Cochlear Implants - Into a World of Sound

Here are some things that a cochlear implant provides a person with severe to profound deafness the ability to do:

• Hear conversations and environmental sounds at comfortable loudness levels
  
• Significantly improve lip reading skill, and in many cases, enable understanding of some speech without lip reading
  
• Understand others with less effort
  
• In some cases, use the telephone

How Does a Cochlear Implant Work?

The cochlear implant differs from traditional hearing aids in many ways. A cochlear implant system consists of a microphone, a signal processor, a signal coupler (transmitter and receiver), and an electrode array. The microphone and signal processor are worn outside the body.

Cochlear implantation involves surgical placement of the internal portion of the device into the patient. The internal receiver is placed under the skin behind the ear, and the electrode array is placed into the inner ear during a one- to two-hour operation. After healing, the patient is given the external component to wear. A magnet holds the transmitter over the surgically implanted internal receiver. A thin cord connects the microphone to the transmitter and to the speech processor. Cochlear Implant Surgery

Once programmed, the external speech processor captures sound and converts it into a digital signal. The processor sends the digital signal to the internal implant, which then converts the digital signal into an electrical signal. The electrical signal is transmitted via the electrode array inside the cochlea, and the auditory nerve is then stimulated to carry sound to the brain.

Image courtesy of Cochlear

How Natural Hearing Works: 1. Ear canal: Sound moves through the ear canal and strikes the eardrum. 2. Eardrum and bones: Sound waves cause the eardrum to vibrate, sending the bones in the middle ear into motion. 3. Inner ear: This motion causes the fluid inside the inner ear (cochlea) to move the hair cells. 4. Hearing nerve: Hair cells change the movement into electric impulses, which are sent to the hearing nerve into the brain; you hear sound.

Image courtesy of Cochlear

How a Cochlear Implant Works: 1. Sound Processor: External sound processor captures sound and converts it into digital signals. 2. Digital Signals: Processor sends digital signals to internal implant. 3. Electrode Array: Internal implant converts signals into electrical energy, sending it to an electrode array inside the cochlea. 4. Hearing Nerve: Electrodes stimulate hearing nerve, bypassing damaged hair cells, and the brain perceives signals as sound.

Who Will Benefit from a Cochlear Implant?

A cochlear implant device is an excellent alternative to conventional hearing aids when they are no longer providing adequate benefit to patients with severe to profound hearing loss. Candidacy criteria for a cochlear implant has broadened in recent years, so many people who previously were not considered candidates are now receiving cochlear implants with successful results. In many cases, implantation may be done for both ears, either simultaneously during the same surgery, or sequentially.

Based on the guidelines for cochlear implantation approved by the Food and Drug Administration (FDA), individuals
with the following typically receive benefit from a cochlear implant:

Adults who:

• Have severe to profound sensorineural hearing loss in both ears
  
• Gain little or no benefit from appropriately-fit hearing aids following an adequate period of training
  
• Have no medical or radiological contraindications
  
• Have high motivation and appropriate expectations

Children who:

• Are 12 to 24 months of age and have profound sensorineural hearing loss in both ears
  
• Are 24 months of age or older and have severe to profound sensorineural hearing loss in both ears
  
• Receive little or no benefit from hearing aids following an adequate period of training
  
• No medical or radiological contraindications
  
• Have a network of family support that has a high degree of motivation and appropriate expectations for the child
  
• Have an educational/rehabilitation program that emphasizes auditory skill development

What is the Evaluation Process to Determine Suitable Candidacy?

A team of professionals conducts an extensive evaluation to determine if an individual is a suitable candidate for a cochlear implant. The cochlear implant candidacy evaluation includes:

• An audiological evaluation by an audiologist.
• A medical evaluation by an otologist.
• A radiological evaluation, which includes CT and/or MRI scanning.
• For children: Educational, psychological, and speech and language evaluation.

