ShortTerm Auditory Stimulation through Contralateral Hearing Aid Use in Pediatric Cochlear Implant U

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Short-Term Auditory Stimulation through
Contralateral Hearing Aid Use in Pediatric
Cochlear Implant Users

• Kelly Clingempeel Skubisz, Ph.D.
• Brenda C. Seal, Ph.D.
• Lincoln Gray, Ph.D.
• James Madison University
• Harrisonburg, Virginia

ASHA Convention Miami, FL November 16, 2006
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Background

• Binaural hearing Essential to the accurate
  perception of stimuli, particularly in background
  noise, and is necessary for localization
• Unilateral implantation
• The current standard for cochlear implant
  recipients
• Amplification in the nonimplanted ear
• Few choose or are given the option
• Binaural benefit could be demonstrated
• Amplifying residual hearing in the nonimplanted
  ear
• Negative effects of auditory deprivation
• Effects of leaving the contralateral ear without
  amplification may or may not be confined to a
  critical period

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Neural Plasticity

• James Willot (1996) Hearing aid use can take
  advantage of the plasticity in the system and
  potentially restore auditory function and cause
  reorganization of the central auditory system.
• Karen Gordon, Blake Papsin, and Robert Harrison
  (2003) ECAPs and EABRs were obtained in the
  majority of children with cochlear implants, upon
  initial stimulation with the implant.

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Plasticity and Critical Periods

• Sininger, Doyle, and Moore (1999)
• Sharma, Dorman, Spahr, and Todd (2002)
• A critical time period exists when auditory
  stimulation must occur in order to take advantage
  of the plasticity of the nervous system
• Gordon, Papsin, Harrison (2003)
• Ponton, Don, Eggermont, Waring, Kwong, and Masuda
  (1996)
• Although a critical period may exist,
  development can occur after that point.

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Hearing Aids and Cochlear Implants Adult Studies

• Cohen, and Shapiro,1992
• Armstrong, Pegg, James, and Blamey,1997
• Tyler, Parkinson, Wilson, Witt, Preece, and
  Noble, 2002
• Ching, Incerti, and Hill, 2004
• Iwaki, Matsushiro, Mah, Sato, Yasuoka, Yamamoto,
  and Kubo, 2004
• Seeber, Baumann, and Fastl, 2004
• Flynn and Schmidtke, 2004
• Kileny, Snorrason, Zwolan, Macpherson, and
  Middlebrooks, 2004
• Morera, Manrique, Ramos, Garcia-Ibanez, Cavalle,
  Huarte, Castillo, and Estrada, 2005
• Kong, Stickney, and Zeng, 2005
• All showed binaural advantage (localization
  and/or speech in noise)

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Hearing Aids and Cochlear Implants Children
Studies

• Studies that showed binaural advantage
• Chmiel, Clark, Jerger, Jenkins, and Freeman
  (1995)
• Ching, Psarros, Hill, Dillon, and Incerti (2001)
• Dettman, DCosta, Dowell, Winton, Hill, and
  Williams (2004)
• Holt, Kirk, Eisenberg, Martinez, and Campbell
  (2005)
• Studies that did not show binaural advantage
• Waltzman, Cohen, Shapiro, 1992
• Godar, Litovsky, Johnstone, and Agrawal, 2004

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Research Questions

• Do localization and speech discrimination in
  noise improve when children with cochlear
  implants wear a hearing aid in the contralateral
  ear for a short period of time?
• Does the length of time the contralateral ear has
  been without stimulation affect performance with
  the hearing aid?
• Can measures of localization and speech
  discrimination obtained during testing be
  correlated with each other or with subject
  demographics?

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Subjects

• 6 prelingually-deaf children, ages 5-7½, with
  bilateral severe-to-profound hearing loss
• Obtained through JMU Sign Language Research
  Laboratory and the Cochlear Implant Educational
  Center at the Laurent Clerc National Deaf
  Education Center at Gallaudet University
• Consistent users of Cochlear Nucleus implant
  system with stable MAPs
• No prior consistent hearing aid use with their
  implant

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Subjects
Mean and SD thresholds in the non-implanted ears
of the 6 subjects. All in severe to profound
range.
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Subject Demographics
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Procedures

• Parental consent forms obtained and CI
  questionnaire completed.
• Initial testing CI alone or CIHA (randomized).
• Contralateral HA was then fit on the child or
  taken off.
• At least 30 min. of intense listening with the CI
  and HA preceded testing with HA.
• Repeat testing CI alone or CIHA.
• All testing occurred twice with no less than 2
  weeks between sessions.
• Over the 2 test sessions, each child was tested
  either first with CI alone and then with CIHA or
  first with CIHA and then CI alone.

