Studying the history of auditory implantation and following the developments that have taken place in only some 50 years is exciting and teaches us about the courage, vision, and endurance of some special individuals in and from different parts of the globe. It also makes us realize that the cochlear implant (CI) has been developed through multidisciplinary efforts and would not have existed if other developments had not paved the way; for example, without the experience with silicone-covered leads in pacemakers, biocompatibility studies, and the existence of antibiotics, this development would not have been possible. The reactions of disbelief and skepticism in the community of auditory professionals, and later the reactions of anxiety and anger in the deaf community to these new developments—which felt like a threat and an offense to their culture and way of living—also demonstrate the sociological impact that the cochlear implant has had and sometimes still has. Finally, this chain of development could not have taken place without serendipity lending a hand, and without some very courageous patients who decided in close consultation with their doctors to become objects of research for this possible new treatment.

Some other experiments involving electrical stimulation of the auditory system were described in those years, all without tonal quality of sound. In 1855 Duchenne of Boulogne (1806–1875), based in Paris, stimulated the ear with alternating current instead of direct current, leading to a sensation of “the beating of a fly’s wings”; still an unsatisfactory outcome.

In the 1930s Stanley Smith Stevens and his colleagues described “electrophonic hearing,” thought to be the mechanism by which cochlear structures respond to electrical stimulation to produce hearing and therefore only present in intact cochleae. It is now known that electrophonic hearing is a result of the mechanical oscillation of the basilar membrane responding to voltage changes. Before 1957, efforts to stimulate hearing electrically were performed on patients with at least a partially functioning cochlea. The results therefore could have been based on electro-phonic hearing instead of on direct stimulation of the auditory nerve. The early pioneers had to prove the effect of their auditory implant as being a result of stimulation of the auditory nerve and not electrophonic hearing.

Andre Djourno and Charles Eyries (1957)

The first direct electrical stimulation of the auditory nerve was performed in the 1950s by the French-Algerian surgeons Andre Djourno (1904–1996) and Charles Eyries (1908–1996). They each had a different interest and background. Whereas Djourno was a scientist who had studied medicine, and had been interested in medical applications of electricity and nerve stimulation for a long time, Eyries was a trained otolaryngologist and was more of a clinician. He had more interest in the facial nerve embryology and function and ways to restore this function.

Before they worked together, Djourno had already produced a device to continuously measure pulse, had used electroencephalogram to study narcolepsy, and had originated the use of electricity for removal of metal pieces from bones. He also invented some sort of artificial respiration by direct stimulation of the phrenic nerve. With these inventions he showed his deep interest in neural stimulation by the use of prostheses. His next project of interest was the making and testing of “implantable induction coils” (which he called “microbobinages”). He made these coils himself to use for “telestimulation,” and tested them in rabbits. The induction coil was placed under the skin and the stimulation was delivered transcutaneously. Subsequently, the rabbit jumped after stimulation of the sciatic nerve. He studied several aspects of telestimulation, among which were electrode biocompatibility, the effect of long-term telestimulation of a nerve, and the effect of stimulus frequency. Because with higher frequency the muscle did not contract and with lower frequency the contraction was painful, he determined that the ideal stimulus frequency was around 450 Hz, finally using his own voice as the telestimulus because it was of the appropriate frequency. This finding might have prepared him for the idea of stimulating the auditory nerve to restore hearing.

A 57-year-old male patient, who presented postoperatively with both bilateral loss of hearing and bilateral loss of facial mobility after bilateral resection of large cholesteatomas, brought Djourno and Eyries together. In the quest for a possible nerve graft, Eyries met Djourno at the laboratories of the medical school in Paris and they decided together with the patient on a surgical procedure with the purpose of restoring facial as well as acoustic nerve function.

This procedure was performed on February 25, 1957, by Eyries, during which the induction coil was placed under the temporal muscle and the active electrode was placed in the stump of the auditory nerve, while at the same time the facial nerve graft was applied. The procedure restored facial nerve function by the graft. The reports on the auditory outcome, also partly tested intraoperatively, showed encouraging responses. After extensive rehabilitation with a speech therapist, auditory sensations were present; discrimination between lower and higher frequencies was detected, but there was no speech perception. Unfortunately, after some weeks the implanted electrode broke down, and a subsequently implanted second device also broke down. Eyries held Djourno responsible for the breakdown of the electrodes and refused to perform a third implantation; this marked the end of their working partnership and communication.

Djourno, however, went on and was approached by a colleague who proposed to organize funding and engineering support for further development of the implant in collaboration with industry, in exchange for exclusivity. A true academician, Djourno refused; he was not interested in profiting from his inventions and detested industry. Out of principle he implanted one more patient together with a different, third surgeon. This implantation was not successful and because of lack of funding Djourno finally stopped working in the field of auditory prostheses.

The activities of Djourno and Eyries were followed up in Paris by Claude-Henri Chouard, a student in Eyries’s laboratory. He became instrumental in the development of one of the first functional multichannel implants, the Chorimac-12 (now Neurelec/MXM-Oticon). He considered Charles Eyries as his major source of inspiration. Because of the work and implantation of Djourno and Eyries in 1957, that is seen as the year in which the development of auditory implants started.

The discoveries of Djourno and Eyries did not reach the outside world or the United States quickly: they published their findings in a French medical journal and the connections of Djourno, the scientist rather than the surgeon, with American otolaryngologists were not close. Eyries, the clinician, on the other hand did not show much enthusiasm for the project and that only briefly. William House in California serendipitously was given a translated English summary of the French manuscript via a patient around 1959. The manuscript was very positive on the findings and House became inspired.