Author(s)
Ksenia A. Aaron MD
Katelyn E. Glassman, AuD
Mario A. Svirsky, PhD
Matthew B. Fitzgerald, PhD
Affiliation(s)
Abstract:
Objective: To identify how speech understanding is affected by acutely-imposed bilateral mismatches in users of bilateral cochlear implants (CIs). Study design: Repeated measures. Setting: Hospital setting research facility. Patients: 15 sequentially- and 4 simultaneously-implanted recipients of bilateral CIs participated in this study. All had at least six months of bilateral device use at the time of testing. Intervention(s): Bilateral mismatches of insertion depth were simulated by reprogramming one implant. The manipulated ear was either the poorer-performing ear, or the more recently-implanted ear if baseline performance was similar in each ear. The mismatches were simulated by deactivating 2 or 4 electrodes at the apical or basal position, and reprogramming the frequency table. These conditions simulated basalward or apicalward mismatches equivalent to 1.5 or 3 mm. Main outcome measure(s): For each of the four simulated mismatch conditions, CNC word and vowel-identification scores were obtained bilaterally, and for each ear individually. Results: Of the 19 participants, nine showed a significant decrease in speech understanding when an acute bilateral mismatch was imposed. The size of these decrements increased with larger bilateral mismatches. The remaining participants showed no effect of the mismatch. Conclusions: Large bilateral mismatches may hinder performance in some recipients of bilateral CIs. These results are consistent with prior data demonstrating that bilateral benefit is reduced with large bilateral mismatches. However, the observation that bilateral mismatches had no influence on speech understanding in some patients suggests they are adept at monitoring their better ear to avoid interference from the contralateral CI. Define Professional Practice Gap & Educational Needs: In recipients of cochlear implants, bilateral mismatches of insertion depth have long been suggested as a factor that can inhibit performance in these patients. However, very little is known about how patients behave in the presence of such mismatches, particularly with regard to performance on tests of speech understanding with use of clinical speech processors. Learning Objective: To understand how speech understanding is affected when bilateral mismatches of insertion depth are simulated acutely. Desired Result: Participants will understand that many recipients of bilateral cochlear implants may function essentially as a "better-ear" listener when presented with a bilateral mismatch. This can be one reason for the lack of bilateral benefit observed in many recipients of bilateral implants. IRB - Approved