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Testing Protocol

• Speech Perception
• Early Speech Perception (ESP) test (Moog Geers,
  199018) assesses perception of patterns,
  spondees, and monosyllables using picture cards
• Stimuli presented in soundfield at 45 to the L
  and R of the participant at a S/N ratio of 10 dB
  in 2 conditions
• Speech on implant side, noise on HA side
• Noise on implant side, speech on HA side
• Speech at 65dB A noise at 55dB A
• 12 words randomly chosen for each aided condition
  for pattern, spondee, and monosyllable perception
  and for noise condition
• Localization
• FM tone at 1000 Hz in soundfield from
  loudspeakers at 45 to the L and R of participant
  at 70 dB SPL
• 20 presentations for each aided condition
  randomized before testing
• Localization sessions videotaped and viewed by 2
  impartial parties (98.8 agreement between these
  viewers and investigator)

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Effect of Hearing Aid

• Noise on CI side
• Pattern perception t(5) -1.585,
• p .05
• Spondee perceptiont(5)
• -3.079, p
• Monosyllable perceptiont(5)
• -3.208, p
• Noise on HA side
• Pattern perception t(5) -2.483,
• p .05
• Spondee perception t(5)
• -1.535, p .05
• Monosyllable perception t(5)
• -.355, p .05

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Effect of Hearing Aid Individual Performances
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Effect of Hearing Aid for Localization

• No main effect of hearing aid F(1,5) 2.626, p
  .05
• Post-hoc paired t-tests
• Localization performance was significantly better
  in the CIHA condition for trial 1 t(5)
  -3.005,
• p
• -.456, p .05.

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Effect of Hearing Aid for Localization
Individual Performances
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Correlations between PC Scores and Subject
Demographics

• No significant correlation between chronological
  age, age at implantation, length of implant
  experience, pure tone average and any scores from
  the speech perception and localization tests.
• No significant correlation between speech
  perception and localization scores.
• Significant correlation between length of prior
  HA experience and pattern perception, spondee
  perception, and monosyllable perception.
• No significant correlation between length of
  prior hearing aid experience and localization.

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Effect of Trial

• Essentially no difference in performance on ESP
  test between trials - suggests negligible effects
  of fatigue and learning on speech perception
  measures.
• Localization ability with the implant alone
  improves as the subject becomes more familiar
  with the task suggests that localization may
  require learning and improve with experience
  and/or training.

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Effect of Noise

• Average binaural benefit was greatest across all
  ESP subtests when the noise was on the implant
  side versus the hearing aid side. This finding
  is in agreement with results obtained in previous
  studies.
• Suggests that the hearing aid contributes
  successfully to the integration of the speech and
  noise signals, even after a short period of
  bimodal stimulation.

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Effect of Hearing Aid

• Average scores were significantly higher on the
  spondee and monosyllable perception tests in the
  CIHA condition versus the CI alone condition
  with noise on CI side.
• Although scores were higher in the CIHA
  condition on pattern perception, they did not
  reach a level of significance.
• This may have been due to ceiling effects with
  many subjects scoring 100 during this condition.
  
• No significant effect of hearing aid when noise
  was on HA side.
• Less overall benefit in this noise condition.

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Effect of Hearing Aid

• All participants demonstrated binaural benefit
  for at least one ESP subtest.
• One subject showed no binaural benefit on any ESP
  subtest with noise on CI side.
• One of later-implanted children in the study
• 8 months of implant experience.
• Most residual hearing in the nonimplanted ear,
  but was not fit with HAs until 1½ years of age
  and was fit with frequency-compression hearing
  aids.
• Several instances of decreased PC scores in the
  CIHA condition.
• Majority of these cases, the decrease in
  performance was not considered clinically
  significant (
• One subject scored more than 20 worse on the
  monosyllable perception test when the noise was
  presented from the HA side
• Wore hearing aids for the shortest length of time
  prior to receiving the cochlear implant.
• Demonstrated the most binaural benefit on the
  pattern perception test among all 6 subjects for
  this noise condition.

