Results and perspectives with extracochlear round window electrodes.

The results obtained with implanted electrodes at the round window are comparable to results with electrodes in the scala tympani or in the hearing nerve in respect to frequency and amplitude resolution with pulsatile and sinusoidal stimulation (with considerable interpatient variations). Although the subjective quality of the perceived sounds is expected to vary depending on the stimulation site, it seems that timing effects of electrical stimulation may play a major role in pitch perception as required for voice and sound recognition or prosody identification. Our technique is a safe procedure involving only routine middle ear surgery to place the induction coil within the mastoid bone and to put an electrode at the round window margin. By an external stimulator, sounds are transformed to electrical stimuli suited to excite surviving fibers of the cochlear nerve. This helps the patient to communicate and provides some basic cues for speech discrimination.