Acoustic Admittance Measurements in Human Temporal Bones

Abstract

Admittance component curves were studied in a series of 14 fresh human temporal bones with perfectly normal tympanic membrane, before and after experimental lesions. The lesions were all performed in successive steps in each temporal bone and consisted in section of ligaments and tendons, interruptions and fixations of the ossicular chain. The results obtained demonstrate that the tympanograms traced in fresh human temporal bones, before and after experimental lesions, are quite similar to those observed respectively in normal and pathological living ears, (a) The ‘pre-experimental’ tympanograms showed A-type curves with peak and admittance component values well within the range of normal living ears; (b) the tympanogram peak values increased very little and remained in the range of normal ears also after section of ligaments and tendons; (c) the ossicular chain interruptions always resulted in A-type curves at 220 Hz and in W-pattern ones at 660 Hz wherever the interruptions occurred; (d) the ossicular chain fixations always exhibited A-type tympanograms with decreased peak and admittance component values; (e) finally, the condition of the Eustachian tube, closed or opened, did not change the shape of the tympanograms; the notch depth of the curves traced with opened tube, became higher than those obtained with closed tube.

Key Words:

• Admittance
• Temporal bone
• Middle ear manipulations
• Probe tone frequencies