Transcript Cochlear Implant

Cochlear Implants
Jeffrey R. Scott, Ph.D.
Ear Anatomy
Hearing Physiology
Hearing Physiology
For a low frequency sound, the traveling wave peaks
near the apex of the cochlea; for a mid-frequency
sound, the peak is near the middle, and for a high
frequency sound, the peak is near the base of
the cochlea.
Hearing Physiology
Ear Function – Video
03:25
Deafness – Definition
Deafness
The lack or severe impairment of the sense of hearing.
Deafness – Scope
-Approximately 17 percent (36 million) of American adults report some degree of hearing loss.
- There is a strong relationship between age and reported hearing loss:
18 percent of American adults 45-64 years old
30 percent of adults 65-74 years old
47 percent of adults 75 years old or older have a hearing loss.
- Of adults ages 65 and older in the United States, 12.3 percent of men and nearly 14 percent of
women are affected by tinnitus (ringing in the ears).
- 15 percent (26 million) of Americans between the ages of 20 and 69 have high frequency
hearing loss due to exposure to loud sounds or noise at work or in leisure activities.
Children:
- 2-3 out of every 1,000 children in the United States are born deaf or hard-of-hearing.
Deafness - Types
Conductive Hearing Loss
Conductive hearing loss occurs when sound is not conducted efficiently
through the outer ear canal to the eardrum and the tiny bones (ossicles) of the
middle ear. Conductive hearing loss usually involves a reduction in sound
level or the ability to hear faint sounds.
Sensori-Neural Hearing Loss
Sensori-Neural (or "nerve" hearing loss) results from damage to the hair cells,
nerve fibers or both in the inner ear. This is the most common type of hearing
loss and is often caused by aging or prolonged exposure to noise. It also can be
caused by high fever, birth defects and certain drugs. People with sensorineural hearing loss can hear speech, but frequently have difficulty
understanding it. The problem is usually compounded when background
noise is present.
Neural – Hair Cell Damage
- Illnesses
- Drugs that are toxic to hearing
- Hearing loss that runs in the
family (genetic or hereditary)
- Aging
- Head trauma
- Malformation of the inner ear
- Exposure to loud noise
Neural – Hair Cell Damage
Before and After Loud Sounds - The top
electron microscope photo shows the tiny
hair bundle on top of a healthy inner ear
hair cell. Compare it to the bottom electron
microscope photo of a sound-damaged
hair bundle again on top of an inner ear
hair cell.
Deafness - Causes
Hereditary disorders - some types of deafness are hereditary, which means parents pass
on flawed genes to their children. In most cases, hereditary deafness is caused by
malformations of the inner ear.
Genetic disorders - genetic mutations may happen: for example, at the moment of
conception when the father’s sperm joins with the mother’s egg. Some of the many genetic
disorders that can cause deafness include osteogenesis imperfecta, Trisomy 13 S and
multiple lentigines syndrome.
Prenatal exposure to disease - a baby will be born deaf or with hearing problems if they
are exposed to certain diseases in utero, including rubella (German measles), influenza
and mumps. Other factors that are thought to cause congenital deafness include exposure
to methyl mercury and drugs such as quinine.
Noise - loud noises (such as gun shots, firecrackers, explosions and rock concerts),
particularly prolonged exposure either in the workplace or recreationally, can damage the
delicate mechanisms inside the ear.
Trauma - such as perforation of the eardrum, fractured skull or changes in air pressure
(barotrauma).
Disease - certain diseases can cause deafness, including meningitis, mumps,
cytomegalovirus and chicken pox. A severe case of jaundice is also known to cause
deafness.
Deafness - Causes
Age-related hearing loss
Hearing gradually becomes less acute as we age. This is normal, and rarely leads to
deafness. Age-related hearing loss (presbycusis) typically begins with the loss of higher
frequencies, so that certain speech sounds - such as ‘s’, ‘f’ and ‘t’ - end up sounding very
similar. This means the older person can hear, but not always understand.
