Preoperative Estimation of Sound-Conducting Apparatus (“Transmission Testing”) In Chronic Otitis

Abstract

As a result of the audiological evolution of the last two decades-both technical-diagnostic as well as medical-therapeutic-it is now possible in most instances of conductive deafness to reduce hearing loss by means of an artificial drum prosthesis or through an operative correction of a part of the sound transmission mechanism, whereas in exceptional cases a hearing aid may be chosen.

1. One hundred cases of chronic otitis with hearing loss have been examined by means of “transmission testing”, that is

(a) optical examination of the middle ear in an operation microscope with 10 power magnification

(b) taking “vibrating probe” audiograms from certain fixed application-points

(c) attempts to reduce the hearing loss through covering prosthesis or round window blocking prosthesis.

2. The vibrating probe is a vibrating needle connected with an ordinary bone conduction telephone. Uniform vibrating probes probably could be available if their physical properties were taken further into consideration and investigated. The threshold value with the vibrating probe from the handle of malleus then might be put together with the air conduction and bone conduction threshold as a third relation threshold, i.e., vibrating probe audiogram.

3. A detailed examination scheme, following a fixed pattern, is set up to facilitate the registering of all possible factors important in middle ear transmission.

4. In the actual study there was good agreement between preoperative estimation and operative verification in cases with drum perforations but without essential adhesions and mucous membrane reactions, since the transmission properties in such cases are favourable to penetrate. On the other hand the mechanism of transmission is more difficult to estimate in cases with more pronounced adhesive processes and secretion.

5. In cases of chronic otitis there are still several unknown facts which determine both the amount of the hearing loss and further the chance of healing (i.e., restoration of hearing).

It seems easier to find out these factors if primarily those cases are operated upon in which the preoperative transmission testing can penetrate the middle ear mechanism rather well.