Indications for Cochlear Implants

Updated: Jan 28, 2016
  • Author: Kenneth H Lee, MD, PhD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Hearing loss is one of the most common sensory impairments and affects 28 million Americans. Approximately 1-3 out of 1000 newborns has hearing impairment. The elderly are more commonly affected with 40-50% of people over age 75 having hearing loss. Depending on the degree of hearing loss, many affected individuals can be successfully fitted with hearing aids. For patients with hearing loss that is not mitigated with hearing aids, a cochlear implant may provide an opportunity for hearing. [1]

The cochlear implant is a surgically placed device that converts sound to an electrical signal. This electrical signal is transmitted via electrodes to the spiral ganglion cells in the cochlear modiolus. As of 2012, an estimated 324,000 patients worldwide have received cochlear implants. However, this number represents only a small number of individuals with hearing impairment who may potentially benefit from implantation. Many candidates for cochlear implants often do not have access to this procedure due to failure of recognizing appropriate candidates or because of inadequate healthcare resources.

Although individual responses to cochlear implants are highly variable and depend on a number of physical and psychosocial factors, the trend toward improved performance with increasingly sophisticated electrodes and programming strategies has dramatically expanded indications for cochlear implantation. Although cochlear implants originally were touted as an aid to speech reading for individuals with profound hearing impairment, a growing population of implanted patients are exceeding their preoperative hearing performance (which was aided with conventional hearing aids). Due to the overall success of cochlear implants and ongoing advances in performance, an article addressing indications for cochlear implantation attempts to describe a target that moves almost yearly.

For patient education resources, see the Ear, Nose, and Throat Center, as well as Hearing Loss.

An image depicting labyrinthitis ossificans can be seen below.

Labyrinthitis ossificans. Cochlea on the left is o Labyrinthitis ossificans. Cochlea on the left is obliterated by bone after meningitis. Scala tympani of the cochlea on the right was patent, and the patient underwent successful implantation with complete electrode insertion.


Throughout the 1970s, the Food and Drug Administration (FDA) recommended that devices be implanted only in adults with profound hearing loss. In 1986, the FDA allowed children at least 2 years of age to be implanted. The age limit has recently been lowered to 12 months for all 3 devices available in the United States (Advanced Bionics, Med-El, and Cochlear Corporation devices). Over time, indications have been broadened to include adults with severe hearing loss who may achieve some benefit from conventional amplification.


Preoperative Considerations

Cochlear implantation is a collaborative effort involving patients, families, schools, audiologists, speech/hearing therapists, and surgeons. A patient with hearing impairment does not have a surgical problem that responds to the simple intervention of an implant surgeon. Because preoperative expectation affects the patient's postoperative satisfaction and use of the implant, all patients and families require attention and counseling from an implant team before they embark on the life-changing journey of cochlear implantation.

Pure-tone audiometry

The human ear is capable of hearing frequencies from 20-20,000 Hz. Pure-tone audiometry is used to assess a subject's response to a frequency at a specific intensity measured in decibels. In most cases, frequencies from 250 Hz to 8000 Hz are assessed, as these are most important for speech perception.

Speech audiometry

Although a number of speech-recognition tests are currently used for different reasons, one of the most common speech-recognition tests is the hearing in noise test (HINT), which tests speech recognition in the context of sentences. In determining cochlear implant candidacy, HINT is performed without background noise, despite its name. HINT measures word-recognition abilities to assess the patient's candidacy for cochlear implantation, in conjunction with conventional pure-tone and speech audiometry. The HINT consists of 25 equivalent 10-sentence lists that may be presented in quiet or noise to assess the patient's understanding of sentences.

As noted earlier, when used to assist in the determination of cochlear implant candidacy, the HINT is currently performed in quiet. (HINT sentences are found in the Minimum Speech Perception Test Battery for Adult Cochlear Implant Users CD.) Administer the first test in quiet by using 2 lists of 10 sentences, which are scored for the number of words correctly identified.


