Document Detail


Analysis of middle ear mechanics and application to diseased and reconstructed ears.
MedLine Citation:
PMID:  9093668     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
OBJECTIVE: To review current concepts of the mechanical processes of the human middle ear, and to apply them to practical issues in clinical otology and tympanoplasty surgery. BACKGROUND: The wide range of conductive hearing losses associated with middle ear pathology and reconstruction cannot be adequately explained by simple models of middle ear function. METHODS: Variables used to describe the system are sound pressure, volume velocity, and acoustic impedance. The relationship between specific middle ear structures and these variables is described such that inferences can be drawn regarding sound conduction in the normal, diseased, and reconstructed middle ear. RESULTS AND CONCLUSIONS: Sound can be transmitted from the car canal to the cochlea via two mechanisms: the tympano-ossicular system (ossicular coupling) and direct acoustic stimulation of the oval and round windows (acoustic coupling). Acoustic coupling is negligibly small in normal ears, but can play a significant role in some diseased and reconstructed ears. In the normal ear, middle ear pressure gain (which is the result of ossicular coupling) is frequency-dependent and less than generally believed. The severity of conductive hearing loss due to middle-ear disease or after tympanoplasty surgery can be predicted by the degree to which ossicular coupling, acoustic coupling, and stapescochlear input impedance are altered. Hearing after type IV and V tympanoplasty is determined solely by acoustic coupling. The difference in magnitude between the oval- and round-window pressures is more important than the difference in phase in determining cochlear input. In tympanoplasty types I, II, and III, adequate middle-ear and round-window aeration is necessary and the tympanic membrane-ossicular configuration may be less crucial.
Authors:
S N Merchant; M E Ravicz; S Puria; S E Voss; K R Whittemore; W T Peake; J J Rosowski
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.; Review    
Journal Detail:
Title:  The American journal of otology     Volume:  18     ISSN:  0192-9763     ISO Abbreviation:  Am J Otol     Publication Date:  1997 Mar 
Date Detail:
Created Date:  1997-06-23     Completed Date:  1997-06-23     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  7909513     Medline TA:  Am J Otol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  139-54     Citation Subset:  IM    
Affiliation:
Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston 02114, USA.
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MeSH Terms
Descriptor/Qualifier:
Acoustics
Cochlea / physiology
Ear Ossicles / pathology,  physiology
Ear, Middle* / physiology*,  physiopathology,  surgery
Hearing Loss, Conductive / diagnosis,  etiology,  physiopathology
Humans
Ossicular Prosthesis
Otosclerosis / pathology
Severity of Illness Index
Tympanic Membrane Perforation / complications
Tympanoplasty
Grant Support
ID/Acronym/Agency:
K08 DC 00088/DC/NIDCD NIH HHS; P01 DC 00119/DC/NIDCD NIH HHS

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