PubMed · 9340328
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K B Hüttenbrink. 1997. [The middle ear].. https://pubmed.ncbi.nlm.nih.gov/9340328/
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INTRODUCTION: The physiological function of the mastoid air cell system (MACS) with respect to middle ear (ME) pressure-regulation remains controversial because predictive mathematical models and experimental data to formulate and test hypotheses are lacking. OBJECTIVE: A mathematical description of MACS volume effects on the rate of ME pressure change is presented; the agreement between published data and model prediction is examined for consistency with the hypothesis that the MACS acts as a functional rate-limiter of ME pressure change, and an explanation for the relationship between MACS volume and otitis media is discussed. METHODS: The mathematical description shows that the value of a single, free parameter, termed the "MACS buffering efficiency" (M) determines if MACS volume affects the rate of ME pressure change caused by diffusive gas exchange. The MACS serves no rate-limiting function for M=0, acts as a gas sink for M>1 and acts as a gas reserve (rate-limiter) for M<1. RESULTS: Fitting the model equation to published adult human data yielded an estimate for M of 0.2. This implies that larger MACS volumes are associated with lesser rates of change in ME pressure caused by diffusive gas exchange and lesser required frequencies of effective Eustachian tube openings to maintain near ambient ME pressures. CONCLUSION: If well-controlled studies confirm M<1 for children and adults, larger MACS volumes will increase the time required to develop sufficient ME underpressures to cause otitis media by hydrops ex vacuo during transient or prolonged periods of Eustachian tube dysfunction.
Imaging is an essential diagnostic tool in reconstructive middle ear surgery, especially in pre-operative planning. Due to ongoing improvement of imaging quality and development of new imaging techniques like e.g. rotational tomography (RT) post-operative follow-up and immediate evaluation of surgical results may become more important. The aim of this experimental study was to evaluate RT as a new tool for postoperative determination of middle ear anatomy and implant position in temporal bones. RT was performed in ten temporal bone specimen after insertion of different middle ear prostheses concerning material, shape and length (PORP; TORP; Stapes piston). An implantable hearing device (Symphonix Soundbridge) was also implanted and visualized. For comparison some specimen additionally underwent conventional computed tomography (CT), including the newest technology. Characterization of anatomical structures of the temporal bone using RT was of comparable quality to conventional CT-scans in all investigated specimen while requiring approximately 30% of the CT's irradiation exposure. Unlike CT the RT showed almost no problems due to metallic artefacts of the implanted prostheses. Furthermore RT enabled a 3-dimensional view of the temporal bone and angle determination of inserted prostheses towards the tympanic membrane and/or the malleus handle. Detailed imaging of the prostheses allowed determination of shape, material and localization within the specimen's reconstructed middle ear. The new imaging technique of RT allows precise presentation of anatomical structures and middle ear implants in temporal bones. Following these experimental results it will be our future work to evaluate this method in clinical practise.
OBJECTIVE: To describe a unilateral progressive conductive hearing loss caused by incus discontinuity (without erosion of the long process of the incus), and otosclerosis with fixation of the stapedial footplate. STUDY DESIGN: Case report. SETTING: Department of Otolaryngology, Head and Neck Surgery of the University of Rochester Medical Center, which is a regional tertiary referral center. PATIENT: A 54-year-old woman with multiple otologic complaints including tympanic membrane perforations, otalgia, tinnitus, and hearing loss. Audiography demonstrated 100% speech discrimination bilaterally and a significant conductive right-sided hearing loss. INTERVENTION: The patient underwent a stapedectomy, during which a discontinuity between the long process of the incus and the stapes with no bony erosion was identified. The stapedectomy was completed and an ossicular piston prosthesis was inserted to reestablish ossicular continuity with the tympanic membrane. MAIN OUTCOME MEASURE: Improved subjective hearing confirmed objectively by audiography. CONCLUSION: This is the third reported case of an unusual combination of otosclerosis and ossicular discontinuity, and the first such case report in a patient without head trauma. In addition, it adds a unique item to the differential diagnosis of the pathologic features implicated in an ear with a conductive deficit and normal tympanogram.