccines to Prevent Meningitis in Persons with Cochlear Implants. Updated June 19, 2015.

Risks specific to cochlear implant surgery

  1. Loss of natural (or residual) hearing in implanted ear
  2. Greater chance for infection around the brain and spinal cord (known as meningitis)
  3. Facial nerve stimulation resulting in involuntary facial twitching
  4. Swelling (inflammation) / Pushing or thrusting out (extrusion) of device
  5. Soreness, redness, breakdown of skin in area around device
  6. Failure of implanted device, sometimes requiring reimplantation

Risks with any ear surgery

  1. Numbness / tenderness around the ear 
  2. Injury to the facial nerve / facial paralysis (facial drooping) 
  3. Taste change (dry mouth or metallic taste in mouth) 
  4. Leak of inner ear fluid (perilymph) or fluid that surrounds the brain (cerebrospinal fluid) 
  5. Dizziness or vertigo 
  6. Ringing in the ears (tinnitus) 
  7. Local complications such as blood/fluid collection or infection at or near surgery site 
  8. Rashes (skin reactions) 

General risks

  1. Post-surgery pain, scarring, bleeding, and infection
  2. Risks associated with being put to sleep or general anesthesia (problems with the heart, lungs, kidneys, liver, and brain due to general anesthesia)


The surgical placement of cochlear implants has been performed for over 40 years. Newer implant designs and surgical techniques allow us to place these devices with very few complications and excellent cosmetic results.


The procedure is performed in a day surgery unit with most patients going home the same day. General anesthesia is administered in the operating room, and a small amount of hair behind the ear is shaved, if necessary. An incision is made in the crease behind the ear, which makes the scar very inconspicuous once it has healed.


A pocket is created under the skin to accommodate the internal receiver-stimulator portion of the implant. This part of the implant has a very flat design so that it will not produce a noticeable deformity.


An opening is then made into the air-filled bone called the mastoid. This mastoidectomy allows us to access the cochlea without disturbing the ear canal or eardrum. A very small opening is made into the cochlea, and the implant electrode is threaded in as far as possible. Most cochleas can accommodate the complete electrode unless there is a cochlear abnormality, which may result in a partial insertion.


The incision is closed with hidden absorbable stitches that do not require removal. A mastoid dressing is placed on the ear and remains in place for 1 to 2 days. Patients usually leave the hospital 2 to 3 hours after surgery is completed. Pain is mild-to-moderate for 1 to 2 days and can be controlled with oral pain medicines. Some patients experience imbalance for a few days after surgery, but this resolves within the first week.


Patients are seen in the office 1 week after surgery to check the incision. Most patients are able to return to work or school at that point. The initial activation of the device and placement of the external equipment is performed 4 weeks after surgery. Once healed, there is practically minimal visible evidence of the implant’s presence. The incision can tolerate water 3 days after surgery. Sports and strenuous exercises should be suspended for 3 weeks. After that, there are no activity restrictions.


Cochlear implants are extremely reliable. It is expected that a patient will never need to have their implant replaced. Less than 1% of implants have malfunction that requires replacement. Thankfully, if necessary, implants can be surgically replaced without losing any hearing performance. This also means that in the future patients can be upgraded to newer technology if warranted by the expectation of improved performance.


Examples of external components from the three manufacturers are seen below:

Image of cochlear implants external components

Other considerations

Each patient will have an ID card identifying that they have implanted medical technology. The degree of MRI compatibility has some variance currently between each manufacturer. Issues related to MRI and cochlear implants should be discussed with your cochlear implant surgeon.

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