Objective: To determine if there is an anatomic basis for the assumption that loose, "rogue" otoliths presumed to arise from the utricular macula and theorized to cause benign paroxysmal positional vertigo (BPPV) by impinging on semicircular canal ampullae could be returned to their original site by a series of changes in the position of the head called particle repositioning maneuvers (PRMs). Further, if such otolith movement were possible, once they were replaced into the utricle, would they adhere to the utricular macula?
Study design: Kodachrome photographs of 2-mm-thick macrosections of human temporal bones were available for evaluation. The bones were sectioned in horizontal, coronal, and sagittal planes. Rice grains were placed on the photographs of the cross-sections to demonstrate the possible paths taken by loose otoliths under the influence of gravity in different positions of the head.
Results: A study of cross-sections of the temporal bone shows that loose macular otoliths after PRMs would tend to fall into the lumen of the utricle. Once the patient assumes the erect position, however, repositioned otoliths would tend to fall into the near or utriculopetal side of the cupula of the posterior semicircular canal, which opens directly into the inferior portion of the utricle, and could cause labyrinth stimulation and BPPV by the same mechanism of misplaced otoliths on the opposite or far side of the cupula. Loose otoliths in the utricle could also stimulate the horizontal ampullae.
Conclusions: PRMs do not remove or fix otoliths in any specific site in the labyrinth. Repositioning of loose otoliths onto the original site in the macula of the utricle, which lies superiorly in the vestibule, could not be accomplished by any of the repositioning maneuvers. If otoliths were to be repositioned on the utricular macula, there is no evidence that the otoliths would adhere to the macula when the patient assumes the erect position. The good results obtained by physiotherapeutic procedures suggest that some other mechanism than repositioning of otoliths is responsible for the relief of BPPV.