title: The inner structure of human otoconia.
abstract: BACKGROUND
  The architecture of human otoconia has been only poorly understood up to now. Currently, it is assumed that otoconia contain a central core surrounded by a shell.
  
  
  OBJECTIVE
  To investigate the inner structure of human otoconia.
  
  
  METHODS
  Human otoconia were investigated by environmental scanning electron microscopy (ESEM). The diffraction behavior was analyzed using X-ray techniques (XRD). Focused ion beam (FIB) slices of otoconia were investigated by transmission electron microscopy (TEM). The results were correlated with observations on degenerate human otoconia and decalcification experiments using ethylenediaminetetraacetic acid (EDTA). Artificial otoconia (calcite-gelatine and calcite-gelatine/agarose composites) were investigated in the same way and compared with human otoconia.
  
  
  RESULTS
  Human otoconia represent highly mosaic-controlled calcite-based nanocomposites. The inner structure is composed of 3 + 3 branches with an ordered arrangement of nanocomposite particles and parallel orientation of fibrils. The surrounding belly is less ordered and appears more porous. Degenerate otoconia show a successive dissolution of the belly region exposing to the inner structure (branches) in later stages of degeneration. Artificial otoconia reveal identical chemical, crystallographic and morphologic patterns. They are, however, larger in size.
  
  
  CONCLUSIONS
  Human otoconia show an inner architecture consisting of a less dense belly region and 3 + 3 more dense branches meeting at a central point (center of symmetry). The differences in volume densities and the resulting solubility may play a role in BPPV. Artificial otoconia may serve as a model for further investigations.
authors.affiliation: *Department of Otorhinolaryngology, Head and Neck Surgery, University Medicine Mannheim, Ruprecht-Karls University Heidelberg, Germany; †Department of Otorhinolaryngology, Helios Clinic Berlin-Buch, Berlin, Germany; and ‡Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.
authors.forename: Leif Erik
authors.initials: LE
authors.lastname: Walther
authors.forename: Alexander
authors.initials: A
authors.lastname: Blödow
authors.forename: Marc Boris
authors.initials: MB
authors.lastname: Bloching
authors.forename: Jana
authors.initials: J
authors.lastname: Buder
authors.forename: Wilder
authors.initials: W
authors.lastname: Carrillo-Cabrera
authors.forename: Elena
authors.initials: E
authors.lastname: Roseeva
authors.forename: Horst
authors.initials: H
authors.lastname: Borrmann
authors.forename: Paul
authors.initials: P
authors.lastname: Simon
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Kniep
mesh_terms: D018360:Crystallography, X-Ray; D003648:Decalcification Technique; D007758:Ear, Inner / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008867:Microtomy; D008953:Models, Anatomic; D053761:Nanocomposites; D010037:Otolithic Membrane / Q000033:anatomy & histology* / Q000737:chemistry / Q000473:pathology; D016610:Tissue Embedding