Effect of Interaural Angular Insertion Depth Mismatch on Sound Localization in Adolescent Bilateral Cochlear Implant...

Area of Science:

• Audiology
• Neuroscience
• Biomedical Engineering

Background:

• Adolescents with bilateral cochlear implants (BiCI) since early childhood often exhibit variations in electrode insertion depths.
• Understanding the impact of interaural angular insertion depth (AID) mismatch on auditory perception is crucial for optimizing cochlear implant rehabilitation.

Purpose of the Study:

• To investigate the relationship between interaural AID mismatch and horizontal sound localization accuracy (SLA) in adolescents with long-term BiCI use.
• To determine if varying spatial cues in auditory stimuli influence SLA in the presence of AID mismatch.

Main Methods:

• A cross-sectional study involving 20 adolescents with BiCI, assessed using 3D CT imaging to measure interaural AID mismatch.
• Sound localization accuracy was objectively measured using an Error Index (EI) with four distinct auditory stimuli.
• Statistical analyses included linear regression and group comparisons (matched vs. mismatched AID) based on a 75-degree mismatch criterion.

Main Results:

• A wide range of interaural AID mismatch (median 45.5 degrees) was observed in the BiCI cohort.
• No significant linear correlation was found between interaural AID mismatch and the EI for horizontal SLA.
• While group status (matched vs. mismatched) did not impact overall EI, a significant interaction between stimulus type and group indicated that sound cues affected localization performance in the mismatched group.

Conclusions:

• Significant interaural AID mismatch is common in adolescents with early-onset BiCI, with high inter-individual variability.
• Horizontal SLA appears to be largely independent of the degree of interaural AID mismatch.
• The effectiveness of spatial cues in sound stimuli can influence sound localization performance, particularly in individuals with substantial interaural AID mismatch.