Hybrid Cochlear Implant Helps Preserve Residual Low-Frequency Hearing

How well does acoustic plus electric processing work for those implanted with a new cochlear implant type, and how does it compare to electric-only processing?

Background: Cochlear implants (CI) have been highly successful in restoring hearing in individuals with postlingual deafness and in children who are prelingually deafened and implanted early. Until recently, those with residual hearing, usually in the low-frequency (LF) apical region of the cochlea, have not been candidates for standard CIs because implantation destroys most useful remaining hearing. A CI that could provide stimulation to the damaged high-frequency regions of the cochlea while preserving LF hearing offers numerous advantages.

Study design: Multicenter, longitudinal, single-subject FDA trial with 87 subjects who received a Nucleus Hybrid S8 CI in their poorer ear, running from 2002 to 2011 and involving 19 surgeons across 17 U.S. centers.

Setting: Arizona Ear Center, Phoenix; California Ear Institute, Palo Alto; Center for Hearing & Balance; Dallas Otolaryngology Associates, Dallas; Denver Ear Associates, Englewood, Colo.; House Ear Institute, Los Angeles; Indiana University School of Medicine, Indianapolis; Mayo Clinic, Rochester, Minn.; Michigan Ear Institute, Farmington Hills; Midwest Ear Institute, Indianapolis; New York University Cochlear Implant Center; University of California San Francisco; University of Florida, Gainesville; University of Iowa, Iowa City; University of Miami, Coral Gables, Fla.; University of Washington, Seattle; UT Southwestern Medical School, Dallas.

Synopsis: Surgical implantation of a 10-mm electrode in the scala tympani resulted in hearing preservation in nearly all subjects; only 1.3% experienced total hearing loss within one month following implantation. Individual threshold evaluation at initial activation showed that 94% maintained functional hearing from 125 to 500 Hz. Significant improvements were seen in 82.5% in the hybrid condition, 87.5% in the combined condition, and 60% in the electric-only condition. In both the hybrid and combined conditions, 55% had improvements in speech understanding in noise. Age at implantation was a significant predictor of the consonant-vowel nucleus-consonant (CNC) score in the hybrid condition but not in the combined condition. The longer the duration of deafness, the lower the CNC score at 12 months post-implantation. A history of noise exposure and male gender had a negative impact on performance with the implant. Fourteen individuals requested that the Hybrid S8 implant be removed due to dissatisfaction with the device. Only a few of these subjects performed significantly better with the standard CI implant. Study limitations included a lack of complete follow-up for some patients and variability in performance.