Otoconia and otolithic membrane fragments within the posterior semicircular canal in benign paroxysmal positional vertigo

Abstract

Objective Benign paroxysmal positional vertigo (BPPV) is the most common vestibular disorder with an incidence between 10.7 and 17.3 per 100,000 persons per year. The mechanism for BPPV has been postulated to involve displaced otoconia resulting in canalithiasis. While particulate matter has been observed in the endolymph of affected patients undergoing posterior canal occlusion surgery, an otoconial origin for the disease is still questioned. Study Design In this study, particulate matter was extracted from the posterior semicircular canal of two patients and examined with the scanning electron microscopy. Methods The samples were obtained from two patients intraoperatively during posterior semicircular canal occlusion. The particles were fixed, stored in ethanol and chemically dehydrated. The samples were and sputter coated and viewed under a scanning electron microscope. Digital images were obtained. Results Intact and degenerating otoconia with and without linking filaments were found attached to amorphous particulate matter. Many otoconia appeared to be partially embedded in a gel matrix, presumably that which encases and anchors the otoconia within the otolith membrane, while others stood alone with no attached filaments and matrix. The otoconia measured roughly 2 to 8 μm in length and displayed a uniform outer shape with a cylindrical bulbous body and a 3+3 rhombohedral plane at each end. Conclusion These findings suggest that the source of the particulate matter in the semicircular canals of patients with BPPV is broken off fragments of the utricular otolithic membrane with attached and detached otoconia. Level of Evidence NA

A mouse model for benign paroxysmal positional vertigo with genetic predisposition for displaced otoconia

“…The first in vivo evidence for “free‐floating particles” was identified during a canal occlusion procedure aimed to abolish endolymphatic flow in the posterior semicircular canal . Additional studies consistently found a particulate matter composed of otolithic membrane and otoconia in the semicircular canals of patients with BPPV …”

Benign paroxysmal positional vertigo

“…The source of the canaliths responsible for the development of disease has been the subject of much speculation, with many theorizing that displaced otolithic membrane fragments may be the culprit. Recent work by Kao et al supports this concept . Scanning electron micrographs of posterior semicircular canal contents extracted from patients with intractable BPPV show free‐floating otoconia with linking filaments attached to what appears to be a gelatinous matrix (Fig.…”

“…Recent work by Kao et al supports this concept. 12 Scanning electron micrographs of posterior semicircular canal contents extracted from patients with intractable BPPV show free-floating otoconia with linking filaments attached to what appears to be a gelatinous matrix (Fig. 2).…”

Horizontal semicircular canal jam: Two new cases and possible mechanisms

“…At the time of surgery for intractable BPPV, two patients were found to have fragments of otolithic membrane and otoconia encased in their gelatinous matrix, putatively sluffed from the otolith organ. It is not hard to imagine that these relatively large chunks of membrane and otoconia could be held up or trapped in various locations inside the membranous portion of the semicircular canals, which themselves almost certainly have some irregularities in their wall, and fluctuate in their circumference . Semicircular canal membrane plugs (jams), even perhaps more than one in a single canal, may be more common than appreciated and might be responsible for other unusual patterns of nystagmus such as persistent geotropic nystagmus with vertigo that currently is attributed to the “light cupula” phenomenon.…”