For adults and children who can respond reliably, standard pure-tone and speech audiometry tests are used to screen likely candidates. For children aged 12-23 months, the pure-tone average (PTA) for both ears should equal or exceed 90 dB. For individuals older than 24 months, the PTA for both ears should equal or exceed 70 dB. If the patient can detect speech with best-fit hearing aids in place, a speech-recognition test in a sound field of 55-dB HL sound pressure level (SPL) is performed. A number of speech recognition tests are currently in use.

Current US Food and Drug Administration (FDA) guidelines permit implantation in patients whose open-set sentence recognition (eg, HINT) is 60% or less in the best-aided condition. However, for patients receiving Medicare benefits, the current cutoff for cochlear implant candidacy is a HINT score of 40% or less. For Medicare patients enrolled in an acceptable clinical trial or study, the cutoff is 60% or less. Guidelines for other third-party payers may vary and should be consulted.

Many centers have replaced HINT sentences with AzBio sentences based on the findings of Gifford (2008). Gifford compared HINT sentences, AzBio sentences, and CNC words in hearing-impaired patients with and without cochlear implants. Unlike AzBio sentences, HINT sentences were found to have a poor correlation with CNC words and had a significant ceiling effect. [2]

Other tests

In children with prelingual deafness, cochlear implant candidacy is established when auditory skills fail to develop after amplification and aural rehab over a 3-month time period. Progress is typically monitored with the Meaningful Auditory Integration Scale or the Early Speech Perception test. Other scales of auditory benefit may be used in older children.


Imaging with CT or MRI is performed prior to implantation to evaluate the inner ear, facial nerve, cochleovestibular nerve, brain, and brainstem. MRI may reveal hypoplasia or aplasia of the cochleovestibular nerve, whereas CT may show a narrow internal auditory canal or absence of the bony cochlear nerve canal at the modiolus. Inner ear malformations ranging from the rare cases of cochlear aplasia to the more common enlarged vestibular aqueduct are easily visualized on CT or MRI. Such results may alter the choice of side of implantation or raise other issues such as electrode selection.

Patients with cochlear malformations are still candidates for cochlear implantation, but they may require a different type of electrode, a different surgical approach (ie, drill out), and may be more at risk for meningitis or cerebrospinal fluid gusher. Surgeons should be prepared for a cerebrospinal fluid leak caused by incomplete partition between the cochlea and the internal auditory canal. Absence of the cochlea or the cochlear nerve can usually be confirmed with imaging and are absolute contraindications for cochlear implantation.

Clinicians must take extra caution to identify the cochleovestibular nerve complex; auditory stimulation with a cochlea implant in patients with supposed cochlear nerve aplasia has been reported. These cases may be more appropriately labeled cochlear nerve hypoplasia. Families and patients must be adequately counseled and fully informed about the variable performance of patients with dysplastic cochleae and the potential risk of cerebrospinal fluid leakage and meningitis.

In pediatric or young adult patients with progressive hearing loss, exclude neurofibromatosis II by performing MRI before proceeding with implantation. MRI has more recently become the imaging study of choice at some institutions because the inner ear, cochleovestibular nerve, brain, and brainstem can all be visualized. MRI, unlike CT scanning, is also very useful in identifying early labyrinthitis ossificans, which typically begins with endoluminal fibrosis of the scala tympani at the basal turn.

Preoperative counseling and education

In addition to the purely audiologic criteria discussed above, pediatric candidates must be enrolled in an educational program that supports listening and speaking with aided hearing. For patients of all ages, no medical contraindications (eg, cochlear or auditory nerve aplasia, active middle-ear infection) may be present. Communication among patients, families, schools, audiologists, therapists, and surgeons is required.


A study published in 2003 reported that pediatric and adult patients with cochlear implants are at increased risk of acquiring S. pneumoniae meningitis. [3] In 2002, the CDC issued age-appropriate immunization guidelines for patients who have a cochlear implant or are going to be the recipient of a cochlear implant. These vaccines include the 13-valent pneumococcal conjugate vaccine (PCV13; Prevnar), and the 23-valent pneumococcal polysaccharide vaccine (PPV23; Pneumovax).