Because obtaining a cochlear implant involves a surgical procedure, it is very important to ensure that candidacy requirements are met prior to proceeding with implantation. During the comprehensive evaluation process, a skilled cochlear implant audiologist will first determine the patient’s hearing thresholds across the frequency range. The patient’s hearing aids are then evaluated to ensure they are appropriate given the degree of hearing loss. If it is found that the patient’s current hearing aids are not adequately meeting the needs of the patient (e.g. not giving enough volume for their hearing loss), a trial period with different amplification may be initiated. Using appropriate amplification, further audiometric testing is conducted to determine how well the patient can understand speech at normal conversational levels. If the audiometric tests determine that the patient is a cochlear implant candidate, an appointment is scheduled to meet with Dr. Maw for further medical evaluation. Dr. Maw will order either an MRI or CT scan prior to surgery, and may request other medical testing to ensure there is no medical contraindication for cochlear implantation. Typically, surgery can be scheduled after all evaluations are completed.

The office of Dr. Jennifer Maw is unique in the Bay Area in that it offers implantation of all three FDA-approved cochlear implant devices. You are counseled regarding the individual features of the three devices. You have the opportunity to choose which device you would prefer although we make recommendations based on your particular situation.

Why are expectations so important?

One of the reasons that evaluating a patient for a cochlear implant is so comprehensive is that we cannot guarantee any individual person’s performance with a cochlear implant. Performance will vary depending on numerous factors, including, age at time of hearing loss, cause of hearing loss, length of severe to profound hearing loss, age at implantation, motivation, etc. While everyone who receives a cochlear implant benefits in some way, either because they are now able to hear environmental sounds at near normal loudness levels, or because they can talk on the phone, there is no way for us to know prior to the activation of the cochlear implant how any one person will perform.

Cochlear Implants Available in the USA

The Maestro and Tempo Med-El Corporation	Nucleus 5 Cochlear Corporation	The Harmony Advanced Bionics Corporation

If you are interested in finding out more about cochlear implants:

Contact one of the skilled cochlear implant audiologists at Dr. Maw’s office:

• Sarika Patil, Au.D (spatil@earassociates.com)
  
• Natalie Schmitt, Au.D. (nschmitt@earassociates.com)

Cochlear Implant Evaluation in Infants and Children

Hearing loss in infants is now diagnosed at a higher rate due to neonatal hearing screening programs. All newborn babies receive a hearing screening before they leave the hospital. Babies who fail the screening are referred for a diagnostic hearing evaluation.

As per the National Institute on Deafness and Other Communication disorders, approximately 12,000 new babies a year are diagnosed with a hearing loss. In the first few years of life, hearing is a critical part of a child’s social, emotional, and cognitive development.

As per US Food and Drug Administration guidelines, children between 12 and 24 months of age who have a confirmed profound hearing loss can be considered for implantation. Children with severe to profound losses can be implanted at 2 years of age if there is lack of speech and language development with hearing aids. The FDA guidelines recommend a 6 month hearing aid trial for children under 2 years of age to determine if the child is receiving adequate benefit from conventional amplification.

The audiologist plays a critical role in the decision making process of whether to implant a child. The audiologist is responsible for conducting the hearing tests, confirming the degree of hearing loss and choosing appropriate amplification for the child.

A cochlear implant evaluation in children includes an extensive evaluation by the audiologist, consultation by Dr. Jennifer Maw and often an evaluation by an auditory verbal therapist experienced in the evaluation and therapy of the listening ability and subsequent language development of children.

Extensive state-of-the-art diagnostic testing of the child’s hearing are performed; some tests depend on the age of the child:

• Otoacoustic Emissions (OAEs)—diagnostic DPs and TEs
  
• Tympanometry
  
• Acoustic Reflexes
  
• Unaided audiometric thresholds
  
• Aided audiometric thresholds
  
• ASSR
  
• Auditory Brainstem Response (ABR)
  • Click ( threshold search, and bone conduction)
    
  • Tone Burst (500 Hz & 4000 Hz)
• Speech Perception Testing
  
• MAIS or IT-MAIS ( a questionnaire filled up by parents)

The staff at EARS Inc are highly qualified professionals in the subspecialty of cochlear implantation. Please do not hesitate to call us if you have any questions regarding cochlear implantation.

>> Click here to learn about Cochlear Implant Surgery

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