Original Paper

Ultrastructural Changes in Otoconia of Osteoporotic Rats
Dominique Vibert^a, Alain Sans^c, Martin Kompis^a, Cécile Travo^c, Roman C. Mühlbauer^b, Ingrid Tschudi^b, Hassan Boukhaddaoui^c, Rudolf Häusler<sup>a

a</sup>Department of Otorhinolaryngology, Head and Neck Surgery, Inselspital, and
^bBone Biology Group, Department of Clinical Research, University of Bern, Bern, Switzerland;
^cINSERM Institut des Neurosciences de Montpellier, Hôpital St Eloi, Montpellier, France

Address of Corresponding Author

Audiol Neurotol 2008;13:293-301 (DOI: 10.1159/000124277)

  Key Words

• Otoconia
• Osteopenia
• Osteoporosis
• Idiopathic benign paroxysmal positional vertigo, women
• Calcium metabolism

  Abstract

The etiology of benign paroxysmal positional vertigo (BPPV) remains obscure in many cases and women are affected more often than men. A recent prospective study, performed in women >50 years of age suffering from recurrent BPPV, showed associated osteopenia or osteoporosis in a large percentage of these patients. These results suggested the possible relationship between recurrent BPPV and a decreased fixation of calcium in bone in women >50 years. To test this hypothesis, an experimental study was performed in adult female rats. Utricular otoconia of female rats in which osteopenia/osteoporosis was induced by bilateral ovariectomy (OVX) were compared to those of sham-operated adult females rats (SHAM), as control group. First Study: The morphology of theutricles of OVX and SHAM rats was analyzed with scanning electron microscopy. In osteopenic/osteoporotic rats, the density of otoconia (i.e. the number of otoconia per unit area) was decreased (p = 0.036)and their size was increased (p = 0.036) compared to the control group. Second Study: To test the role of calcium turnover in such morphological changes, utricular otoconia of 2 other groups of OVX and SHAM rats, previously injected with calcein subcutaneously, were examined by conventional and epifluorescence microscopy. In epifluorescence microscopy, labeling with calcein showed no significant fluorescence in either group. This finding was interpreted as a lack of external calcium turnover into otoconia of adult female rats. The ultrastructural modifications of otoconia in osteopenic/osteoporotic female adult rats as well as the role of estrogenic receptors in the inner ear are discussed. The possible pathophysiological mechanisms which support the relationship between recurrent BPPV in women and the disturbance of the calcium metabolism of osteopenia/osteoporosis are debated.

Copyright © 2008 S. Karger AG, Basel

  Author Contacts

Dominique Vibert, MD
Neurotology
University Clinic of ENT, Head and Neck Surgery, Inselspital
CH-3010 Bern (Switzerland)
Tel. +41 31 632 33 21, Fax +41 31 632 88 08, E-Mail dominique.vibert@insel.ch

  Article Information

This work was presented as an oral communication at the 24th Bárány Society Meeting in Uppsala, June 11-14th, 2006.

Received: April 27, 2007
Accepted after revision: November 28, 2007
Published online: April 7, 2008
Number of Print Pages : 9
Number of Figures : 6, Number of Tables : 0, Number of References : 50