The following recommended schedule was recommended:

  • Children aged less than 24 months with cochlear implants should receive PCV13. If a vaccination is missed, the appropriate catch-up schedule should be used.
  • Children aged 24 to 59 months with cochlear implants who have not received PCV13 should be vaccinated according to the high-risk schedule. Children who have missed a vaccination should be vaccinated according to the catch-up schedule. PPV23 should be given to children 2 months after they have completed the PCV13 series.
  • Patients between the ages of 5 and 64 with cochlear implants should receive PPV23.
  • An age-appropriate pneumococcal vaccination series should be completed at least 2 weeks before surgery (see Table).

Table. Recommended Pneumococcal Vaccination Schedule for Persons With Cochlear Implants (Smith PJ, Nuorti JP, Singleton JA, et al.) (Open Table in a new window)

Age at First PCV13 Dose


PCV13 Primary Series PCV13 Additional Dose PPV23 Dose
2-6 3 doses, 2 months apart† 1 dose at 12-15 months of age§ Indicated at ≥ 24 months of age ¶
7-11 2 doses, 2 months apart† 1 dose at 12-15 months of age§ Indicated at ≥ 24 months of age ¶
12-23 2 doses, 2 months apart** Not indicated Indicated at ≥ 24 months of age ¶
24-59 2 doses, 2 months apart** Not indicated Indicated¶
≥60 Not indicated† † Not indicated† † Indicated
*A schedule with a reduced number of total 13-valent pneumococcal conjugate vaccine (PCV13) doses is indicated in children who start late or are incompletely vaccinated. Children with a lapse in vaccination should be vaccinated according to the catch-up schedule. [4]

† For children vaccinated at less than 1 year, the minimum interval between doses is 4 weeks.

§The additional dose should be administered at 8 or more weeks after the primary series has been completed.

¶Children older than 5 years should complete the PCV13 series first; 23 variant pneumococcal polysaccharide vaccine (PPv23) should be administered to children 24 months and older 8 weeks or more after the last dose of PCV13. [5]

**The minimum interval between doses is 8 weeks.

† † PCV13 is generally not recommended for children 5 years and older.


Etiologies of Severe to Profound Hearing Loss


Genetic hearing loss is the most common etiology of childhood deafness (33-50%); and many of these cases can be attributed to single gene mutations. Seventy five to eighty percent of genetic deafness is secondary to autosomal recessive gene defects, 18-20% is secondary to autosomal dominant gene defects, and the remainders are X-linked gene defects. Another potential cause of genetic deafness is mitochondrial gene defects. Genetic hearing loss is generally divided into nonsyndromic and syndromic, with the former being twice as common as the latter.

To date, 25 autosomal recessive loci, 21 autosomal dominant loci, and 1 x-linked loci have been reported for nonsyndromic hearing loss. The GJB2 gene encodes for the protein Connexin 26, and mutations in GJB2 account for the most common cause of nonsyndromic autosomal recessive deafness, which is thought to be responsible for 20% of hereditary hearing loss in children. Connexins are transmembrane proteins that form gap-junction channels. These channels allow ion transport and cell-to-cell communication. Syndromic hearing loss conditions include but are not limited to Waardenburg, Stickler, Brachio-oto-renal, Treacher Collins, Neurofibromatosis, Usher, Jervell Lange-Neilsen, Alport, and Pendred syndromes.


