Plinkert P K, Baumann J W, Lenarz T, Keiner S, Leysieffer H, Zenner H P
Universitätsklinik für Hals-Nasen-Ohrenheilkunde, Tübingen.
HNO. 1997 Oct;45(10):828-39. doi: 10.1007/s001060050161.
Recently, we presented an implantable piezoelectrical hearing aid transducer. Its characteristics make it suitable for implantation in patients with sensorineural hearing loss. The transducer transmits micromechanical vibrations instead of sound into the hearing organ. Efficiency of the transducer implant was investigated in ten cat ears. After determining preoperative (acoustical) BERA threshold, the middle ear was opened and the piezoelectrical transducer coupled to various ossicles or the perilymph. BERA responses were recorded following stimulation of umbo, long incus process, stapes head, stapes foot plate, and vestibulum. By comparing the acoustical and mechanical threshold, a correlation was found between the stimulus level of acoustical and mechanical stimulation. An electrical transducer voltage of 1 Vrms was equivalent to sound-pressure levels between 100 and 128 dB SPL at the tympanic membrane. To judge hearing impression, stimulus-dependent latencies of the early acoustically and mechanically evoked potentials (waves P1 to P5) and their thresholds were analyzed. After coupling the piezoelectrical transducer to the long incus process, latencies corresponded well to stimulation. They were almost completely similar when the equivalent sound-pressure level of 100 dB SPL was achieved by the transducer voltage level.
