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Criteria for Cochlear Implantation
 Figure 1. Number of cochlear implants performed at MUSC
Cochlear implants have been widely accepted as a treatment option for patients with severe-to-profound sensorineural hearing loss (SNHL) for more than 20 years. Many would argue that a cochlear implant represents the "gold standard" for these patients for enhancing communication. Worldwide, well over 200,000 individuals have received cochlear implants, but the number of potential candidates is in the millions.
Adults who have lost their hearing after acquiring language (postlingually deafened) benefit significantly from cochlear implants. Children who are postlingually deafened and receive a cochlear implant also benefit significantly from the device. The group who might benefit the most from communication with a cochlear implant are children who were born with little to no hearing or who lost hearing at a very young age before developing significant language (prelingually deafened). Ninety percent of children with prelingual profound SNHL, whether from genetic, acquired, or another cause, are born to parents who hear. In 2012, many of the families of these children decide that they want their child to hear with the help of a cochlear implant.
In general, to be considered as a candidate for a cochlear implant, a patient must:
* have severe-to-profound sensorineural hearing loss
* not receive significant benefits from hearing aids
* be relatively healthy and free from significant surgical risk factors
* and not have significant anatomical contraindications to the placement of a cochlear implant, such as an absent cochlea or an absent cochlear nerve.
The patient and/or family should have reasonable expectations about the surgery and long-term performance with the device.
These broad criteria have not changed very much since the dawn of cochlear implantation. Several things have changed, however. Today's cochlear implants and the speech processors provide for levels of performance that are significantly higher than older devices. Children are being implanted at earlier ages, and performance for the younger children outpaces performance for the children implanted at older ages. Both adults and children with more residual hearing than was allowed in the past are receiving cochlear implants, and performance, in general, for patients with more hearing outpaces performance for patients with less hearing.
The FDA determines guidelines for cochlear implantation. Current regulations allow for a patient to identify up to 50% of the words presented in sentences under best-aided conditions. Performance on sentence recognition tests corresponds moderately well to scores on monosyllabic word tests such as those routinely obtained in standard audiological testing in the clinic (NU-6, CID, or PB word lists). Words in sentences are often significantly easier to understand than words in isolation. When a patient demonstrates poor performance on word recognition tests in the clinic, the clinician should consider referring the patient to a cochlear implant center, such as MUSC, for further testing to determine whether she or he can be considered for a cochlear implant. For example, if a patient obtains less than 40-50% of the words on typical monosyllabic word recognition testing in the clinical setting, s/he should be referred for a cochlear implant evaluation to determine if s/he meets criteria for implantation.
Medicare also determined guidelines for cochlear implantation for patients with Medicare. Medicare is more strict than the FDA in its criteria for cochlear implantation. Current regulations allow for a patient to identify up to 40% of the words presented in sentences under best-aided conditions.
For the adult population, there is not an upper age limit for cochlear implantation. Most large cochlear implant centers in the United States, such as MUSC, have implanted patients over the age of 90 with excellent success. Many patients in this age range are quite healthy, and they can undergo a short outpatient procedure such as cochlear implantation without difficulty. With an elderly patient, or a patient with medical problems, the patient should be evaluated before surgery by the anesthesiology team and any other specialists deemed appropriate, such as a cardiologist.
In general, for children, age is not a criteria for cochlear implantation. Twelve months is the lower limit set forth by the FDA. Some insurance companies do not allow for cochlear implantation in children under the age of 12 months, based on the FDA guidelines. However, most large centers in the United States, such as MUSC, have implanted many children under the age of one year.
It has been demonstrated that children implanted between the ages of 2 and 3 years perform better in the long run than children implanted between the ages of 4 and 5 years. It also appears that children implanted between the ages of one and two perform even better with their devices than older children. It has yet to be clearly demonstrated that children implanted under the age of 12 months perform significantly better than children implanted over the age of 12 months. But I suspect that this will eventually be demonstrated.
To be considered a candidate for a cochlear implant, adults and children should have severe-to-profound sensorineural hearing loss. They should not obtain significant benefit from hearing aids. This is usually relatively easy to determine in an adult, but it can be somewhat difficult to determine in a young child, especially for professionals without a great deal of experience with children with hearing loss. Children, just like adults, are not required to have no hearing, and both children and adults can have too much hearing to be considered for a cochlear implant. Through evaluations by an audiologist and a speech-language pathologist, it must be demonstrated that the child's hearing is poor and that progress in language development is poor with proper amplification for consideration for a cochlear implant.
All patients considered for a cochlear implant should be relatively healthy. The procedure, in general, lasts around 2 hours. Blood loss is usually minimal. The majority of patients can have surgery on an outpatient basis. This is not much different than having another ear surgery. Almost all patients have surgery for a cochlear implant while under general anesthesia. Patients can be dizzy after surgery, and this usually diminishes rapidly with time.
Most patients have either a CAT scan or an MRI scan prior to surgery to evaluate the anatomy of the inner ear and to search for contraindications to having surgery. A CAT is excellent at demonstrating the anatomy of the inner ear, but it does not show the level of detail as does the MRI scan when evaluating the auditory nerve. Patients who have heard and have lost hearing have a cochlear nerve, and an MRI scan is not absolutely necessary. If the patient lost hearing from meningitis, however, the cochlea can become ossified with new bone growth. If the cochlea is completely ossified, cochlear implantation might prove difficult if not impossible. An MRI might help the surgeon determine whether a cochlear implant is possible. Patients who are found to have a tumor that can cause hearing loss on an MRI scan may not be cochlear implant candidates either. Children who hear minimally can normally have a CAT scan to evaluate the anatomy of their inner ears, rather than an MRI scan. However, many centers routinely perform MRI scans on children with hearing loss, especially in children who do not appear to hear anything. The anatomy of the inner ear is evaluated with both the CT and the MRI, and the MRI is helpful in determining the status of the cochlear, or auditory, nerve. If the patient does not have an auditory nerve, then a cochlear implant will not be able to stimulate the absent nerve to allow for hearing.
Patients and family members must have reasonable expectations to obtain a cochlear implant. A cochlear implant does not provide a patient with normal hearing. For post-lingually deafened adults, a cochlear implant often provides enough auditory information for the patient to talk on the telephone. A cochlear implant should provide enough information for a deaf child to develop spoken language, but this does not happen for all children. In all cases, whether an adult or a child, the patient with a cochlear implant must practice listening with the device. It is unrealistic to expect the patient to hear clearly the moment that the cochlear implant is activated although some patients hear quite well at this time.
Families of children with cochlear implants should be expected to participate in an ongoing speech therapy training program. A speech pathologist experienced with children with hearing loss and cochlear implants is an essential part of the cochlear implant aural rehabilitation process. Parents are also expected to spend a great deal of time with their children learning how to listen with a cochlear implant.
 Figure 2. Total number of MUSC Cochlear Implants.
The MUSC Cochlear Implant Center has performed nearly 600 cochlear implantations since the program's inception in 1989. Read more about MUSC's Cochlear Implant Center on our website.
FDA website
Ted A. Meyer, M.D.,Ph.D.
Assistant Professor, Otolaryngology - Head & Neck Surgery
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