Cochlear implants Flashcards
Role of Directional Microphone in CI
Ext part 1
Picks up acoustic energy
Changes it to electric signal
Electrical signal sent to speech processor
Role of Speech Processor
Ext part 2
Receives electrical signal from mic
Electrical signal changed to coded signal
Coded signal sent to transmitting coil
Role of Transmitting coil
Ext part 3
Receives coded signal from speech processor
Sends to internal receiver-stimulator
Internal Receiver-Stimulator
Internal Part 1
Receives coded signal from transmitting coil
Sends signal to electrode array
Electrode Array
Internal Part 2
Receives coded signal from internal receiver-stimulator
Stimulates Nerve fibers
Nerve fibers send the msg to the brain
Telecoil and FM battery pack for CI
permit wireless connectivity to telephones, public sound systems, MP3 players & Bluetooth systems
CI are regulated by FDA and are
Class III medical devices
Current youngest age requirement for CI
12 mo. and even younger if candidate
patient selection criteria
requirements that must be met prior to proceeding to implantation
open-set recognition
a response format in which parents write down or repeat test stimuli instea of selecting a response from a group of options (no choices)
Moderate bilateral HL adults can be candidates for CI
Yes- for Cochlear brand.
all candidates must undergo haid trial period before CI
true
hearing aid trial in children can be waived if
there is evidence of cochlear ossification
cochlear ossification
build-up of new bone in response to bacterial meningitis that may have caused an infection in cochlea
HINT-C
was developed as an adaptive procedure to find children’s sentence recognition thresholds or the lowst SNR resulting in 50% recognition
possible physical contraindictions for implantation
- deafness due to lesions in the acoustic nerve or central auditory pathway (such as genetic condition called neurofibromatosis)
- external or middle ear infections, TM performations, Chronic mastoiditis, Cholesteatomas which need to be cleared up before implantation surgery
abnormalities that will render CI useless
Mondini anomaly
EVAS
Mondini anomaly
congenital malformation - Profound SNL HL & a flattened cochlea w/ a single turn
EVAS stands for
Enlarged Vestibular Acqueduct Syndrome
EVAS
the opening in temporal bone is arger than normal & pts present with progressive SNL HL
Useful test for CI
- needle electrode is inserted thru TM & placed on the promontory w/ a surface electrode place on opposite cheek
- good sign if pt experiences the small electrical current (means neurons of aud nerve are stimulable)
Promontory stimulation test
Implant is always placed in “better ear” because
better ear has larger population of surviving nerves in the spiral ganglion to be stimulated (Spiral ganglion sends signals from cochlea to brain)
Mastoidectomy (choice in surgery)
partial or complete removal of the mastoid process & bone
facial recess approach (choice in surgery)
way of surgically accessing the middle ear through mastoid bone through a niche lateral to the facial nerve canal
in CI, surgeon must perform
cochleostomy
Cochleostomy
drilling a hole into the basal turn of the cochlea to insert the electrode array into the Scala Tympani
hook-up
initial delivery & fitting of the CI (external parts)
mapping of CI
initial programming of CI
- the setting of the required electrical stimulation by the cochlear implant for hte pt to hear soft & comfortably loud sounds (goal is to determine dynamic range for each electrode)
- ***The process of setting or adjusting the speech processor based on the dynamic range of each electrode
dynamic range
base on the area b/w electrical threshold level (t-level) and maximum comfort level (C-level)
-difference between t & c level for each electrode
T-level
pt can just detect the sensation of hearing at this level
Speech coding strategies examples
SPEAK
CIS
SPEAK
speech coding strategy that breaks the signal into many (e.g.20) bandpass filters, scans for those having the greatest amplitude, and then conveys teh information via low pulse rates
SPEAK
based on the principle that frequency regions w/ greatest amplitude hav ethe most perceptual salience
CIS stands for
continuous interleaved stimulation
CIS
speech coding strategy estimates the envelope of the acoustic wave by codign the amplitude of the signal in 6 to 8 bandpass filters at a high pulse rate (>800pps)
ACE speech coding strategy
combo of SPEAK & CIS
5 communication options
auditory verbal unisensory oral auditory-oral cued speech total communication ASL/ESL
Definition of auditory verbal unisensory
emphasizes auditory skills
focuses on use of remaining hearing with amplification
no manual communication
*child discouraged from relying on visual cues
Definition of Oral Auditory-Oral
Emphasizes auditory skills AND
stresses use of speechreading*
no manual communication
Definition of Cued Speech
Visual communication system of 8 handshapes (cues) that represent different sounds of speech (makes speech clear through vision)
-allows child to distinguish sounds that look same on lips
Definition of Total Comm
-Philosophy of using every and all means to communicate w/ deaf children…including manual lang based on Eng
definition of ASL
manual language that is distinct from spoken Eng. Eng is taught as 2nd lang
Primary goal of Auditory Verbal Unisensory
