PubMed · 9787510
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N Rasmussen. 1998. Eustachian tube function.. https://pubmed.ncbi.nlm.nih.gov/9787510/
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A flat tympanogram predicts a middle ear effusion in about 90% of cases. This paper describes how to perform tympanometry, some common problems when doing it and how to classify the curves in normal (type A), middle ear effusion (type B) or negative pressure (type C). The theoretical background of impedance audiometry is outlined. The stapedius reflex, pneumatic otoscopy, reflexometry and otomicroscopy are described as supplements or alternatives in diagnosing fluid in the middle ear. Tympanometry is recommended as a diagnostic modality for general practitioners.
Otoscopic examination and audiometric tests complement each other for the diagnosis of hearing loss. Objective tests measure the hearing loss at some specific frequencies. Endo- or retrocochlear origin of the deafness is identified thanks to these tests, leading to selection of the most appropriate therapeutic option. In children, behavioral assessment techniques are to be adapted to the patient's age. Information from tympanometry, otoacoustic emissions and possibly auditory brainstem responses, is used to complete the diagnosis. Language skills are also assessed in order to adapt the child's deafness management to his/her actual communication ability.
The sound transmission properties of three different commercially available middle ear implants and the prototype of a complete middle ear prosthesis (CoMEP) were evaluated with a special measurement system that permits standardized conditions. This system uses a mechanical middle ear model (MMM) which approximates the impedances of the tympanic membrane and inner ear. The implants were fitted under defined conditions into the MMM. Displacement of the artificial stapes footplate of the MMM was measured with an optical probe. The measurements of different middle ear prostheses showed that the mass of the implant was the most important factor for optimum high frequency transmission. The lightest implant (4 mg, titanium) showed the best results. The CoMEP revealed the highest sensitivity because of a slight enlargement of the diameter of the artificial tympanic membrane. These findings show that the CoMEP is able to restore sound transmission to a normal range. In a second experiment one of the implants was fitted into the MMM with different forces. The increase of stiffness produced a slightly better high frequency transmission at the expense of low frequency sensitivity. Hence, the fitting of the implant may not be too stiff because of its loss of mobility within a significant frequency range.