Detection of human utricular otoconia degeneration in vital specimen and implications for benign paroxysmal positional vertigo

Abstract

Otoconia are assumed to be involved in inner ear disorders such as benign paroxysmal positional vertigo (BPPV). Up to now, the distinct structure and morphology of intact and degenerate human utricular otoconia has been only poorly investigated on vital specimen. In this study, human otoconia were obtained from the utricle in five patients undergoing translabyrinthine vestibular schwannoma surgery. Specimens were examined by environmental scanning electron microscopy. Intact and degenerate otoconia as well as fracture particles of otoconia and bone were analyzed by energy dispersive X-ray microanalysis (EDX) and powder X-ray diffraction (XRD). Intact otoconia reveal a uniform size showing characteristic symmetry properties. Degenerative changes can be observed at several stages with gradual minor and major changes in their morphology including fragment formation. EDX analyses reveal the characteristic chemical composition also for otoconia remnants. XRD shows that intact and degenerate otoconia as well as remnants consist of the calcite modification. In conclusion, electron microscopy serves as a standard method for morphological investigations of otoconia. Human utricular otoconia show a uniform outer morphology corresponding to a calcite-based nanocomposite. Morphological changes provide further evidence for degeneration of utricular otoconia in humans, which might be a preconditioning factor causing BPPV. In case of uncertain origin, particles can be clearly assigned to otoconial origin using EDX and XRD analyses.

The Role of Oxidative Stress and Inflammatory Mediators in Benign Paroxysmal Positional Vertigo

“…Calcium and carbonate levels in the endolymph are critical for normal otoconial function, which is primarily provided by a calcium channel transport system expressed in the inner ear [14] . When the ultrastructural dysmorphology of human otoconia was investigated by Walther et al [15] , they found that otoconia may have various degrees of degeneration, from minor to major changes. In the major forms, profound morphological alterations, such as fractures with excessive loss of calcium-rich otoconia material, could be observed.…”

Destructive properties of formalin on human otoconia

“…Some of the images obtained after formalin exposure reveal close structural similarities to degenerate otoconia as described in the literature showing pores and fissures in the belly area as well as fragment formation [3,7,8]. Given the results of this study and previous morphological observations, structural changes of otoconia may, in general, be induced within a short period of time during exposure to previously untested chemical agents [9][10][11][13][14].…”

“…Vital human otoconia were extracted as described recently [3]. Samples lying in the gelatinous matrix were identified by light microscopy (Axioplan 2 imaging, Carl-Zeiss) with a 300-fold magnification.…”

“…Ultrastructural observations of human otoconia together with common analytical methods is the standard method to provide morphological information [3,[7][8][9]. Preparation and preservation of vital otoconia has been inconsistently reported in literature up to now [7][8][9].…”

“…Morphological changes and dislocations of otoconia lead to problems in balance and spatial orientation. Otoconia fragments are assumed to cause benign paroxysmal positional vertigo (BPPV), Ménière's disease and vestibular drop attacks [1][2][3].…”