Cochlear Implants

Introduction

A cochlear implant is a small electronic device that assists in providing a sense of sound to an individual who is profoundly deaf or severely hard-of-hearing. The implant consists of an external portion, located behind the ear, and an internal portion, surgically positioned underneath the skin.

Who might need a cochlear implant?

  1. Auditory Evaluation
    1. A child with hearing loss that is not improved enough with a hearing aid or other amplification device
    2. The patient can present as a prelingual or postlingual child depending on whether the hearing impairment was congenital or acquired.
    3. Newborn screening tests pick up approximately 12,000 patients who have hearing impairment shortly after birth, and others are generally picked up due to screening or concerns brought up by parents.
    4. All patients who might be candidates for cochlear implants should undergo detailed evaluation for the exact etiology of their hearing impairment and to ascertain what interventions, if any, will increase their quality of life.

 

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  1. Medical evaulation: The pediatrician must determine that the benefits of a cochlear implant surgery outweigh the risks of the procedure and that the patient has no absolute contraindications to anesthesia. Most otherwise healthy patients with hearing loss will usually benefit from a cochlear implant.
  2. Psychosocial/Rehabilitation Evaluation: Families must be counseled for the range of outcomes that occur after placement of the device and counseled on the intense rehabilitation that should follow implantation. Patients in need of resources for proper rehabilitation should be referred to help provide the child with support.

Devices

Three devices currently are FDA-approved in children and they all have the following features in common.

  1. All are multichannel devices that arrange multiple electrodes within the cochlea in order of the frequencies of sound they transmit that align with the frequencies of the sounds that the cochlea would normally transmit. This is called tonotopic arrangement.
  2. All have an external transmitting device that communicates with the cochlear implant using a magnet. No wires or hardware connects the external device with the internal device.
  3. All can have telemetry capabilities to assess for proper functioning
  4. Each device has a variety of speech processing options
  5. Each device has individualized programming capabilities to tailor the implant to the specific goals of the patient.

How the devices work:

  1. The external microphone picks up sound waves
  2. The sound information is coded and transmitted across the skin to the receiver in the mastoid bone
  3. The electrodes carry that information to the cochlea and stimulate the auditory nerve
  4. The auditory nerve carries the signals that it received from the cochlea to the brain, there further processing and the perception of sound takes place

Surgery:

  1. Anesthesia type: General
  2. Length: 2-4 hours of procedure with usually 1 overnight stay or as an outpatient if  required by insurance
  3. Considerations: Ossification secondary to meningitis and malformed cochlear anatomy (Mondini deformity) may necessitate a different approach.
  4. Animated video of surgical approach


www.youtube.com/watch?v=LZ66GhTxCD8

Device Programming:

  1. 3-5 weeks after implantation, the external device is fitted and the device is programmed
  2. Thresholds - minimum threshold of sound resulting in cochlear stimulation. This is set to allow for sufficient hearing of quiet sounds.
  3. Comfort Level - maximum threshold of sound that results in cochlear stimulation. This is set to prevent too much sound transmission causing pain/discomfort.

Complications:

Immediate Risks:

  1. Postoperative bleeding, infection, effects of general anesthesia
  2. Facial nerve injury
  3. Postoperative dizziness

Longterm Risks:

  1. Infection, meningitis
  2. Device failure in approximately 2% of patients, requiring reimplantation
  3. Device migration/extrusion, requiring reimplantation
  4. Facial nerve stimulation, which usually is ameliorated by alterations in device programming

Outcomes:

  1. Speech perception abilities in children who received cochlear implants was equal to or superior to the abilities in children who used hearing aids
  2. Earlier implantation results in better results for children with deafness (prior to approximately 2-3 years old)
  3. Children who receive cochlear implants derive speech, language, and reading benefits
  4. Auditory and oral training rehabilitation after implantation is important during the critical period of aural development.

References:

  1. American Academy of Audiology. Cochlear Implants in Children. (2015) http://www.audiology.org/publications-resources/document-library/cochlear-implants-children
  2. American Speech Language Hearing Association. Technical Report: Cochlear Implants. (2015) http://www.asha.org/policy/TR2004-00041/#sec1.3
  3. CDC. “What’s your baby’s hearing screening result?” (2015) http://www.cdc.gov/features/newbornhearing/
  4. Cochlear Implants. Kids Health Org. (2015) http://kidshealth.org/parent/general/eyes/cochlear.html
  5. Cohen, N. L. (2000). Surgical techniques for cochlear implants. In S. B. Waltzman & N. L. Cohen (Eds.), Cochlear implants (pp. 151–156). New York: Thieme Medical Publishers.
  6. Geers, A. (2002). Factors affecting the development of speech, language and literacy in children with early cochlear implantation. Language, Speech, and Hearing Services in Schools, 33, 173–184.
  7. Gheorghe DC, Zamfir-Chiru-Anton A. Complications in cochlear implant surgery. J Med Life (2015)
  8. Kirkham E, Sacks C, Baroody F, Siddique J, Nevins ME, Woolley A, Suskind D. Health Disparities in pedaitric cochlear implantation: an audiologic perspective. Ear Hear (2009)
  9. NIH. Cochlear Implants. National Institute on Deafness and Other Communication Disorders. (2015) http://www.nidcd.nih.gov/health/hearing/pages/coch.aspx#c
  10. Papsin B, Gordon K. Cochlear Implants for Children with Severe-to-Profound Hearing Loss. NEJM (2007)
  11. Rubin LG, Papsin B. Cochlear Implants in Children: Surgical Site Infections and Prevention and Treatment of Acute Otitis Media and Meningitis. American Academy of Pediatrics (2010)
  12. Singleton AJ, Waltzman SB. Audiometric Evaluation of Children with Hearing Loss. Otolaryngol Clin North Am (2015)

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