[Clinical significance of preoperative impedance measurements]

On the basis of six particular cases in which the various impairments of the middle ear were verified during the surgical intervention, the authors show how it is possible to obtain by means of the Madsen ZO 70 electroacoustic impedance meter and of the Grason-Stadler Model 1720 otoadmittance meter useful additional information about the preoperative dynamic behavior of the tympano-ossicular system. With regard to the measurement of 'susceptance' and the 'conductance' at 220 and 660 Hz, it permits to establish a better differential diagnostic.