Tinnitus is often associated with deafness
Tinnitus means a sensation of ringing in the ears. Some of the causes of tinnitus include
middle ear infections and damage to the ear from loud noises. Tinnitus may occur on its
own, or in conjunction with hearing loss.
Deafness – Diagnostic Tests
Air Conduction, Conventional or Standard Audiometry
This test is commonly used to measure the hearing of adults and
older children. A range of test tones, from low to high frequency
(perceived as "pitch"), is transmitted through earphones placed on
or in each ear, and patients are asked to indicate with a hand raise,
button push or verbal response when you hear each sound. This
testing determines the very softest signals you can hear at each of
the presented frequencies, and indicates frequency regions in
which hearing may be impaired. The louder the sounds must be
made to be heard, the greater the degree of hearing loss at that
particular frequency or frequencies. The frequencies tested are
those important for hearing and understanding speech and other
environmental sounds.
Bone Conduction
If testing reveals a hearing loss, another type of headset, a bone
vibrator, is used to determine hearing by bone conduction in order
to determine the type of hearing loss. This device sends sounds
directly to the inner ear, bypassing the outer and middle ear. If the
sounds are heard better by bone conduction, the hearing loss is
conductive in nature and is likely located in the outer or middle
ear. If the sounds are heard equally well with the earphones and
the bone vibrator, the hearing loss is sensorineural in nature. A
combination of conductive and sensorineural hearing loss also may
be present; this is called a mixed hearing loss.
Deafness – Diagnostic Tests
Word Recognition
In addition to tests with tones, word recognition testing is usually performed to evaluate the
ability to discriminate differences between the speech sounds of various words, and how clearly
the words are heard. During this test, you will be asked to listen to and repeat words.
Acoustic Immittance
These tests are used to assess the status of the middle ear and related structures. A type of
acoustic immittance test called, tympanometry, measures the movement of the eardrum to see if
it moves normally when pressure changes are applied. Restricted eardrum movement could
indicate a problem with the eardrum or middle ear structures. Acoustic reflex testing, a method
of determining how the middle ear reacts to loud sounds also might be tested.
Otoacoustic Emissions (OAEs)
OAEs are used to assess the function of the cochlea. OAEs are typically present when hearing is
normal or near normal, and are typically absent when there is a problem in the cochlea.
Auditory Brainstem Response (ABR)
ABR is a procedure used to measure hearing sensitivity and determine if the neural pathways
within the brainstem are transmitting sound properly. This test is used to rule out auditoryneurological problems. Brainwave activity in the auditory centers of the brain is recorded in
response to a series of clicks or tones presented to each ear. During this procedure, electrodes are
placed on the head to detect the electrical response of the brains to sounds presented while you
rest or sleep. The electrodes do not cause pain or discomfort.
Hearing Aids
Amplification Only
Indications for a Cochlear Implant
- Adult
- 18 years old and older (no limitation by age)
- Bilateral severe-to-profound sensorineural hearing
loss
- Psychologically suitable
- No anatomic contraindications
- Medically not contraindicated
Indications for a Cochlear Implant
- Child
- 12 months or older
- Bilateral severe-to-profound sensorineural hearing loss
- No appreciable benefit with hearing aids (parent survey when <5 yo
or 30% or less on sentence recognition when >5 yo)
- Must be able to tolerate wearing hearing aids and show some aided
ability
- Enrolled in aural/oral education program
- No medical or anatomic contraindications
- Motivated parents
Structure of a Cochlear Implant
Microphone
Amplification
External speech processor
Compression
Filtering
Shaping
Transmitter (outer coil)
Receiver
Electrode array
Neural pathways
Cochlear Implant
Approximately 188,000 people worldwide
have received cochlear implants. In the
United States, roughly 41,500 adults and
25,500 children have received them.
What is a Cochlear Implant? - Video
01:55
Cochlear Implantation XRay - Video
01:11
How does a Cochlear Implant Work?
How does a Cochlear Implant Work?
- Video
02:10
Activation - Video
02:50
Cochlear Implants
Jeffrey R. Scott, Ph.D.