To develop speech, primarily thru use of aided hearing alone, & comm skills necessary to integrate into hearing community
Primary goal of Oral auditory-oral
To develop speech & communication skills to integrate into Hearing community
Primary goal of Cued speech
To develop speech & comm skills to integrate into hearing community
Primary goal of Total Comm
to provide an easy, least restrictive communication method b/w deaf child & hearing community
-simultaneous use of manual language and speech is encouraged along with visual & contextual cues
Prim goal of ASL
to be deaf child’s primary lang & to allow child to communicate before learning to speak…prepares child for social access to deaf community
Receptive & exp lang development in auditory verbal unisesnsory
verbal speech developed through amplification
Rec & exp lang development in oral aduitory-oral
combo of amplification & speech reading
Rec & exp lang development in cued speech
use of amplifcation, speech reading, and visual cues of sounds
rec & exp lang development in total comm
Lang (spoken or sign) developed through exposure to oral speech, formal sign language (not ASL), speech reading, & amplification
Auditory verbal vs auditory oral
auditory-oral allows visual cues & speech reading while auditory verbal discourages it
auditory verbal & auditory oral are both appropriate for
young children before age of 2 years (to take full advantage of neural plasticity)
benchmarks
projected performance levels afer CI activation
factors affecting CI benefit
age at time of implantation
quality, type, & amt of auditory experience before implantation
Benchmark-ing
comparing a single patient’s performance to evidence-based, normative outcomes
Red flags
indications that patients are not making avg progress w/ implants
1 Red flag
represents 3 mo. delay in specific skill in auditory progress in children implanted with CI
CHARGE association
variations in temporal bone anatomy found in this disorder make child poor candidate for Ci
-involves colomboma (cleft) of the eye, choanal atreasia (closure) or stenosis (narrowing), cranial nerve abnormalities, outer, middle , and inner ear malformations
Most important determinant of CI outcome in adults
duration of deafness (ex: Postlingually deafened people are already “programmed” for understanding spoken language)
Bimodal stimulation
an arrangement of wearing a haid in the ear opp to cochlear implant
(cochear implant stimulates aud nerve on one side and air-conduction aid provides input to opposite ear)
bimodal stimulation benefits
improved localization & speech recognition performance
bilateral cochlear implants
can be sequential or simultaneous
hybrid cochlear implant
simultaneously provides acoustic input thru a haid for the lower frequencies and electrical stimulation of afferent auditory nerve fibers tuned to the higher frequencies via a cochlear implant to the same ear.
-suitable for people with steeply sloping SNL HL (still have low freq hearing preserved)
Auditory brainstem implant
a hearing prosthesis for pts who have neurofibromatosis, auditory nerve damage from schwannoma removal, or who were born without auditory nerves
schwannomas
turmors that invade the internal auditory canal
Audism
term that describes how the hearing establishment is perceived as imposing their values onto Deaf culture by defining its members as a group of individuals who need treatment
cochlear implant
implantable device designed to substitute for the function of the middle ear, cochlear mechanical motion, and sensory cells (hair cells in inner ear)
Hx of CI
-2 surgeons accidentally stimulated an auditory nerve by electrode placement in a deaf man during an operation for facial nerve repair b& he was able to discriminate some sounds
Hx of CI targeted populations
postlinguistcally deaf adults-> postlinguistically deaf children -> prelinguistcally & congenitally deaf children
2 fundamental modes of stimulation used by CI to send electrical current to auditory nerve
monopolar & bipolar
who performs best with CI
those with residual hearing
Non simultaneous speech coding strategy
CIS-continuous interleaved sampling- uses the full spectrum of the incoming waveform
N of M
SPEAK
n of m strategy
a specified # of electrodes out of the max # are stimulated (only takes the peaks of the signals–the peaks represent formants of the speech)
SPEAK
Spectral Peak Extraction- analyzes the incoming sound to identify filters that have the greatest amt of energy
Simultaneous speech coding strategy
SAS
SAS
simultaneous analog stimulation
simultaneous analog stimulation
the compressed analog waveform is sent simultaneousl to all elctrodes
-hitting all electrodes ate same time has a chance of channel to channel electrode interference
T-level threshold for CI is not the same as hearing threshold level on audiogram
True
RF level
the radio frequency power level required to maintain the proper communication b./w the internal & external components
-set during programming (mapping)
Dual Color LED indicator on CI
LED-light emitting diode *located at top of processor functions are: battery charge status lock status, microphone/ system status (RED=problem)
Ci uses battery as well as audible alarms to alert parents if device is not working
true
Is Aural rehabilitation or Tx required for CI recipients?
