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Quantitative Assessment of Cortical Auditory-tactile Processing in Children with Disabilities
Published on: January 29, 2014
Abnormal timing delays in auditory brainstem responses evoked by bilateral cochlear implant use in children
Karen A Gordon1, Jerome Valero, Richard van Hoesel
1Cochlear Implant Laboratory, The Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada. karen.gordon@utoronto.ca
Insights
A long delay before bilateral cochlear implants disrupts auditory brainstem timing. This disruption persists for at least nine months after receiving the second implant, impacting binaural processing.
Area of Science:
- Auditory neuroscience
- Neurophysiology
- Cochlear implant technology
Background:
- Unilateral cochlear implant use can decrease electrically evoked auditory brainstem response (EABR) latencies.
- This latency change may interfere with binaural timing cues crucial for processing bilateral auditory input.
Purpose of the Study:
- To investigate the impact of delayed sequential bilateral cochlear implantation on auditory brainstem processing timing.
- To assess how the duration of unilateral implant use affects the development of binaural auditory function.
Main Methods:
- Electrically evoked auditory brainstem responses (EABRs) were recorded in children implanted sequentially with a long delay (>2 yr), short delay (<1 yr), or no delay.
- Responses were measured using left, right, and simultaneous bilateral stimulation at initial fitting, 3 months, and 9 months post-bilateral implantation.
Main Results:
- The non-implanted (naive) ear exhibited prolonged EABR latencies compared to the experienced ear.
- Latency prolongation diminished over time in both short and long delay groups, but remained significant in the long delay group.
- No significant latency differences were observed between left and right implants in simultaneously implanted children.
Conclusions:
- A significant delay (>2 years) between unilateral and bilateral cochlear implantation can disrupt binaural brainstem processing timing.
- These timing disruptions persist for at least nine months after the second implant is activated.
- Findings highlight the importance of timely bilateral cochlear implantation for optimal auditory development.
Hypothesis:
A period of unilateral implant use before bilateral implantation affects timing of brainstem processes measured by the electrically evoked auditory brainstem response (EABR).
Background:
EABR latencies decrease with unilateral implant use potentially disrupting binaural timing cues important in auditory brainstem processing of bilateral input.
Methods:
EABRs were evoked by electrical pulses from the left, right, and both implants simultaneously in 3 groups of children. All were initially implanted at ages younger than 3 years and had the following: 1) a long delay (>2 yr [n = 16]), 2) a short delay (<1 yr [n = 15]), or 3) no delay (n = 15) between left and right ear implantation. Responses were recorded on the first day of bilateral implant use and 3 and 9 months thereafter.
Results:
Relative to responses evoked in the experienced ear, the naive ear showed prolonged latency in both the EABR peaks and the binaural difference response. After 3 and 9 months of bilateral implant use, the relative prolongation decreased in the long and short delay groups, but significant differences persisted in the former. No clear differences in latencies evoked by the left versus right implant were found at any time point in children receiving bilateral implants simultaneously.
Conclusion:
Results suggest potential disruptions to binaural brainstem processing based on timing cues in children receiving a second cochlear implant after more than 2 years of unilateral implant use that persist through at least the first 9 months of bilateral implant use.
