A tympanometric approach to otosclerosis

A formula has been elaborated to estimate the resonance frequency of the middle ear from non-simultaneously recorded susceptance and conductance tympanograms at 220 and 660 Hz. The formula is tested on 30 normal and 29 otosclerotic ears. From these experimental results one can conclude that the middle-ear model (proposed by Lutman), from which the formula was deduced, is too crude to assess the resonance frequency. Nevertheless a ratio of phase angles functions at 220 and 660 Hz, introduced in that formula, is always qualitatively linked to the resonance frequency. Experimental data proved that this ratio can be used to distinguish tympanograms from otosclerotic ears with normal tympanic membrane from those obtained from normals. A statistical treatment is proposed to estimate the probability of false-positive or false-negative cases as a function of the value of that ratio.