Week 12 Bimodal vs Bilateral Flashcards
what are the benefits of binaural hearing
- binaural auditory squelch= brain focuses on the ear with better SNR
- head shadow effect
- binaural summation
- –the benefits of these are spatial hearing and hearing in noise
when did research show that bimodal stimulation was helping
- early perception of HA fitting on the contralateral ear was unaccepted and thought to potentially cause inference
- by 1990s/ early 2000s this was disproved and it was demonstrated that an improvement in speech recognition and sound localization was had compared to just a monaural CI
how much do bimodal users improve over monaural CI users in terms of word rec
*word and sentence recognition in quiet, and sentence recognition in noise showed mean improvement of 15-20% in bimodal users
is there benefit to those with only functional frequency within a specific frequency range with bimodal stimulation
- yes
- amplification from 0-250Hz in the contra ear improved word and sentence rec in noise for female talkers
- 0-125Hz amplification improved word and sentence rec for male talker
localization in bimodal users
- bimodal users have improvement of localization over CI alone
- it could be affected by the amount of residual hearing in the HA ear or the aided response in the ear
- –symmetrical hearing at low frequency is potentially a good indicator for improved localization
- however, spatial hearing in bimodal users is much poorer than that of normal hearers
- -normal can localize a sound to 1-2 degrees in lover frequency at 0 degrees azimuth
- –bimodal have typically 10 to 60 degree for localization
in what two ways are bimodal recipients localization abilities altered
1) impaired ability to localiza wiht limited inter-aural intensity differences (IID) (>1500 Hz)
- –typically have severe to profound HF HL
2) impaired temporal processing: cant process low frequency temporal cues (<1500 Hz)
- –electric stimulation is poorer than acoustic at this because no phase locking cues
* **this is still better than not being aided at all
what should the HA fit include for bimodal recipients (4 things)
- puretone AC and BC thresholds (octave and inter-octave)
- RECD (real ear-to-coupler difference) Real-Ear probe microphone measures, and REAR–90 (real-ear aided response–90)
- make sure inter-aural loudness balance is achieved while user is wearing both HA and CI
- TEN test to identify dead regions
under what condition do patients with bilateral CI perform better?
- when the signal and noise are spatially separated (speech and noise coming from the same speaker vs from different speakers)
- –CI users are better able to use IID compared to interaural time difference (ITS)
- bilateral CI users have similar benefit of speech recognition in noise compared to bimodal use
amount of improvement in minimum audible angle for bilateral vs unilateral CI
- up to 30 degrees improvement (of localization in noise)
- improvement is most likely due to IID cues
- –bilateral CI users are often (but not always) able to localize better than bimodal users
- —–limited availability of usable inter-aural cues for bimodal users
- —–ITD are difficult to process from bilateral electrical stimulation, however, high frequency IID cues should be available to localize
bimodal vs bilateral (4 points)
- both allow for better speech recognition in noise compared to monaural
- both allow for better localization compared to monaural
- bilateral CI results in better localization than bimodal in most cases
- bimodal stimulation results in better access to pitch and music that cannot be achieved with electrical stimulation
timing of CI surgery for bilateral implants (simultaneous vs sequential)
- simultaneous: both CIs placed in the same surgery
- sequential: both CIs placed, but in two separate surgical procedures
- important considerations:
- –safety: one vs two rounds of anesthesia
- –age: infants have a small blood volume, therefore, simultaneous procedure could raise the risk for blood loss
- –surgeon experience and time of anesthesia
- for children, the outcome of sequential procedures could be affected by the child’s age (both surgeries before 4 years are more successful than after)
- for adults, the outcome of sequential procedures could be affected by the duration of hearing
amplification options with SSD
- CROS
- osseointegrated bone conduction hearing device
- remote mic system
- cochlear implant
- –improved speech in quiet and in noise (when signal and noise coming from the poorer ear
- –improve tinnitus
expectations of CI
- young children should develop some auditory skills and language by the one year mark
- adults (post-lingual) should be able to talk on the phone by 3 months
- if not then we need to start asking the question of why they are not meeting target
8 factors affecting CI outcome
- additional disabilities: low IQ, intellectual disability, autism
- bacterial meningitis: number of electrodes, spiral ganglion damage, neurological effects
- aplastic auditory nerve: absent or deficient nerve
- inner ear malformation: enlarged vestibular aqueduct, inner ear deformity
- pre-lingual vs post-lingual
- duration of deafness
- elderly: cognitive status
- wear time: “eyes open, ears open”
- **of none of these factors, want to look at the device
speech processor checks
- children 3-4 times a year, adults 1-2 times a year
- visual inspection:
- –transmitting cable (children–change every 6 months)
- –batteries/battery contact
- –microphone ports (inspect, listening check, aided sound field – note if mics HF will be affected first)
- internal-external communication
- faulty processor– check backup to see if it is the processor or something else
- if the processor is functioning well
- –check the programming (change thresholds, USL, rate, strategy, etc to see if this helps)
