Spectral and Temporal Measures in Hybrid Cochlear Implant Users: On the Mechanism of Electroacoustic Hearing Benefits

Objective Compare auditory performance of Hybrid and standard cochlear implant users with psychoacoustic measures of spectral and temporal sensitivity and correlate with measures of clinical benefit. Study Design Cross-sectional study. Setting Tertiary academic medical center. Patients Hybrid cochlear implant users between 12 and 33 months after implantation. Hybrid recipients had preservation of low-frequency hearing. Interventions Administration of psychoacoustic, music perception, and speech reception in noise tests. Main Outcome Measures Performance on spectral-ripple discrimination, temporal modulation detection, Schroeder-phase discrimination, Clinical Assessment of Music Perception, and speech reception in steady-state noise tests. Results Clinical Assessment of Music Perception pitch performance at 262 Hz was significantly better in Hybrid users compared with standard implant controls. There was a near significant difference on speech reception in steady-state noise. Surprisingly, neither Schroeder-phase discrimination at 2 frequencies nor temporal modulation detection thresholds across a range of frequencies revealed any advantage in Hybrid users. This contrasts with spectral-ripple measures that were significantly better in the Hybrid group. The spectral-ripple advantage was preserved even when using only residual hearing. Conclusion These preliminary data confirm existing data demonstrating that residual low-frequency acoustic hearing is advantageous for pitch perception. Results also suggest that clinical benefits enjoyed by Hybrid recipients are due to improved spectral discrimination provided by the residual hearing. No evidence indicated that residual hearing provided temporal information beyond that provided by electric stimulation.