Definition and Overview
A cochlear implant is one of the treatment options for patients with severe hearing loss. However, before this can be recommended, an evaluation will be carried out first to ensure that it can adequately address the patient's specific condition.
Cochlear implants were developed back in the 1970s, and they are implanted into the inner ear through a complex surgical procedure. The device is designed to restore a patient's ability to hear up to a certain extent even when the condition is deemed irreversible. It does not, however, restore normal hearing, but is known to work better than hearing aids.
The cochlear implant is made up of an external sound processor (receives sound and converts it into signals), a receiver, an electronics system, and an electrode array that send the signals to the cochlea, which is a part of the inner ear. From the cochlea to the brain, the auditory signals are transmitted as normal.
Who should undergo and expected results
A pre-implant evaluation is the first step towards getting a cochlear implant as it determines whether or not the patient is a good candidate for the said electronic device. It is also useful in educating the patient and/or his family (in case the patient is a minor) about cochlear implants and their use to help them make an informed decision as to whether to go ahead with the implants or not.
An evaluation for cochlear implants is potentially beneficial for patients suffering from severe and irreversible hearing loss, which can be caused by any of the following factors:
- Congenital hearing loss – This refers to hearing loss that already affects an infant from birth, as opposed to delayed-onset or acquired hearing loss.
- Tympanic membrane perforation
- Chronic otitis media, a middle ear infection
- Bacterial meningitis
- Post-viral meningitis
- Meniere disease, a disorder associated with fluid imbalance inside the ear
- Presbycusis, or an age-related decline in a person's hearing ability, particularly in relation to high frequencies
These conditions may cause a wide range of symptoms, including:
- Hearing loss
- Photophobia, or inability to tolerate light
- Phonophobia, or inability to tolerate loud noises
- Neck stiffness
- Balance problems
- Ear pressure
- Pain inside the ear
Cochlear implantation is also often considered if hearing aids have failed to improve the patient's hearing loss problem.
However, there are some cases wherein a cochlear implantation is not recommended. An example is hearing loss caused by problems with the hearing nerves, as this will hinder the cochlea in transmitting auditory signals to the brain, rendering the benefits of cochlear implants futile.
Patients who are aged 12 months and older can undergo an evaluation for cochlear implants as the procedure is generally safe. While some studies show that cochlear implantation may also be safe for babies younger than 12 months, further investigations are still being conducted to verify such claims.
How the procedure works
An evaluation for cochlear implants usually involves five steps, which may or may not all be conducted on the same day. In many cases, the entire evaluation process takes up to 2 days, as each step may require the expertise of a different doctor or specialist. These five steps are:
- Cochlear implant orientation – At the start of the appointment, the doctor orients the patient about cochlear implants, the implantation process and the cost of getting them as well as their risks and benefits.
- Audiological evaluation – A patient is first evaluated based on his hearing condition. This part of the visit will determine whether the patient needs or will actually benefit from cochlear implants or should consider less invasive alternatives such as high-powered hearing aids.
- Medical evaluation – To ensure that the patient can safely undergo the surgical procedure required in the cochlear implantation process, he also undergoes a medical evaluation. The evaluation looks into the patient's history of anesthesia use to find out whether he is allergic or responds negatively to anesthesia, and may also involve x-rays. It also checks for other health conditions that may disqualify a patient from undergoing the cochlear implantation process.
- Radiographic studies – Some radiologic scans may also be conducted during the evaluation. These include CT and MRI scans, both of which are significantly helpful in assessing the condition of the cochlea.
- Psychosocial evaluation – The last and final step in the evaluation is the psychosocial aspect, which checks whether the patient is psychologically prepared to undergo a cochlear implantation procedure. This evaluation is performed by psychologists.
Of these five steps, the most important is the audiological evaluation, which may involve several hearing tests, such as:
- Complete neuro-otologic exam
- Otolaryngologic examination
- Pure tone audiometry
- Auditory brainstem response (ABR) testing
- Otoacoustic emission (OAE) testing
Before the visit ends, the doctor will also briefly discuss the long-term implications of having cochlear implants placed, such as the need for long-term follow-ups, which the patient should be willing to commit to. He will then end the discussion by giving his recommendations as to whether cochlear implantation is an appropriate choice.
If the patient is cleared for the procedure and consents to it, he may begin choosing his preferred type of cochlear implant device, the differences of which will be explained to him, so he can proceed with the procedure.
Possible risks and complications
An evaluation for cochlear implants ensures that the said device is indeed the best treatment option for the patient and that it is implanted safely with the least amount of risk. Cochlear implantation is a complex surgical procedure that comes with certain risks, such as:
- Increased susceptibility for pneumococcal meningitis, which can easily be resolved with a pneumococcal vaccine after the evaluation
- Allergic reaction to anesthetics, which is why most patients also have to schedule an appointment with their anesthesiologist before the implantation
Given these possible risks and complications, a thorough evaluation of the patient's suitability for the procedure needs to be conducted for his best interests.
Limb CJ, Francis HW, Niparko JK. Cochlear implantation. In: Flint PW, Haughey BH, Lund LJ, et al, eds. Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia, PA: Elsevier Mosby; 2015:chap 160.
Sparreboom M, van Schoonhoven J, van Zanten BG, et al. The effectiveness of bilateral cochlear implants for severe-to-profound deafness in children: a systematic review. Otol Neurotol. 2010 Sep;31(7):1062-71. PMID: 20601922. www.ncbi.nlm.nih.gov/pubmed/20601922.