Cochlear Implantation Improves Hearing in the Contralateral Ear

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Abstract
The electrical stimulation of deaf ears by cochlear implants (CI) improved contralateral hearing in seven patients: 5 intracochlear (IC) (analogue processor) and 2 extracochlear (EC) (digital processor) implants. Our patients obtained best speech discrimination scores (98% + 2%, n = 11) when lip reading and CI were combined with a high-power hearing aid fitted into the contralateral ear. Contralateral hearing improvement was 10-15 dB sound pressure level (SPL) at frequencies up to 4000 Hz; hearing in a previously totally deaf ear recovered 4-6 months after CI. The phenomenon was independent of the type of speech-encoding (analogue or digital). Five out of 6 reimplanted patients who first received an 8-channel digital-pulsatile EC reported better speech discrimination after the second CI, when IC devices were implanted with analogue speech processors. These results suggest that EC implantation should be considered in childhood as a first choice, since i) It does not exclude the possibility of a second IC implantation with the same success rate as for the first; ii) The inner ear sensory epithelium remains intact after EC implantation, and consequently, if any regenerating process takes place in the implanted ear due to electrical stimulation it may provide more physiological hearing later on.