See the list below:

  • Nonmeningitis
    • Nongenetic or environmental causes generate 25-33% of childhood deafness. Congenital cytomegalovirus is the most common environmental cause of hearing impairment in children.
    • Ten to fifteen percent of patients with asymptomatic congenital CMV infections develop mild to profound sensorineural hearing loss. Other potential infectious agents include rubella, syphilis, toxoplasmosis, mumps, and measles.
  • Meningitis
    • Meningitis causes approximately 9% of childhood deafness and can make implantation difficult. Organisms commonly causing meningitis (from most to least common) include Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis.
    • The organism causing the highest incidence of hearing loss is S pneumoniae (31%). Patients with meningitis are predisposed to developing obstruction of the cochlear lumen (ie, labyrinthitis ossificans; see the image below), especially when S pneumoniae is the causative organism.
      Labyrinthitis ossificans. Cochlea on the left is o Labyrinthitis ossificans. Cochlea on the left is obliterated by bone after meningitis. Scala tympani of the cochlea on the right was patent, and the patient underwent successful implantation with complete electrode insertion.

Although 12 months is the current age limit the FDA has established for implantation, other factors may cause the implant team to treat infants younger than 12 months. In particular, a child with deafness due to meningitis may develop labyrinthitis ossificans, filling the cochlear duct or the entire cochlear labyrinth and usually the scala tympani starting near the round window, with bone. In cases of labyrinthitis ossificans, special techniques may be needed for successful cochlear implantation. However, even with special techniques, this condition often leads to a suboptimal outcome.

The image above depicts a CT scan of a child with deafness due to meningitis whose left cochlea has ossified. In this patient, successful implantation of the patent right cochlea was accomplished. For patients at risk of labyrinthitis ossificans, implantation may be indicated soon after early ossification or fibrosis is diagnosed. Early implantation in the setting of labyrinthitis ossificans may allow a full electrode insertion and obviate the need for performing a cochlear drill-out procedure.

Using serial imaging, implant teams may monitor patients with new deafness due to meningitis and perform implantation at the first sign of replacement of the scala tympani with fibrous tissue or bone. Several reports have described spontaneous hearing improvement after meningitis in patients with residual hearing. In patients with profound hearing loss after meningitis, the chance of hearing improvement is unlikely and cochlear implantation should proceed as soon as possible. Ossification can begin as early as 2 weeks after meningitis. In the setting of bilateral labyrinthitis ossificans, expeditious placement of bilateral implants should be considered as these patients are not likely to benefit from future technology.


Numerous medications can cause hearing loss. Perhaps the most well known ototoxic medications are the aminoglycoside antibiotics. Other commonly cited ototoxic medications include loop diuretics, erythromycin, salicylates, vancomycin, cisplatin, and quinine.


Hearing loss from temporal bone trauma is most commonly conductive secondary to hemotympanum, tympanic membrane perforation, or ossicular discontinuity. The otic capsule is fairly resistant to trauma but occasionally fractures may involve the cochlear or labyrinth. Injuries to the otic capsule almost always results in profound sensorineural hearing loss. Bilateral otic capsule fractures are very uncommon but would be an indication for cochlear implantation. Intraluminal fibrosis or ossification may occur in the setting or otic capsule fractures, which can make electrode insertion more difficult. Preoperative imaging may provide additional information of fibrosis or ossification has occurred.


In the setting of neonatal jaundice, bilirubin may cross the blood-brain barrier. Bilirubin can deposit in the ventral cochlear nucleus and cause sensorineural hearing loss. Transient loss of wave IV and V on an auditory brainstem response (ABR) is seen in 33% of neonates with bilirubin levels of 15-25 mg/dL. Hyperbilirubinemia is also a risk factor of auditory neuropathy.

Auditory neuropathy/dyssynchrony

Patients with auditory neuropathy are characterized by intact outer hair cell function with abnormal or absent ABR, implicating the vestibulocochlear nerve as the site of pathology in this condition. Outer hair cell function can be assessed with otoacoustic emissions, the cochlear microphonic or pure-tone audiometry. A defect in inner hair cells, spiral ganglion cells or the synapse between the two is the cause of auditory neuropathy.

Auditory neuropathy occurs in both adults and children. Pure-tone audiometry may reveal normal to profound hearing loss, but poor performance of speech discrimination testing is the common denominator in patients with auditory neuropathy. Anoxia, hyperbilirubinemia, and prematurity are potential risk factors for auditory neuropathy. Several recent reports described hereditary forms of auditory neuropathy, including a nonsyndromic autosomal dominant condition that progresses to outer hair cell involvement with eventual decline of pure-tone hearing. Some patients may benefit from FM devices or hearing aids, but in some cases a cochlear implant may provide the only means to communicate.

