[The complex tympanic membrane impedance in various middle ear disturbances (author's transl)].

Clinical experience with two-component registration (Susceptance and Conductance) of the tympanic membrane impedance at two frequencies (220 and 660 Hz) is reported. More than 1000 results of the last 6 years have been evaluated. The normal tympanometric shape is confirmed by computer simulation. More information about mass and elasticity relations of the middle ear is obtained by the complex registration at 660 Hz. Clinical examples are presented to demonstrate the influence of scars on the ear drum and of a disruption of the ossicular chain. In 77 cases of otosclerosis with stapes fixation, as confirmed by operation, the shape of the pressure-dependent admittance is significantly narrower than in normal hearing ears. For a glomus tumor a pulsation of the oto-admittance following the electro-cardiogram can be shown. In a classification of the tympanometric types the different shapes correspond well to the set of functional finding (normal) ears, otosclerosis, Eustachian tube malfunction, processes of the middle ear cavity, post operation state). The extreme sensitivity of the method, however, produces a small group of unpredictable results for each type. So differential diagnosis is to be done by usual audiometric methods or microscopy of the ear drum.