Document Detail

A mathematical model for top-shelf vertigo: the role of sedimenting otoconia in BPPV.
MedLine Citation:
PMID:  15212918     Owner:  NLM     Status:  MEDLINE    
Benign paroxysmal positional vertigo (BPPV) is a mechanical disorder of the vestibular system in which calcite particles called otoconia interfere with the mechanical functioning of the fluid-filled semicircular canals normally used to sense rotation. Using hydrodynamic models, we examine the two mechanisms proposed by the medical community for BPPV: cupulolithiasis, in which otoconia attach directly to the cupula (a sensory membrane), and canalithiasis, in which otoconia settle through the canals and exert a fluid pressure across the cupula. We utilize known hydrodynamic calculations and make reasonable geometric and physical approximations to derive an expression for the transcupular pressure DeltaPc exerted by a settling solid particle in canalithiasis. By tracking settling otoconia in a two-dimensional model geometry, the cupular volume displacement and associated eye response (nystagmus) can be calculated quantitatively. Several important features emerge: (1) a pressure amplification occurs as otoconia enter a narrowing duct; (2) an average-sized otoconium requires approximately 5 s to settle through the wide ampulla, where DeltaPc is not amplified, which suggests a mechanism for the observed latency of BPPV; and (3) an average-sized otoconium beginning below the center of the cupula can cause a volumetric cupular displacement on the order of 30 pL, with nystagmus of order 2 degrees/s, which is approximately the threshold for sensation. Larger cupular volume displacement and nystagmus could result from larger and/or multiple otoconia.
Todd M Squires; Michael S Weidman; Timothy C Hain; Howard A Stone
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of biomechanics     Volume:  37     ISSN:  0021-9290     ISO Abbreviation:  J Biomech     Publication Date:  2004 Aug 
Date Detail:
Created Date:  2004-06-23     Completed Date:  2005-02-16     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0157375     Medline TA:  J Biomech     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1137-46     Citation Subset:  IM    
Departments of Applied and Computational Mathematics and Physics, California Institute of Technology, Pasadena, CA 91125, USA.
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MeSH Terms
Calculi / physiopathology
Ear, Inner / physiopathology*
Models, Biological
Nystagmus, Pathologic / etiology
Otolithic Membrane / physiopathology*
Semicircular Canals / physiopathology
Time Factors
Vertigo / etiology*,  physiopathology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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