Ménière disease

Meniere disease is characterized by room spinning vertigo, fluctuating hearing, tinnitus, or aural fullness. The diagnosis is made with a thorough history and physical examination, as well as imaging studies to rule out retrocochlear pathology. Histology of postmortem temporal bones in subjects with Meniere disease reveals dilation of the endolymph compartment. Histologic endolymphatic hydrops may be the end result of some other pathologic process that is causing the symptoms of Meniere disease or may be the actual cause of the symptoms.

A recent study showed 11% of patients presented with bilateral disease and another 12% eventually developed symptoms in their unaffected ear. [6] The progression of hearing loss is difficult to predict but may result in bilateral profound loss. A recent series of 9 patients with bilateral Ménière disease who underwent cochlear implant showed overall excellent performance results with at least one year of follow-up. Some patients in this series experienced fluctuations in their implant performance associated with episodic vertigo attacks.

Noise-induced hearing loss

According to the National Institute of Deafness and Communication Disorders, 10 million American have noise induced hearing loss and an additional 30 million are exposed dangerous noise levels daily. [7] Hearing loss secondary to noise exposure can be temporary (temporary threshold shift) or permanent (permanent threshold shift). Acoustic trauma is the immediate, permanent onset of hearing loss after exposure to sounds louder than 140 dB, such as explosions or firearm discharge. Outer hair cells are the most susceptible to noise exposure. The outer hair cells typically swell with excessive noise exposure, but may normalize if the noise exposure ceases. A notch at 4000 Hz on pure-tone audiometry is fairly common in the setting of noise-induced hearing loss, but hearing loss may progress to a level where even amplification provides little benefit.


Hearing loss associated with aging initially begins with loss of high frequencies, with eventual progression to include lower frequency loss. Thirty to thirty five percent of 65 year olds have some hearing loss; this figure rises to 40-50% of individuals over 70 years. Men are more commonly affected with age-related hearing loss. Hearing aids often provide meaningful benefit for patients with presbycusis, but only one in five individuals who would benefit from a hearing aid actual wear one. Patients with severe to profound hearing loss who are unable to hear with traditional amplification may benefit from a cochlear implant. In cases where residual low frequency hearing is found, some individuals may benefit from a combined hearing aid /cochlear implant that provides both electrical and acoustic stimulation.


Bilateral Implants

Patients with unaided unilateral hearing loss often have difficulty in everyday listening situations. Significant disadvantages to unilateral hearing loss are well known and include the head shadow effect, difficulty with hearing in noise, and sound localization. Amplification for unilateral hearing loss is routinely recommended in children and adults. A multitude of studies have demonstrated significant performance improvement in patients with bilateral cochlear implants.

A number of arguments have been made against bilateral implantation, including saving the ear for future technology or using a hearing aid with residual hearing. No one knows when future technologies (ie, gene therapy) will become available for clinical use, and a critical time period for auditory development remains. A recent study showed that a second critical time period in regards to bilateral implantation may exist. Significant delay between the first and second implant may significantly decrease future benefit. [8] A formal position statement supporting bilateral cochlear implants as accepted medical practice has been issued by the William House Cochlear Implant Society. This position statement was issued after pertinent literature was reviewed in regards to bilateral cochlear implants. [9, 10]



Critical outcome factors for pediatric patients receiving implants include (1) age at onset of deafness and duration of deafness prior to implantation, (2) progression of hearing loss, and (3) educational setting.

In general, early implantation facilitates rapid development of oral communication ability. Progressive hearing loss, which allows for the development of speech-reading skills, favors performance after implantation. Placement in a school setting that stresses oral versus signed communication is important for optimal implantation outcome. However, many variables remain unknown because approximately one half of the variance in performance after implantation cannot be predicted.

