Résumé
This study is about specific signal generation useful for preoperative electrical stimulation of the cochlea. The proposed generator was intended to check the state of the cochlea's nervous zones of one candidate to cochlear prosthesis apparatus. In fact, this cochlear stimulator would allow the insertion of an electrode into the round window to verify the state of intact nervous zones. Such clinical diagnosis is a useful preoperative evaluation to assure the effectiveness of this apparatus. Originalities in preoperative stimulation techniques of the cochlea were then presented. The overall conceived system included one electronic stage for signal generation dedicated to the stimulation of the nervous zones, as well as a communication software offering to clinicians the control by a graphical module displayed on a host-computer screen. This study was based on a fundamental criterion that was the flexibility and handiness during clinical experimentation. The system for cochlear stimulation was henceforth an electronic apparatus driven by a processor, a 'micro controller', which could be interfaced to the host-computer. The latter displays a graphical module reassembling all the stimulation possibilities around a great flexibility and handiness. In fact, the 'micro controller' used has allowed the generation of different forms of signals for stimulation: thanks to its programming, it was also possible to adjust with great flexibility different parameters such as the stimulation rhythm, the frequency, the amplitude and the stimulation pulses' shape. The signals' shapes proposed here were various: the rectangular shape frequently used, the triangular shape in staircase with different orders and the serrated shape [saw teeth shape] in staircase with different orders. The two latter shapes give multiple forms when varying the order of the staircase evolution. This great variety in the stimulation signals' shape as well as the provided handiness would permit to clinicians better exploration of the cochlea's nervous zones before chirurgical intervention. This would give more information on hearing capacities of patients and on the implant type [one electrode or multi-electrode]