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Effect of Hearing Aid - Localization

• Most participants did show improvement in PC
  scores, although binaural benefit did not reach
  the level of significance when both trials were
  considered.
• Some of these children were able to use the
  information provided from the hearing aid and
  adjust to the addition of stimulation. We
  interpreted this to suggest their auditory system
  is still relatively plastic.

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Clinical Implications Speech Perception

• Even after short-term contralateral hearing aid
  use, the children in this study performed
  similarly to children in other studies who had
  more experience in the bimodal condition.
• When considering the difficulty of a speech
  perception task, the importance of the
  contralateral hearing aid is increased when
  competing noise is present.
• Short-term bimodal amplification may be useful
  for speech therapy or auditory training sessions
  or in classroom learning settings where
  background noise is an issue.
• Significant, positive correlation between percent
  correct scores for speech recognition and length
  of HA use prior to implantation.
• Children who had limited hearing aid experience
  before receiving a cochlear implant may not
  perform as well as those children who wore
  hearing aids for an extended period of time.

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Clinical Implications - Localization

• Binaural benefit did not reach statistical
  significance when considering both trials.
• May be due to critical periods of auditory
  development. There is research to suggest that
  only limited auditory development occurs after 5
  years of age, at least as far as sound
  localization is concerned. The children in this
  study were all over the age of 5, average age of
  56.
• Studies have shown binaural benefit for
  localization in children who wear a cochlear
  implant and hearing aid, and it may be the
  short-term auditory stimulation with the
  contralateral hearing aid supplied in this study
  did not allow for development of auditory
  pathways responsible for accurate sound
  localization.

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Clinical Implications Critical Periods and
Plasticity

• There are researchers who suggest no critical
  period while others argue the critical period is
  limited to the first 5 years of a childs life
  and depends on auditory stimulation.
• Results of this investigation suggest that the
  auditory system of 5-year-old implanted children
  can immediately integrate acoustical information
  from the hearing aid with the electrical
  information from the implant.
• These results further suggest that the auditory
  system does not require reorganization, and
  particularly for children whose early hearing aid
  use could have promoted pathways for auditory
  stimulation.
• This study suggests that auditory plasticity is
  maintained or available at least until 7½ years
  of age, the age of the oldest participant.
• These results do not challenge theories of a
  critical period when auditory stimulation,
  specifically acoustical stimulation, must occur,
  but they do challenge the age and duration of
  stimulation needed to define a critical period.

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Limitations

• The small number of subjects makes
  generalizations about all pediatric cochlear
  implant users difficult (future research with
  higher n?)
• The binaural benefit seen in this study may not
  apply to newly-implanted children or children who
  fall outside the age range included in this study
  or who were implanted beyond 5 years old.
• Speech perception test used for this study was a
  closed-set picture test
• More difficult speech recognition tests (i.e.
  open-set word recognition tests) may require
  prolonged hearing aid use in the nonimplanted ear
  in order to observe binaural benefit (more
  research?)
• Stimulus for localization test
• ITDs become imperceptible above 1500 Hz, and IIDs
  become less distinct at frequencies around 1000
  Hz and below.
• It is possible that either a higher or lower
  frequency tone or noise burst would have been
  easier to localize and have been more sensitive
  to binaural benefit provided by the addition of
  the contralateral hearing aid.

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Summary

• Speech discrimination in noise did improve when
  children with cochlear implants wore a hearing
  aid in the contralateral ear for a short period
  of time.
• Localization did not significantly improve in the
  bimodal condition for these children.
• Length of time the contralateral ear has been
  without stimulation could not be significantly
  correlated with performance in the bimodal
  condition.
• Localization and speech discrimination results
  obtained during testing could not be
  significantly correlated with each other,
  however, speech recognition performance was
  significantly correlated to length of prior HA
  experience.

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Conclusion

• The present findings not only increase our
  understanding of the combined benefits of
  cochlear implants and hearing aids, auditory
  plasticity, and critical periods, but enlighten
  theories of auditory plasticity, critical
  periods, and the ability of the auditory system
  to integrate different signals from both ears.

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Gratitude is extended to

• Debra Nussbaum, Susanne Scott, and everyone at
  the Cochlear Implant Education Center at
  Gallaudet University and JMU Speech and Hearing
  Lab who helped me find and test all the children.
• The families of the children who worked with me
  in order to have their child participate in this
  study.
• My mom and dad who watched hours of localization
  testing for reliability.