Children should be receptive to wearing a hearing aid before cochlear implantation because all current implants require an external processor. A period of hearing aid use to ascertain development of aided communication ability is an important criterion in determining candidacy of young children.

After audiologic criteria have been met, parental expectations and attitudes must be assessed and addressed. Unrealistic expectations can frustrate the efforts of the child and the implant team. Families must be appropriately counseled about the need for long-term therapy, variable outcome of implantation, and the limitations of implantation.

A study by Dillon et al indicated that revision cochlear implantation should not be contraindicated by older age. The study, of 14 adults under age 65 years and 15 patients aged 65 years or older, all of whom underwent revision cochlear implantation, found improvements in speech perception performance tests in both groups at 3 and 6 months postrevision, compared with prerevision results, with no relationship found between age and performance scores. [11, 12]

A literature review by Terry et al found that severe complications following cochlear implant surgery are rare but nonetheless possible, even years after the operation. With follow-up ranging from 1 month to 17 years, the investigators found that the rate of delayed complications was 5.7%. Vestibular complications were the most common (3.9%), with device failure (3.4%) and taste problems (2.8%) being the next most frequent. The report suggested that patients with cochlear implants receive lifetime follow-up. [13, 14]



Tinnitus is an abnormal perception of sound that currently affects approximately 10% of the population. A subset of patients will pursue active treatment for their tinnitus in cases in which it has significantly reduced their quality of life. Tinnitus retraining therapy is one of the few proven treatment options available to patients experiencing severe tinnitus. The expense, duration of therapy, and limited number of programs offering tinnitus retraining therapy leaves a significant number of patients with severe tinnitus without a viable treatment option.

Several studies have revealed that adult cochlear implant recipients with preoperative tinnitus have noticed either reduction or abolition of their tinnitus while wearing their cochlear implant. [15, 16] A recent study showed a significant reduction or cessation of tinnitus in 20 out of 21 patients with single-sided deafness who were implanted for severe tinnitus. Three of the patients in this series displayed permanent residual inhibition (ie, no evidence of tinnitus even while not wearing their processor). To date, cochlear implantation appears to be one of the more successful treatment options for severe tinnitus. [15]


Unilateral deafness

Patients with unilateral deafness are unable to localize sound, have difficulty hearing in the presence of background noise, and have increased listening effort. Currently available rehabilitative strategies for unilateral deafness all utilize the intact ear via contralateral routing of sound using a CROS hearing aid or a bone-anchored hearing aid. The aforementioned therapies provide significant benefit for a number of patients with unilateral deafness with respect to the head shadow effect and in select situations of background noise. Sound localization and hearing in significant background noise requires a normal to near-normal binaural hearing. [17]

Several studies have examined the outcomes of unilaterally deaf patients who underwent a cochlear implant for the primary indication of severe tinnitus. These patients did not have any evidence of improvement in summation effect, but did have improved speech recognition with respect to the head shadow effect. Sound localization in patients with normal hearing in the intact ear improved when assessed indirectly via a questionnaire. [16]

At present, cochlear implantation in patients with unilateral deafness without tinnitus is not indicated based on the limited available evidence.


Residual hearing

The first hybrid cochlear implant system was approved by the US Food and Drug Administration (FDA) in March 2014 for patients aged at least 18 years. The hybrid implant has a short implant electrode array that reduces the risk of losing residual low frequency hearing in patients with profound high-frequency loss. A small cochleostomy is created, and the short electrode array is slowly inserted into the inferior basal turn of the cochlea. The use of a short electrode array reduces the risk of intracochlear trauma, which increases the likelihood of preserving residual hearing. The preserved low-frequency hearing can then be amplified with a hearing aid built into the speech processor.

This approach allows for the auditory rehabilitation of patients who are not candidates for conventional implants because their low-frequency hearing exceeds current guidelines. Hearing preservation after cochlea implantation often results in improved melody and instrument recognition, better frequency resolution, and improved hearing in noise. [18]