Yes, it is KEY factor for success
-for children, it is crucial for development of language & speech skills
Cochlea tonotopic organization
max sensitivity to low frequencies at the apex
max sensitivity to hi frequencies at the base
stimulating electrodes at different regions along teh lenght of the cochlea produces percepts of different frequencies/pitches
true
Channels
filter banks; can be made to correspond to a single electrode (1 to 1 mapping) BUT there is no 1 to 1 mapping between channels & electrodes b/c
1) closely spaced electrodes may not produce diff sound percept
2) # of available electrodes for stimulation depends on mode of stimuation used
monopolar stimulation
1 active electrode & 1 return/ground electrode and current flows b/w the two electrodes
-WIDELY SPACED to stimulate a larger area of neurons
bipolar stimulation mode
2 adjacent electrodes are paired, stimulation is tightly focused on small area of auditory nerve fibers
(2 electrodes only provide 1 channel b/w themselves)
how many electrodes in electrode array
varies, can be 16-24
More is not necessarily better, depends on placement (and can cause more structural damage)
advantage of monopolar mode
can achieve higher loudness levels with lower current (since there is a spread of current over a large # of neurons)
advantage of bipolar mode
stimulation of electrodes in close proximity provides MORE SPATIALLY SELECTIVE STIMULATION
CIs can deliver both bipolar and monopolar modes of stimulation
true
Mode of stimulation is dependent on
Individual needs & responses
Stimulation strategy used (speech coding strategy- that is simultaneous or non-simultatneous)
BP +1 mode
active and reference electrodes separated by one non-active electrode)
-will sound louder than just BP mode because larger neuronal population stimulated
Frequency coding *
depends on rate of nerve firing (temporal theory) & place of stimulation along cochlea (tonotopic./place theory)
Intensity coding *
achieved by manipulation of electrical current pulse width, pusle height, & quantity of auditory nerve fibers stimulated in cochlea
Intensity effects of CI
Once auditory nerve fibers are disconnected from inner hair cells, they no longer have very different response thresholds.
The result of this is that the dynamic range of hearing is very limited in electric hearing.
A limited dynamic range results in poor intensity discrimination and a rapid growth of loudness.
single channel CI
code frequency based on the rate of firing of electrical pulses (temporal theory)
multichannel Ci
uses place theory strategy for coding frequency (different frequencies from the auditory signal are separated and presented in a tonotopic manner alongth length of cochlea via electrode array)
Multichannel CI users experience better speech understanding scores in auditory alone condition vs single channel CI users
true
There is a direct relationship b/w Length of electrode array # of electrodes in array # of channels and mode of stimulation
True
2 purposes of having more electrode sites
provide better frequency resolution (tonotopic)
regions in teh cochlea that respond poorly to electrical stimulation can be avoided during programming
Stimulating “fixed”sites of cochlea -problem
in some cases this fixed location maight not be responsive to electrical stimulation since density & uniformity of neurons in that area vary on etiology of deafness
Simultaneous Analog Stimulation
generates digitally reconstructed analog waveforms & delivers it simultaneously along the electrode sites in the cochlea at high rates
PPS
Paired Pulsatile Sampler
Paired Pulsatile Sampler
an interleaved sampler speech coding strategy hich uses an envelope extraction paradigm called “bin averaging”and
stimulates 2 channels at a time (spaced a few electrodes apart)
Purpose: faster repetition rate can be achieved w/ minimal channel interaction
PPS is
always used in monopolar coupling mode an drquires lesser current levels for stimulation
higher stimulation rates vs stimming neurons with slow rate of pulses
avoids neural synchronicity that would not be normally prsent in auditory system;
improved consonant recognition performance
Outcome prediction Level A
AUDITORY/Verbal Communicator
(3 years post implant, 87% of children predicted to reach this outcome actually reached it)
*Developed awareness of sound few weeks post-implant; sound w/ events by 3 mo, single word use by 1 year, & spken intelligible language by 3 yrs post-implant
Outcome prediction Level B
(BOTH) Auditory verbal/oral communicator w/ visual assist
(after 3 yrs, 85% of children predicted to be in this group actually reached this outcome, while some became A candidates)
-These candidates manifested difficulties that made ADDITONAL THERAPY necessary
(acquired necessary skills such as Candidates A, but just slower)
-ABLE TO ENTER MAINSTREAM EDU
Outcome prediction Level C
COMPLIMENTARY- auditory verbal/oral skills assist a PRIMARILY VISUAL COMMUNICATION
(after 3 yrs, 70% predicted to be in this group maintained performance -peaked at a key word acquisition stage & could use stereotypical phrases, but none become A candidates)
*achieved awareness of sounds at 4 months, developed associaton of sounds w/ evens within 6-15 mo, devceloped single word use around 24 mo., developed understanding & emerging phrases around 3 yrs then plateued.
-THESE CANDIDATES BENEFIT BEST FROM ASL as primary mode of comm
Outcome Predication level D
DOESNT benefit from implant
