[Use of a body acoustic probe and the conduction of brain stem potentials for the determination of sound conduction during tympanoplasty].
A new procedure of evoking brain stem potentials is introduced. Contrary to evoking brain stem potentials by acoustic stimulation via earphone or loudspeaker, we touch the middle ear apparatus at various locations using a piezoelectric transducer with a screwed-on probe, thus causing physiological movements within the sound conducting structures (Fig. 3). As a reaction to this kind of stimulation--1000 clicks with a duration of 0.1 ms were given--far field brain stem potentials can be recorded. The calibration of this special sound probe--not bigger than a pencil (Fig. 1)--was made by equalizing the mechanically and acoustically evoked guinea-pig brain stem potentials (Fig. 2). The intraoperative control of sound transmission to the inner ear is ascertained by the mechanically evoked potential's latency and amplitude. In order to apply the procedure in tympanoplasty we made a number of recordings after having simulated various kinds of middle ear pathology in the guinea pig. Four cases of various kinds of ear disease (interruption of the ossicular chain - Fig. 4 -, soft tissue bridge between incus and stapes - Fig. 5 -, otosclerosis - Fig. 6 -, Torp prosthesis - Fig. 7 -) are presented. As a result of our intraoperative recordings we can demonstrate that the presented method may be a valuable contribution to the examination of acoustic transmission through the middle ear during tympanoplasty under general anesthesia.
D000818:Animals; D001299:Audiometry / Q000295:instrumentation*; D001300:Audiometry, Evoked Response / Q000295:instrumentation*; D001307:Auditory Perception / Q000502:physiology*; D001933:Brain Stem / Q000502:physiology*; D006168:Guinea Pigs; D006801:Humans; D014433:Tympanoplasty
Einsatz einer Körperschallsonde und Ableitung von Hirnstammpotentialen zur Bestimmung der Schallübertragung während der Tympanoplastik.